Proposed Amendments to National Home Energy Rating Standards

Comment #1

Amendment: Amended Lighting, Appliance and Miscellaneous Energy Usage Profiles
Page Number: 2
Comment Type: Technical

Comment:

Is it too late to add a section amending the definition of Qualifying Light Fixtures such that LED lighting can be included along with fluorescents and lights with motion or photo sensors?

Justification for Change:

We are seeing that LED's are being used more frequently but cannot currently contribute to the HERS rating.

Proposed Change:

Qualifying Light Fixture – A light fixture located in a Qualified Light Fixture location and comprised of any of the following components: a) fluorescent or LED hard-wired (i.e. pin-based) lamps with ballast; b) screw-in LED or compact fluorescent bulb(s); or c) light fixture controlled by a photocell and motion sensor.


Comment #2

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Comment Type: Technical

Comment:

Can a section be included that addresses building enclosure airtightness testing in attached multifamily units, similar to the section available for duct leakage testing? Should infiltration used to calculate the HERS index include air leakage from adjacent multifamily units, or exclude that air leakage?

Justification for Change:

If the heat loss algorithms in current rating software assume building air leakage volume is from unconditioned space, this is not a valid approach for attached multifamily units, unless they are tested such that air leakage solely from the exterior is measured. Isolating that air leakage would be a significant task for most HERS raters.

Proposed Change:

I think programs like ENERGY STAR can continue to require the same air leakage rates for single family and attached multifamily since compartmentalization is still important in attached housing. However, the air leakage measured must be addressed differently in the energy model or attached multifamily units will be penalized for air leakage from conditioned space. If that approach cannot be changed, simple guidance on testing procedure is still requested.


Comment #3

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 12
Paragraph / Figure / Table / Note: 803.1
Comment Type: Editorial

Comment:

The furnace nameplate data used in 803.1 should specify the number to be used (input or output)

Justification for Change:

Clarification

Proposed Change:

instead of furnace capacity, 200 CFM per 12,000 Btu/h of furnace (input or output) capacity whichever is greater.


Comment #4

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 8
Paragraph / Figure / Table / Note: 9
Comment Type: Editorial

Comment:

The following paragraph is used twice in this document (Page 8, Paragraph 9 and the end of page 5 and beginning of page 6)

If the altitude is above 5,000 feet or the difference between the inside and outside temperature is more than 30 degrees Fahrenheit then calculate the corrected CFM50 as defined below:
Calculate the Average Corrected CFM50 =
Average Nominal CFM50 x altitude correction factor x
temperature correction factor
where
altitude correction factor = 1 + .000006 x altitude,
altitude is in feet
temperature correction factors
are listed in Table 802.1

Is it or can it be assumed that if the "and" doesn't apply and it is an either/or situation there is to be no correction?

Justification for Change:

Clarification

Proposed Change:

If the altitude is above 5,000 feet or the difference between the inside and/or outside temperature is more than 30 degrees Fahrenheit then calculate the corrected CFM50 as defined below:


Comment #5

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 9
Comment Type: Editorial

Comment:

The best or preferred location of sealing of continuously operating ventilation fans should be specified as it is in Page 3, paragraph 12.

Justification for Change:

To define proper procedure for sealing such fan openings.

Proposed Change:

For continuously operating ventilation systems seal the air opening (preferably seal at the exterior of enclosure)


Comment #6

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 17
Paragraph / Figure / Table / Note: 804.1 & 804.2
Comment Type: General

Comment:

 A balometer capture hood (i.e. Alnor LoFlo) should be an approved method to measure airflow into and out of grilles.

 

Justification for Change:

The balometer is at least as accurate as an exhaust flow bucket and moreso than the plastic bag method.

Proposed Change:

804.1.3 Balometer Capture Hood

A balometer capture hood may be used if the airflow falls within the manufacturer's operating specifications.  Follow the manufacturer's instructions for measuring airflow.

 

804.2.3 Balometer Capture Hood

A balometer capture hood may be used if the airflow falls within the manufacturer's operating specifications.  Follow the manufacturer's instructions for measuring airflow.


Comment #7

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2
Comment Type: General

Comment:

 Section 802.2 should contain a paragraph for adjacent units.

Justification for Change:

 There is debate as to whether adjacent units may or should be simultaneously depressurized during blower door and duct testing.


Comment #8

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 9
Paragraph / Figure / Table / Note: Table 802.1
Comment Type: Technical

Comment:

Some of the table values are incorrect. See 65/65 in pressurization table.

Proposed Change:

Check table values for reasonableness and cahnge where incorrect


Comment #9

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: #4 Attics
Comment Type: Technical

Comment:

Access doors, dampers or vents should NOT be left in their as found position if it is suspected that they were  left that way by mistake or they are in a position that would result in damage to the building from rain water intrusion, pests, etc.

Justification for Change:

Liability to rater/auditor if the house is left in a hazardous condition.


Comment #10

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: #13
Comment Type: Technical

Comment:

If the rater is testing the house in summer and the louvers of a whole house fan are open, they should be closed.  The house should be placed in winter conditions.

Justification for Change:

All blower door guidelines state that the house should be placed in winter conditions.

Proposed Change:

Close louvers/shutters on whole house fans.


Comment #11

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: General comment
Comment Type: General

Comment:

The blower door testing accuracy levels and ACH calculations are too complicated.  Remove the requirements and calculations associated with determing "standard" and "reduced" levels of accuracy.

Justification for Change:

The blower door test is not that accurate an assessment of actual infiltration rates as has been shown in numerous tracer gas studies. The level of accuracy does NOT warrant this level of detail when testing.

Proposed Change:

Simple one point tests should be allowed with special consideration for windy days as described in the blower door manuals.


Comment #12

Amendment: Amended Lighting, Appliance and Miscellaneous Energy Usage Profiles
Page Number: 13
Paragraph / Figure / Table / Note: 803.2.1
Comment Type: Technical

Comment:

Approved blower door testing techniques for multi-family buildings should be addressed.  Are we allowing guarded testing or simply single unit testing.

Justification for Change:

Need clarification and direction on this issues.

Proposed Change:

Add recommendations and procedures for air-leakage testing in multi-family dwellings.


Comment #13

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 13
Paragraph / Figure / Table / Note: third
Comment Type: Technical

Comment:

The last sentence of paragraph 3 says that if all ducts are in conditioned space and visible, ducts don't have to be tested.  ENERGY STAR requires a maximum building air leakage rate as well.  This should also.

Justification for Change:

In contradiction with ENERGY STAR.

Proposed Change:

Make consistent with ENERGY STAR.


Comment #14

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 7
Comment Type: Technical

Comment:

Why seal up combustion air vents for solid fuels? 

Justification for Change:

Intentional openings.  Should be left open during testing.

Proposed Change:

Do not seal up combustion air vents.


Comment #15

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 9
Comment Type: Technical

Comment:

This is nit-picky, but include continously operating vent fans in your list of thinkgs to turn off.  Wouldn't want them sealed up while they are operating. 

Justification for Change:

Clarification.

Proposed Change:

Include continously operating vent fans in your list of thinkgs to turn off


Comment #16

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 18
Comment Type: Technical

Comment:

Dryer vents should be taped off if a dryer is not installed. 

Justification for Change:

Dryver vents do not leak the same when the dryer is hooked up.

Proposed Change:

Require that dryer vents are taped if the dryer is not present.


Comment #17

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 13
Paragraph / Figure / Table / Note: 3
Comment Type: Technical

Comment:

Will ducts in conditioned space be input as 0 cfm25 in modeling software?

Justification for Change:

Clarification

Proposed Change:

Please clarify how duct leakage should be input if they are not tested because they are in conditioned space.


Comment #18

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 13
Paragraph / Figure / Table / Note: last
Comment Type: Technical

Comment:

To ensure that the furnace doesn't turn on during the test, throw the emergency kill switch at the AHU or set the heating/cooling switch to off.

Justification for Change:

Clarification.

Proposed Change:

Just clarify to the rater how to make sure the fan doesn't come on.  The fan switch only has on/auto options usually.  Just reword this so they know which controls to use.


Comment #19

Amendment: Amended Lighting, Appliance and Miscellaneous Energy Usage Profiles
Page Number: 8 of 21 (original) 1 of 2 (posted changes for review)
Paragraph / Figure / Table / Note: Table 303.4.1.7.2.5(1) and (3)
Comment Type: Technical

Comment:

I agree with the changes that have been proposed to allow AV to be estimated from nominal volume.   However, there is a discrepancy in the refrigeration types supported in each table.  tabse Table 303.4.1.7.2.5(1) has only three basic types (with TDI being an option that does not affect the AV calculation): Top Freezer, Side-by-side, and Bottom Freezer.   Table Table 303.4.1.7.2.5(3) has three additional types: Single door R/F, Single-door R only, and standalone Freezer.   In addition it has a category for "unknown type".  

 

Justification for Change:

 The two tables should be harmonized to cover the same range of refrigeration types.

Proposed Change:

The two tables should be harmonized, either by eliminating the extra categories from Table ...(3) or adding missing categories to Table ...(1). I would suggest adding the following rows to Table ....(1):

Single-door Refrigerator or R/F: (13.5*AV + 299) * VR

Upright Freezer Manual defrost: (10.3*AV + 264) * VR

Upright Freezer Auto defrost: (14*AV + 391) * VR

Chest Freezer: (11*AV + 160) * VR

(Source: 1993 Federal standards)

Also, I would propose eliminating "unknown types" from Table ... (3)--there is no corresponding default energy use calculation for "unknown type". I believe if no actual refrigerator exists in the rated home (e.g. unoccupied) that the rated home refrigerator use would be equal to the reference home use.

Notes: The proposed value for single-door units use the 1993 formula for manual defrost (much more common), even though the 1993 standard had two categories (the other was for partial auto-defrost). The distinction is not obvious in the field and the differences are small: in fact, the two categories have the same requirements as of the 2001 Federal standard. In Table... .(3) the distiction between refrigerator only or Fridge/freezer can remain, since that is an easily visible distiction (though the difference is trivial).

The proposal has three different categories for freezers, because the varying federal minimums result in substantially different energy use. Also, the three types are easily identifiable in the field. All would use the same factor from Table ....(3) under "freezer" to determine AV.

 


Comment #20

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 19
Paragraph / Figure / Table / Note: Background/Rationale
Comment Type: General

Comment:

I agree with the basic rationale written on page 19, however: I would question whether or not there's an actual 'accuracey' issue now? My understanding of accuracey related to 'testing', is the ability to repeat the results.

We already have a QA/QC process in place to do just that. Unless the current QA/QC delegate for a given Provider is finding errors in the testing that impact the accuracey of the 'Rating', I would question the need for calling out 'accuracey levels' and the requirements as spelled out in this proposed Chapter 8.

Require setup and testing per manufacturers user manual. No need to go any further. Additional time and paperwork does not make the home any better.

"If" it is established that Resnet still feels that there is an issue with 'accuracey', then eliminate the one-point testing all together as well as sampling of homes. Require a multi-point test and corresponding software report. Now you'd have computer generated reporting and on 'every home'. Can't get much more accurate than that.

I would also suggest that a Provider be allowed to use their disgretion in implementing any new testing Standard(s) unless their QA/QC has shown there is an actual problem with accuracey outside the limits in the proposed standard. Resnet can always verify this through their Provider QA/QC.

"Because' we can make things more technical in nature, does not generate a 'need to do so'.

Joe Nagan-Home Building Technology Services-Wisconsin

 


Comment #21

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3 section 802.3
Paragraph / Figure / Table / Note: entire section
Comment Type: Technical

Comment:

In many cases the accuracey may not impact the Rating in question. As with Duct Testing, there's a "DEFAULT" mode. No one seems to have an overall 'acuracey' issue using this default by choice where it doesn't impact intended results for Program Qualification.

Why not have the software modified in the infiltration screen to allow the choice for accuracey hereas with duct testing for tightness? Have a toggle for Standard accuracey which would then trigger the Chapter 8 requirements (in final form) AND have a toggle for Reduced accuracey whereby the software internally manipulates the entered CFM/50 number.

It's already noted( item #2) that Resnet accredited software SHALL internaly adjust numbers for 'reduced level of accuracey'. This would save time and reduce the need for more paperwork.

As with duct testing, CFM/50 numbers could be examined at BOP stage to determine whether or not higher accuracey levels as described would be necessary.

Joe Nagan- Home Building Technology Services-Wisconsin


Comment #22

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: all 'procedural pages'
Comment Type: Technical

Comment:

Will there now be a standardized form for all the recording that will now be required as a result of this Standard? If so, who will generate this? There will need to be places to record building configuration, equipment and baselines.

Wherever equipment type and serial numbers are required, there should also be a requirement to include the recording of 'manometer' type and serial number.

Justification for Change:

record ALL equipment used in testing not just the fan.

Proposed Change:

include the requirement to record manomter type and serial number as well as fan info.


Comment #23

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 14
Paragraph / Figure / Table / Note: paragraph 1 number 8
Comment Type: Technical

Comment:

Zone and bypass dampers are not always able to be set in the 'open 'position during testing for a variety of reasons. Since the returns in a zoned system are NOT dampered, is this #8 necessary 'if' testing the entire syatem as a whole? (not seperate return/supply)

Joe Nagan-Home Building Technology Services-Wisconsin


Comment #24

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 18-19
Paragraph / Figure / Table / Note: 804.1.2
Comment Type: Technical

Comment:

804.1.2 mentions 'user fabricated box'. This is very general and I am concerned about the accurcey of such devices. Suggest when using 'user fabricated' devices that it be required that Provider check for reasonable accuracey against a known testing method.

I realize this Chapter is intended to establish 'Standardized Methods' for ventilation testing, but I feel there should still be some reasonable requirement for accuracey.

804.2.2 The use of the Bag-Inflation method only would require this be done on the outside of a building at the 'exit point'. This process can be done also by 'deflation' of the bag. Having said this, I do NOT personally feel comfortable with including this procedure in the Resnet Standards. By default, the Resnet standards require the purchase of 'manufactured' reputable equipment for all othet testing. This testing procedure should follow suite.

Showing up on a job site with a garbage bag would probably not do much for credibility and raise more questions. This process was developed in Canada where 'conventional' equipment was not available. To my knowledge, this was not intended to be the standard equipment to be used.

Joe Nagan-Home Building Technology Services-Wisconsin

Proposed Change:

Require Provider approval of 'user fabricated' flow boxes

Remove 804.2.2 option.


Comment #25

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 1
Paragraph / Figure / Table / Note: 801
Comment Type: General

Comment:

Section 801 talks about the tests that Chapter 8 discusses. Although these need to be standardized I am hopeful that this is just a start. Raters work within the confines of a number of programs that require testing that goes beyond the direct creation of an Energy Rating but need to be defined and standardized so that a Rater can point to a single place for how to perform a test. Energy Star V3 for example is asking Raters to do Room pressures testing and Static pressure testing. After performing these tests many times it has become apparent that Raters and HVAC contractors have different expectations of how the test should be performed. Therefore a national standard is needed and I feel they are needed for the following tests.
• Room pressures measurements
• Static pressure measurements
• Flow hood measurements and balancing at supply and returns
• Heat Rise measurements
• Flow plate measurements
 

Justification for Change:

National programs are requiring these test and often that Raters either perform them or review the results of them.  There are no National standards on how to perfrom them.

Proposed Change:

EnergyLogic has written policies on how to perfrom many, but not all, of these tests.  WE would be happy to provide what we have as a starting point for discussion.


Comment #26

Amendment: Amended Lighting, Appliance and Miscellaneous Energy Usage Profiles
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 #9
Comment Type: Technical

Comment:

802.2 #9 Some fans such as a hard wired exhaust fan utilized for a whole house controlled mechanical exhaust ventilation strategy are impossible to shut off during a blower door test. Our experience is that they do not skew the test results significantly for the purposes of a Rating. We would do not want to tape over them as this can stress the motor and therefore feel they should be exempt from the need to disable for the test.

Justification for Change:

802.2 #9 Some fans such as a hard wired exhaust fan utilized for a whole house controlled mechanical exhaust ventilation strategy are impossible to shut off during a blower door test. Our experience is that they do not skew the test results significantly for the purposes of a Rating. We would do not want to tape over them as this can stress the motor and therefore feel they should be exempt from the need to disable for the test.

 

Another example in our market is a structural sub floor fan which is hard wired and can not be turned off or taped over.

Proposed Change:

I propose that a continuously running fan, with a CFM rate of 100 CFM or less, be exempt from turning off during a blower door test as the house is designed to operate with the fan running continuously just as it is designed to operate with other opening to the outside that we do not tape off.


Comment #27

Amendment: Amended Lighting, Appliance and Miscellaneous Energy Usage Profiles
Page Number: 13
Paragraph / Figure / Table / Note: 803.2
Comment Type: Technical

Comment:

"When ducts are in conditioned space, 100% of the system is visible and the system is fully ducted (i.e., no building cavities are used to transport air) the ducts do not have to be tested and the ducts may be assumed to have no leakage to outside the conditioned space."

I do not believe this is consistent with other programs. I believe they also require that the house have a certain level of tightness. I believe that it would be good to be consistent with other programs or standards if they are available.
 

Justification for Change:

Consistency

Proposed Change:

Double check Energy Star and other programs for consistency.


Comment #28

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 14
Paragraph / Figure / Table / Note: 803.3 #2
Comment Type: Technical

Comment:

Turn off any fans that could change the pressure in either the conditioned space or
any spaces containing ducts or air handlers (bathroom fans, clothes dryers, kitchen
vent hood, attic fan, etc.).

Justification for Change:

Again – there are fans that are hard wired and run continuously at a low CFM rate like Exhaust ventilation systems or Structural floor fans or Radon fans. I believe the do not significantly impact the test and do not need to be turned off.

#5 in this section says do not tape off an intention opening so I would view a continuously running fan at an intentional designed configuration of the house and that it should not be turned off. In fact it may not be possible to turn it off and may damage the fan to block it off while under power.
 

Proposed Change:

May continusouls running fans exempt.


Comment #29

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 17
Paragraph / Figure / Table / Note: 804
Comment Type: Technical

Comment:

804 ON-SITE INSPECTION PROCEDURES FOR VENTILATION AIR FLOW TESTING
The three testing methods described in this section (power flow hood, air flow resistance, bag inflation) all have issues. As this is the case we would like to recommend a fourth option be added as it has issues as well but is equally as valid a method as the ones described.

Justification for Change:

Although these testing techniques work well for typical path fans we find issues with them for measuring whole house controlled mechanical ventilation systems. As this is the flow that is required for a Rating we need methodologies that will work and is as repeatable as possible. Predominantly the issue we find is the ability to measure the flow of a whole house ventilation system at the air inlet from the outside of the house when wind will interfere with the ability of the capture device to work. Not sure how a bag will capture this flow rate at all.

Proposed Change:

We recommend that an additional option be added to the mix.
Measurement of flow volume in ducts using DG700 and Pitot tube.

To accurately measure CFM in a duct there are a number of items that need to be known.
1. Size of the duct and therefore its cross section area.
The size is gained from visual inspection and the area can be calculated using Pi r2 in feet.
2. The velocity flow of air in the duct.
Through the proper use of the DG700 and Pitot tube the flow can be measured directly.

Once these two are know there sum provides the CFM of the duct.

EnergyLogic has a procedure written up for this technique which we would be happy to provide for discussion and comment.
 


Comment #30

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 #2
Comment Type: Technical

Comment:

Testing with exterior garage doors closed could give a false impression that the house/garage wall is 'tighter' than it actually is. 

Justification for Change:

Intent is to test air tightness of wall between house and garage.  My experience has been that infiltration can be quite different with exterior garage door open and closed.  Many families leave exterior garage doors open frequently. Concentrated indooor air pollutants from a closed garage are a concern.  Therefore, 'worst case' infiltration of the house/garage wall should be considered.

Proposed Change:

Exterior Garage door be opened for testing.


Comment #31

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 #3
Comment Type: General

Comment:

'Conditioned' crawls seldom have accesses or hatches from the house.  Therefore, they are usually outside the zone of depressurization and the crawl walls aren't really tested for infiltration.  This can result is some leaky crawl walls passing an airtightness test.

Justification for Change:

Leaky crawl walls can pass an airtightness test.  'conditioned' crawls generally seem to be over conditioned anyways.  Over conditioning into a leaky space just seems like a further inefficiency.

Proposed Change:

I'm not proposing a change as I can't think of a good testing procedure to address the problem.


Comment #32

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 13
Paragraph / Figure / Table / Note: section 803.2
Comment Type: Editorial

Comment:

Conditioned spaces are not always pressurized by the blower door during a leakage to the outside duct test.  Example: 'conditioned' crawls where there is no access or hatch to the from the house to the crawl.              

Justification for Change:

Accuracy

Proposed Change:

...leakage to the outside only refers to leaks to outside the air pressure boundary.


Comment #33

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 14
Paragraph / Figure / Table / Note: 5
Comment Type: Editorial

Comment:

Section 803.3.5: “Any intentional openings into the duct system such as combustion air or ventilation ducts shall be left in their normal non-ventilation operating position. Motorized dampers should be closed.”

This is poorly worded and can lead to confusion. Combustion air should not be coming in through the duct system. Combustion air ducts and ventilation air for IAQ should be treated separately.

Combustion Air ducts contribute to infiltration and should be left open during blower door testing. 

Ventilation air ducts for IAQ should be sealed (dampers closed and exterior inlets temporarily sealed if accessible) since this is intentional duct leakage.

Justification for Change:

Reduce confusion and provide clarification

Proposed Change:

"Any intentional openings into the duct system such as ventilation ducts for IAQ shall be temporarily sealed by closing dampers and exterior inlets if accessible.  Motorized dampers should be closed."


Comment #34

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 14
Paragraph / Figure / Table / Note: 803.3 item 5
Comment Type: Technical

Comment:

My comments pertain to duct testing setup -- the standard references ASHRAE std. 152 and the RESNET new chapter 8 says the exact oppostite of AHHRAE 152 and this difference is not listed in the exceptions. We need clear not conflicting directions to teach raters and to provide for them for QA of their work.

Verbage copied from both documents

==============================

803.2 RESNET Simplified Test Procedures:

803.3 Protocol for preparing the building and the duct system for a duct leakage test (Items 1-8 are used for both Total and Outside Leakage tests):

5. Any intentional openings into the duct system such as combustion air or ventilation ducts shall be left in their normal non-ventilation operating position. Motorized dampers should be closed.

From New Appendix A rewrite 01262011
Duct Leakage
Any intentional openings into the duct system such as combustion air or ventilation ducts shall be left in their normal non-ventilation operating position. Motorized dampers should be closed.

Duct Leakage
=============================================
exceptions to ASHRAE 152 --Former Appendix A -page A-28

The application of ASHRAE Standard 152 for testing of ducted distribution systems shall be implemented with the following additions and exceptions:
1. Air Handler Fan Flow Measurement using either of the methods specified in Annex A of the standard is preferred. If such measurement is not made, default values of 275 CFM per 12,000 btu/hour of nominal HVAC capacity shall be used. For fossil-fired furnace systems, a default value of 200 CFM for every 12,000 btu/hour of nominal furnace capacity shall be used for heating.
2. Supply and return leakage may be determined by measuring the leakage of each side as in Annex B, or as an alternate the leakage of the entire system may be measured, with the duct pressurization device in the return and the duct-pressure probe in the supply side. The ratio of supply side leakage to return side leakage Q25,s to Q25,r shall be selected separately for heating and cooling based on a worst case determination. The supply side of the system shall be assigned 67% of the leakage and the return shall be assigned 33%, and the overall distribution efficiency determined; then the efficiency with the reverse conditions (67% return and 33% supply) shall be determined, and the lower of the two efficiencies will be applied.
3. Total leakage (Annex C) . The limitation of applicability of Annex C (Section C1) to leakage measurement of 10% or less of air handler air flow shall be based on tested air flow or default air flow, as appropriate according to (1) above. The calculations of 2.5% of air flow in Section C1.1,2, and 3 shall use tested air flow,
===========================================

ASHRAE 152
ANNEX B
DUCT LEAKAGE TO OUTSIDE FROM FAN PRESSURIZATION OF DUCTS AND BUILDING B1 TEST PROCEDURE (last sentence from paragragh #2)
Any intentional ventilation intakes to the return ducts shall be closed or sealed during fanpressurization and operating pressure testing. and from C2 TEST PROCEDURE Any intentional ventilation intakes to the return ducts shall be closed or sealed during testing.

================================================

A second comment/ question that several of the raters that we provide for may have -- pertaining to the same set up proceedure is --

If local/city  code requires a passive air intake to return ducts, known sometimes as "make up" air , does this local code superceed RESNET rules and allow sealing of these intential openings for duct testing?(like 152 says TO do and RESNET say NOT to)???

Justification for Change:

This tells raters to do 1 thing one place and the opposite thing in the other standard. No exception or difference is listed in the RESNET document.

We are giving conflicting instructions and not acknowledging that there is even a difference.

Proposed Change:

List the difference as one of the additions and expeptions to ASHRAE 152 or remove ASHRAE 152 as a standard.


Comment #35

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: Infrared Imaging System Performance
Comment Type: Technical

Comment:

Current language:
Some imaging systems that meet the specifications may have fixed focus and
automatic level and span adjustment. It is the responsibility of the thermographer to
adjust their viewing position relative to the envelope surfaces to ensure that data is of
acceptable quality and the image is properly documented.

Justification for Change:

It is just as important for a thermographer using a manual focus camera to focus their
images as it is for one using a fixed focus camera to position themselves appropriately. The proposed language lends consistency to the intended message.

Proposed Change:

Some imaging systems that meet the specifications may have manual focus, fixed
focus and automatic level and span adjustment. It is the responsibility of the
thermographer to adjust their viewing position and focus relative to the envelope
surfaces to ensure that data is of acceptable quality and the image is properly
documented.


Comment #36

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: Resolution
Comment Type: Technical

Comment:

Title of section could be misconstrued.

Justification for Change:

The term “Resolution” might be construed as referring to either spatial or image resolution. This section clearly refers to Thermal Resolution or, more commonly, Sensitivity.

Proposed Change:

Change title for section from "Resolution" to "Sensitivity" ("Thermal Resolution" would also be acceptable).


Comment #37

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: Resolution
Comment Type: Technical

Comment:

Defining a specification with at a specific ambient temperature might steer buyers toward a camera whose specification is defined at that temperature when in fact they might be better served by a camera whose specification is defined at a lower temperature. The proposed language allows for manufacturers to define their specifications at lower ambient temperature and removes potential confusion for members who might not understand how to determine which of two different specifications (at different ambient temperatures) is better.

Justification for Change:

Other countries are developing standards that recognize the importance of specifications that are defined in accordance with lower ambient temperatures. Canada, for instance, requires specifications that are defined at 0°C (a very reasonable ambient temperature for a northern winter climate). If we are recommending higher temperature deltas as a best practice for residential energy audits, we would be doing our members a disservice by limiting our standard to a specification that is defined at an unreasonably high ambient temperature.

Also, the sensitivity profiles for long-wave cameras differ dramatically from their midwave counterparts. This specification should be applied to long-wave cameras only.

Proposed Change:

The Noise Equivalent Temperature Difference (NETD), which is a measurement of thermal resolution or sensitivity, must be less than or equal to 0.10°C at 30°C or lower. (Note: this specification pertains to Long-wave cameras only).


Comment #38

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: Field of View
Comment Type: Technical

Comment:

Current language reads:
The FOV should be capable of showing at least two wall-framing cavities across while still being able to resolve an individual framing member. In order to accomplish this prerequisite, a FOV of approximately 20 degrees is suggested.

Justification for Change:

“Approximately 20 degrees” is inconsistent with the notion of wanting to see “at least
two wall framing cavities” and could be misconstrued by a novice as being a target
number, rather than a minimum. If the objective is to encourage folks to buy cameras
that can see as many stud bays as possible, the proposed language would be more
precise.

Proposed Change:

The FOV should be capable of showing at least two wall-framing cavities across while still being able to resolve an individual framing member. In order to accomplish this prerequisite, a minimum FOV of 20 degrees is suggested

Other suggestions that would improve the precision of the language usage include:

The FOV should be capable of showing at least two wall-framing cavities across while still being able to resolve an individual framing member. In order to meet this requirement, a minimum FOV of 20 degrees is recommended


Comment #39

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: page 14
Paragraph / Figure / Table / Note: 803.4 #1
Comment Type: Technical

Comment:

"When testing a duct system with 3 or more returns, installation of the duct leakage
tester at the air handler cabinet may be a better attachment location."

add "if the air handler is outside the pressure boundary of house then leakage to outside cannot be tested at the air handler, as the duct tester is then outside the pressure boundary of the house making equalization of duct pressure with house pressure inaccurate."


Comment #40

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3-6
Paragraph / Figure / Table / Note: Accuracy discussion
Comment Type: General

Comment:

There have been several comments concerning the accuracy required for airtightness testing.  I agree with other commenters that the degree of accuracy in the proposed standard is unneccessary.  There is a time and place for accuracy of testing, but rating industry is not it.  With 500,000 new construction units last year and millions of existing housing stock and an industry moving towards mandatory testing, Raters need a test which is quick and relatively accurate.  The more involved baseline reading, temperature adjustment, and altitude adjustment, though not difficult, all complicate testing and take time.  A high volume rater, testing 600 homes per year for example, will spend an additional 10 hours a year just taking baseline measurements that take a minute longer than usual. 

Justification for Change:

Unneccessary.  I would like to see studies or data on testing accuracy and a discussion of the balance of accuracy vs moving the entire housing stock towards greater efficiency.  At what point does the amount of accuracy and modeling involved start to hinder the industry.

Proposed Change:

Keep present accuracy levels with special consideration for Windy days.


Comment #41

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: NA
Comment Type: Technical

Comment:

The Standard is lacking some key testing procedures for measuring ventilation and house pressures.

Justification for Change:

The lack of standard procedure in the testing circumstances below would create a gap in having a standard testing of building performance across the industry.  Current rating requirements and changes to the requirements in ENERGY STAR version 3 require raters to perform tests in some circumstances where the current form of Chapter 8 does not address.  The proposed changes below are areas that should be covered in Chapter 8.

Proposed Change:

Need a standard for flow measurement inside a ventilation duct when the intake is not accesible (gable end above roof). One option is using a pitot tube and flow measurement configurations of the pressure gauge.  Energy Conservatory has a testing procedure for measuring flow inside a duct that would cover this circumstance where the intake is not accesible, but the duct is.

Need a standard for measuring air handler fan watts.  Many manufactuers do not provide this information, however this can be measured by a rater with a standard procedure.

Need a standard for pressure diagnostics for CAZ pressures, house pressures, room to room pressures.


Comment #42

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 18
Paragraph / Figure / Table / Note: 804
Comment Type: General

Comment:

I applaud the addition of ventilation flow testing procedures.  These are becoming more and more necessary as skills every rater should have.  Many of the EEPs require ventilation flow testing and it is nice to have procedures in the standard for that reason.  Still, I feel the proposed amendment leaves out one of the better options for flow testing.  We  have used a procedure for testing flow with a pitot tube and digital manometer using its velocity function.  This procedure came from the Energy Consrevatory.  In instances where the flow hood would have to be applied on the outside of the house (as in testing Air Cycler flow) windy conditions can make the test impossible.  With the pitot tube method, we perform the testing indoors and wind is much less of a factor.  Plus, we don't have to carry around a bunch of extra (and expensive) gear.

My second comment is that room pressures and zonal pressure testing seems to have been ommitted from this proposed standard.  With programs requiring these tests, it seems like something that should be addressed.

Justification for Change:

National Energy Efficiency Program Requirements

Proposed Change:

Add the pitot tube/velocity test as an alternative procedure for measuring ventilation flow.

Add room pressure and zonal pressure testing procedures.


Comment #43

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2
Comment Type: Editorial

Comment:

For the purposes of 802.2.3 and 802.2.4, conditioned attic and crawlspace should be referenced to RESNET 2010-02 "Definition of Conditioned Floor Area."

Furthermore, since insulated attics and crawlspaces generally do not meet the definition of conditioned floor area, these sections should be rewritten from that perspective.

Since an insulated attic or crawlspace is within the thermal boundary, and presumably within the pressure envelope, it is not surprising that there's confusion as to how to handle these spaces in rating and compliance calculations. An argument can be made that blower door testing *should* include these spaces, even though they may not qualify under RESNET's conditioned space definition. If this is the intent, then Section 802.2 should use a different word (other than conditioned) to qualify a crawl or attic for inclusion in the test.

From a practical standpoint, a crawlspace with no access between house and crawl cannot be intentionally pressurized, even if it satisfies the requires of 2010-02 (e.g., over 5 feet in height and 'fully ducted'). What then?

Justification for Change:

Practitioners will misapply the intent of these two sections in the case of an indirectly or minimally conditioned attic or crawl space. We should use every opportunity to reinforce the RESNET interpretation of conditioned space in order to dispel widespread misunderstandings.

Proposed Change:

Revise sections 802.2.3 and 802.2.4 as appropriate, and add footnote referenced to the word conditioned as follows:

"Conditioned floor area does not include spaces such as insulated basements, crawl spaces or attics that are unfinished, if there is no intentional HVAC supply, or minimal supply (inadequate to be considered directly conditioned space). Refer to RESNET 2010-02 Definition of Conditioned Floor Area for further information."

David Butler, Optimal Building Systems

 


Comment #44

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.2.18
Comment Type: Editorial

Comment:

If no dryer is installed and the dryer vent is taped off or otherwise blocked (good practice), then it should be left that way during the test.

Justification for Change:

clarification

Proposed Change:

New text:

"For test purposes, if a dryer is not attached, the dryer exhaust opening should be left in the condition in which it was found. If it is unsealed, this fact should be noted in the test report."


Comment #45

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 1
Paragraph / Figure / Table / Note: Airtightness testing in multi family
Comment Type: General

Comment:

I would like to see precedures in the standard that address whole building testing of multi family buildings.

Justification for Change:

whole building testing has it's benefits and is a good alternative to unit testing.

Proposed Change:

Include section on whole building testing of multifamily buildings for airtightness testing.


Comment #46

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 804.2
Comment Type: General

Comment:

Powered flow hoods or bag inflation methods will not work on fresh air supply ventilation terminating in a house return or unit return plenum.  Intakes are usually inaccessable and can't be tested.

Justification for Change:

Air flow meters just as accurate as bag inflation method?

Proposed Change:

include air flow meters or other alternatives to testing air flows out of grills.


Comment #47

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 12
Paragraph / Figure / Table / Note: Table 803.1
Comment Type: Technical

Comment:

I don't have a copy of ASTM E1554-07, Method A: DeltaQ, but the note restricting this method to buildings with "less than 2500 CFM @ 50 Pa" seems problematic since it does not take size of the building into consideration. Shouldn't this threshold refer to a size nomalized metric such as ACH50 or better yet, ELR? (envelope leakage ratio)

Proposed Change:

Change DeltaQ acceptance threshold to a size normalized metric such as ELR or ACH50

David Butler, Optimal Building Systems


Comment #48

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 13
Paragraph / Figure / Table / Note: 803.2, last pargraph
Comment Type: Technical

Comment:

Without further clarification, a practitioner following this guideline might consider ducts in a sealed attic as being inside conditioned space (refer to previous comment #43 regarding confusion over classification of an insulated attic as conditioned space).

Clearly, ducts located in an insulated crawl or attic should be tested for leakage. Further clarification is necessary.

Also, add commas and clean up wording for clarity.

Justification for Change:

clarification

Proposed Change:

Revise section 803.2 as follows:

"When ducts are in conditioned space as defined by RESNET 2010-02, 100% of the system is visible, and the system is fully ducted (i.e., no building cavities used to transport air), the ducts do not have to be tested and may be assumed to have no leakage to outside."

David Butler, Optimal Building Systems


Comment #49

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 13
Paragraph / Figure / Table / Note: 803.2.1
Comment Type: Editorial

Comment:

Section 802.3.1 references sections 805.4 and 805.6. These are not valid sections.

Also, the following sentence seems incorrect:

"...for energy audits, it is assumed that the leakage to outside is one-half the result of this measurement and that the supply and return leakage are each equal to one-half of the leakage to outside."

Why take one-half of the result when the measurement being referenced *is* the leakage-to-outside test?


Comment #50

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 11 & 12
Paragraph / Figure / Table / Note: Paragraph 803 and Table 803.1
Comment Type: Editorial

Comment:

point out that total duct leakage may be used in place of leakage to outside for purposes of passing a compliance threshold, and may be entered into software as leakage to outside.

Justification for Change:

the software specifies leakage to outside, but the standard doesn't tell you where to enter the total leakage numbers. This is a regular training issue, because previous interpretations have not clarified this.

Proposed Change:

"the total leakage may be used instead of leakage to outside for determining that a system meets a required threshold, and may be entered into the software as leakage to outside in those cases."


Comment #51

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3 - 11
Paragraph / Figure / Table / Note: Section 802
Comment Type: General

Comment:

Please not require precision to 1 CFM and .1 Pa, or expect equal precision in adjustments for altitude, temperature, and etc.

Justification for Change:

This high level of precision will not be repeatable for QA purposes, will be difficult to train, thus becoming onerous to the entire system, and is not merited by accurate results in the software, or by meaningful effects on the index. Using the baselining method described, averaging sequential 10-second-averaged readings, yielded variations of greater than .1 Pa (much greater, sometimes) during casual testing last weekend. Picking "flow@50" on the manometers I use will also frequently give numbers that vary at the same house pressure reading, by much more than 1 cfm. Furthermore, legitimate configuration changes will likely produce differences well beyond these thresholds.

If it's difficult to train and difficult to reproduce, it will be prone to error and useless to enforce.

Proposed Change:

drop the precision targets, and probably drop the correction details, unless they meaningfully affect the software's results.


Comment #52

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 - 6
Comment Type: Editorial

Comment:

Suspended ceiling tiles only need to be moved if there is a risk to the ceiling through pressurization/depressurization. Qualification of "shall" should be included to allow for the Rater's best judgement.

Justification for Change:

In the example given, "Shall" creates a non-compliance with the standard even if there is no chance that the ceiling will be affected (e.g. a SIPS 2 story home with the 1st floor ceiling fully isolated from the outside leakage pathways. unnecessarily moving tiles risks breakage.

Proposed Change:

"Suspended grid ceiling: One tile shall be removed to provide pressure relief and avoid damage during induced pressure differences, as needed."


Comment #53

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 18, 19
Paragraph / Figure / Table / Note: 804.22 Bag Inflation
Comment Type: General

Comment:

Thank you for including Bag Inflation. It is a cost effective and useful method for measuring register outflows.

Justification for Change:

I just want to say again: nice job including the bag inflation method. Other comments disparage it, but we have found it useful, pretty repeatable, and decently accurate (as compared with other accepted tools)

Proposed Change:

None


Comment #54

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 1
Paragraph / Figure / Table / Note: 801 Background
Comment Type: General

Comment:

This submission is primarily by Myron Katz. Much of it was reviewed by others. There are a few comments by David Goldstein which he made two days ago (relative to April 1). I have responded to his questions herein as well.

1
Amendment: Add Chapter Eight to RESNET Standards
Proponent:
RESNET Technical Committee
Applies to:
2006 Mortgage Industry National Home Energy Rating Systems Standards
Proposed Amendment: Chapter Eight as follows:
DRAFT
Chapter 8
RESNET Standards
800 RESNET Standard for Performance Testing and Work
Scope: Enclosure and Air Distribution Leakage Testing
801 BACKGROUND
This Standard will present a step-by-step approach for how to measure:
• enclosure air leakage for the inspection of low rise, three stories or less,
residential and light commercial buildings, and
• duct leakage associated with HVAC systems, and
• air flows for ventilation systems
 

Justification for Change:

The types of comments will be associated with these issues

1.clarity E.G. Where hyphens are needed as suggested.

2. Choice of better terminology to help communicate. E.G. change the name of time averaging period to TEST-AVERAGING PERIOD.

3.  To fix a series of accuracy issues so that the RESNET standard is consistently accurate at within a range of less than 10% instead of the current situation where duct leakage accuracy can be hampered by more than a 35% error.

Proposed Change:

None in this section.


Comment #55

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 1
Paragraph / Figure / Table / Note: 802
Comment Type: Technical

Comment:

802 PROCEDURES FOR BUILDING ENCLOSURE AIRTIGHTNESS TESTING
The purpose of this test procedure is to determine the airtightness of a building enclosure
measured in cubic feet per minute (CFM) at a 50 Pa pressure difference (CFM50).

Justification for Change:

This is needed for the unusual home built in a wind field (on a large lake or sea shore). In that case, Tectite does a much better job estimating infiltration than standard RESNET-approved software which would be very limited if it could only receive as input: CFM50. See the LBL model for infiltration for a full explanation.
 

Proposed Change:

802 PROCEDURES FOR BUILDING ENCLOSURE AIRTIGHTNESS TESTING
The purpose of this test procedure is to determine the airtightness of a building enclosure
measured in cubic feet per minute (CFM) at a 50 Pa pressure difference (CFM50).

However, RESNET approved software will continue to accept ELA as input.


Comment #56

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 1
Paragraph / Figure / Table / Note: 802.1 On-Site Inspection Protocol:
Comment Type: Editorial

Comment:

802.1 On-Site Inspection Protocol:
There are three acceptable airtightness test procedures:
1- Single-point test: Measuring air leakage one time at a single pressure
as described in section 802.5
2- Multi-point test: Measuring air leakage at multiple induced pressures
as described in section 802.6
3- Repeated single-point test: The test is similar to the single point test, but the test is
done multiple times for improved accuracy and uncertainty is estimated using statistics as
described in section 802.7
The building may be tested by applying a positive or negative pressure. Follow all
manufacturers’ instructions for set up and operation of all equipment. If certain
requirements of this standard cannot be met, then all deviations from the standard shall be
recorded and reported.

Justification for Change:

Hyphens are needed to improve the readability of text -- particularly when there are a string of nouns that can be composed in a variety of schemes.

Guessing or hunting for the right associations is a waste of time and may generate differences in interpretation.

Don't give your reader an IQ test.

In future comments of this type, this reason and explanation will be omitted.

Proposed Change:

802.1 On-Site Inspection Protocol:
There are three acceptable airtightness test procedures:
1- Single-point test: Measuring air leakage one time at a single pressure
as described in section 802.5
2- Multi-point test: Measuring air leakage at multiple induced-pressures
as described in section 802.6
3- Repeated single-point test: The test is similar to the single-point test, but the test is
done multiple times for improved accuracy and uncertainty is estimated using statistics as
described in section 802.7
The building may be tested by applying a positive or negative pressure. Follow all
manufacturers’ instructions for set-up and operation of all equipment. If certain
requirements of this standard cannot be met, then all deviations from the standard shall be
recorded and reported.
 


Comment #57

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 -- subsection 3. Crawl spaces
Comment Type: Technical

Comment:

3. Crawlspaces: If conditioned, interior access doors and hatches between the house
and the crawlspace shall be opened and crawlspace exterior access doors, vents
and hatches shall be closed. If unconditioned, interior access doors and hatches
shall be closed. For testing purposes, crawl-space vents shall be open.

Justification for Change:

(The use of "closed" crawl spaces was "coined" by Advanced Energy. They claim that their system cannot be truly modeled as "conditioned" but I'm confident they would not like it opened in a leakiness test. The problem with the use of "closed" is that it mottles the distinction between conditioned and un-conditioned, however, RESNET must clean up this meaning. Perhaps the list of definitions should assert that 1: closed crawl spaces are tested as if they were conditioned and 2: Unvented attics = Conditioned attics = cathedralized attics. Note that the poor choice of words IS our legacy... We must clean these up forthrightly and not expect the novice rater to resolve the apparent inconsistency.) I think it would depend on where the thermal envelope is: if the crawl space perimeter is insulated and the floor above it is not we would want the access open for the test; if the floor is insulated I think not, Advanced Energy's closed crawl space specifications vary between those that are wall-insulated and those that are floor-insulated. In my opinion, a wall-insulated closed crawl space should be NOT be opened during the test, but a floor-insulated, closed, crawl-space should be opened. However, the issue is more interesting than that because in North Carolina the ground is colder than the bottom of the heating comfort zone, however, in New Orleans the ground stays at 72F if unperturbed by weather. This explains why Advanced Energy doesn't classify their wall-insulated closed crawl spaces as conditioned and explains why the same specification in New Orleans should be classified as conditioned!)
 

Proposed Change:

3. Crawlspaces: If conditioned, interior access doors and hatches between the house
and the crawlspace shall be opened and crawlspace exterior access doors, vents
and hatches shall be closed. If unconditioned, interior access doors and hatches
shall be closed. For testing purposes, crawl-space vents shall be open.
 

Closed crawlspaces, i.e., as defined by Advanced Energy will be deemed conditioned if the walls are insulated and the ground temperature stays between 68 and 75 degrees year-round.


Comment #58

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 -- 4. Attics
Comment Type: Technical

Comment:

4. Attics: If conditioned, interior access doors and hatches between the house and
the conditioned attic shall be opened; and attic exterior access doors and windows
shall be closed.

If unconditioned, interior access doors and hatches shall be
closed and exterior access doors, dampers or vents shall be left in their as found
position and their position during testing shall be recorded on the test report.
 

Justification for Change:

Actively conditioned spaces are clearly conditioned.  But the problem comes from passively conditioned spaces.  I think the location of the thermal boundary is more important than the presence of supply or return registers.

Proposed Change:

4. Attics: If conditioned, interior access doors and hatches between the house and
the conditioned attic shall be opened; and attic exterior access doors and windows
shall be closed.

The location of the thermal boundary as opposed to the presence of active supply or return registers defines what is conditioned space.
 

If unconditioned, interior access doors and hatches shall be
closed and exterior access doors, dampers or vents shall be left in their as found
position and their position during testing shall be recorded on the test report.
 


Comment #59

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 5. Interior Doors:
Comment Type: Editorial

Comment:

5. Interior Doors: Shall be open within the Conditioned Space Boundary. See the
definition of “Conditioned Space Boundary” for clarification.

Justification for Change:

(These hyphens are needed to keep the reader from thinking: perhaps you mean Conditioned Space-Boundary.)
 

Proposed Change:

5. Interior Doors: Shall be open within the Conditioned-Space Boundary. See the
definition of “Conditioned-Space Boundary” for clarification.
 


Comment #60

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 5. Interior Doors:
Comment Type: Editorial

Comment:

5. Interior Doors: Shall be open within the Conditioned Space Boundary. See the
definition of “Conditioned Space Boundary” for clarification.

Justification for Change:

(These hyphens are needed to keep the reader from thinking: perhaps you mean Conditioned Space-Boundary.)
 

Proposed Change:

5. Interior Doors: Shall be open within the Conditioned-Space Boundary. See the
definition of “Conditioned-Space Boundary” for clarification.
 


Comment #61

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 6. Suspended grid ceiling:
Comment Type: Technical

Comment:

6. Suspended-grid ceiling: One tile shall be removed to provide pressure relief and
avoid damage by induced pressure differences.

Justification for Change:

The suggestion to also move paper-faced, batt-insulation since without moving it, the movement of a ceiling tile will have little protective effect. However, if there is insulation on the ceiling tile, that surface is the location of the pressure and thermal boundary -- in which case, we have violated the very enclosure we are trying to test! Either way, we're in trouble!. Therefore, I would submit that if we are aware that a 29 Pa pressure across a ceiling tile is sufficient to damage the ceiling, then a ceiling that doubles as the thermal boundary should only be pressure tested below 29 Pa. [I don't know that 29 Pa is the magic value... it was used for rhetorical purposes.] In that case, a blower door test involving a suspended ceiling should never be done at pressures over 25 Pa.
 

Note also the addition of a hyphen in the first noun's adjective.

Proposed Change:

6. Suspended-grid ceiling: One tile and any insulation that covered that tile shall be removed to provide pressure relief and
avoid damage caused by induced-pressures.

However, if insulation is placed upon the ceiling tiles:

I would submit that if we are aware that a 29 Pa pressure across a ceiling tile is sufficient to damage the ceiling, then a ceiling that doubles as the thermal boundary should only be pressure tested below 29 Pa. [I don't know that 29 Pa is the magic value... it was used for rhetorical purposes.] In that case, a blower door test involving a suspended ceiling should never be done at pressures over 25 Pa.  And in this case, no ceiling tiles are moved.
 


Comment #62

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 6. Suspended grid ceiling:
Comment Type: Technical

Comment:

6. Suspended-grid ceiling: One tile shall be removed to provide pressure relief and
avoid damage by induced pressure differences.

Justification for Change:

The suggestion to also move paper-faced, batt-insulation since without moving it, the movement of a ceiling tile will have little protective effect. However, if there is insulation on the ceiling tile, that surface is the location of the pressure and thermal boundary -- in which case, we have violated the very enclosure we are trying to test! Either way, we're in trouble!. Therefore, I would submit that if we are aware that a 29 Pa pressure across a ceiling tile is sufficient to damage the ceiling, then a ceiling that doubles as the thermal boundary should only be pressure tested below 29 Pa. [I don't know that 29 Pa is the magic value... it was used for rhetorical purposes.] In that case, a blower door test involving a suspended ceiling should never be done at pressures over 25 Pa.
 

Note also the addition of a hyphen in the first noun's adjective.

Proposed Change:

6. Suspended-grid ceiling: One tile and any insulation that covered that tile shall be removed to provide pressure relief and
avoid damage caused by induced-pressures.

However, if insulation is placed upon the ceiling tiles:

I would submit that if we are aware that a 29 Pa pressure across a ceiling tile is sufficient to damage the ceiling, then a ceiling that doubles as the thermal boundary should only be pressure tested below 29 Pa. [I don't know that 29 Pa is the magic value... it was used for rhetorical purposes.] In that case, a blower door test involving a suspended ceiling should never be done at pressures over 25 Pa.  And in this case, no ceiling tiles are moved.
 


Comment #63

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 7 Chimney dampers & 8 Combustion
Comment Type: Editorial

Comment:

7. Chimney dampers and combustion air inlets on solid fuel appliances: Shall be
closed. Take precautions to prevent ashes or soot from entering the house during
testing. Although the general intent of this standard is to test the building in its
normal operating condition, it may be necessary to temporarily seal openings to
avoid drawing soot or ashes into the house. Any temporary sealing shall be noted
in the test report.
8. Combustion appliance flue gas vents: Shall be left in their normal appliance-off
condition.
 

Justification for Change:

hyphens help readabiity

Proposed Change:

7. Chimney dampers and combustion-air inlets on solid-fuel appliances: Shall be
closed. Take precautions to prevent ashes or soot from entering the house during
testing. Although the general intent of this standard is to test the building in its
normal operating condition, it may be necessary to temporarily seal openings to
avoid drawing soot or ashes into the house. Any temporary sealing shall be noted
in the test report.
8. Combustion-appliance flue-gas vents: Shall be left in their normal appliance-off
condition.

 


Comment #64

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 9. Fans:
Comment Type: Editorial

Comment:

9. Fans: Any fan or appliance capable of inducing airflow across the building
enclosure shall be turned off including, but not limited to: clothes dryers, attic
fans, kitchen and bathroom exhaust-fans, outdoor-air ventilation fans, air handlers,
and crawl-space and attic ventilation fans. For continuously operating ventilation
systems, turn off the fan and seal the air opening.

 (This step should be mentioned before Steps 7 and 8, namely those on combustion appliances.)
 

Justification for Change:

hyphens improve readability

, changed to :

Add "turn off fan and" which is implied but not clearly stated.

Placing this item from #9 to before #'s 7 & 8 will improve the clarity of the algorithm described within the technical standard.

Proposed Change:

6.5. Fans: Any fan or appliance capable of inducing airflow across the building
enclosure shall be turned off including, but not limited to: clothes dryers, attic
fans, kitchen and bathroom exhaust-fans, outdoor-air ventilation fans, air handlers,
and crawl-space and attic ventilation fans. For continuously operating ventilation
systems, turn off the fan and seal the air opening.

 


Comment #65

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 2
Paragraph / Figure / Table / Note: 802.2 10. Non-motorized dampers
Comment Type: Technical

Comment:

10. Non-motorized dampers which connect the conditioned space to the exterior
or to unconditioned spaces: Dampers shall be left as found. If the damper will
be forced open or closed by the induced test pressure, that fact shall be reported in
the test report.

 

 

Justification for Change:

hyphens improve readability

 

(Should the number and/or total area of such dampers be recorded as well?)

 

Proposed Change:

10. Non-motorized dampers which connect the conditioned space to the exterior
or to unconditioned spaces: Dampers shall be left as found. If the damper will
be forced open or closed by the induced test-pressure, that fact shall be reported in
the test report.

 

The total area to outside of such dampers be recorded as well.


Comment #66

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.2 12. Un-dampered et seq.
Comment Type: Editorial

Comment:

12. Un-dampered or fixed-damper intentional openings between conditioned
space and the exterior or unconditioned spaces: Shall be left open or fixed
position, however, temporary blocking shall be removed. For example: fixed-damper
ducts supplying outdoor air for intermittent ventilation systems (including
central-fan-integrated distribution systems) shall be left in their fixed-damper
position. Exception: Un-dampered supply-air or exhaust-air openings of
continuously operating mechanical ventilation systems shall be sealed (preferably
seal at the exterior of enclosure) and ventilation fans shall be turned off as
specified above.
13. Whole building fan louvers/shutters: Shall be left as found.  If there is a
seasonal cover, install it.
14. Evaporative coolers: The opening to the exterior shall be covered or sealed.
15. Operable-window trickle-vents and through-the-wall vents:

Justification for Change:

hyphens improve readability

Addition of "However, " improves readability.

Proposed Change:

12. Un-dampered or fixed-damper intentional openings between conditioned
space and the exterior or unconditioned spaces: Shall be left open or fixed
position, however, temporary blocking shall be removed. For example: fixed-damper
ducts supplying outdoor air for intermittent-ventilation systems (including
central-fan-integrated distribution systems) shall be left in their fixed-damper
position. Exception: Un-dampered supply-air or exhaust-air openings of
continuously-operating mechanical ventilation systems shall be sealed (preferably
seal at the exterior of enclosure) and ventilation fans shall be turned off as
specified above.
13. Whole-building fan louvers/shutters: Shall be left as found. However, if there is a
seasonal cover, install it.
14. Evaporative coolers: The opening to the exterior shall be covered or sealed.
15. Operable-window trickle-vents and through-the-wall vents:
 


Comment #67

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.2 15. Operable-window et seq.
Comment Type: Editorial

Comment:

15. Operable-window trickle-vents and through-the-wall vents: Shall be closed.

16. Supply registers and return grilles: Shall be left open and uncovered

Justification for Change:

(Remove the BOLD highlighting for all parts of the sentences following the ":".)   Be consistent with such formatting.

Proposed Change:

15. Operable-window trickle-vents and through-the-wall vents: Shall be closed.
 

16. Supply registers and return grilles: Shall be left open and uncovered
 


Comment #68

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.2 17. Plumbing drains
Comment Type: Editorial

Comment:

17. Plumbing drains with p-traps: Shall be sealed or filled with water if empty.

Justification for Change:

addition of a comma just before the conditional clause is grammatically correct and improves readability.

Proposed Change:

17. Plumbing drains with p-traps: Shall be sealed or filled with water, if empty.


Comment #69

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.2 18. Combustion appliances:
Comment Type: Technical

Comment:

18. Combustion appliances: Shall remain off during the test.
For test purposes, if a dryer is not attached, the dryer exhaust opening should not
be sealed off, but this fact should be noted in the test report.
Maintain the above conditions throughout the test. If during the test, induced-
pressures affect operable dampers, seasonal covers, etc. then reestablish the set-up
and consider reversing direction of fan flow.
After testing is complete, return the building to its as found conditions prior to the
test. For example, make sure that any combustion appliance pilots that were on prior
to testing remain lit after testing.

Justification for Change:

Because this step is partially redundant with Step 9, both current step 9 and step 18 should be moved to the beginning of the list and combined or separated into two as desired, but accidental redundancies can cause errors in interpretation and should be avoided, recommend moving to just before step 7.  The careful reader is expected to ask why this is repeated and will look for a reason and may make up something we would not like.
 

Changing "remain" to "be turned off (as needed)" is a change in the wording that anticipates both kinds of initial as found conditions.  In either case, the test should only proceed with the appliance off.

Proposed Change:

6.5. Combustion appliances: Shall be turned off (as needed) during the test.
For test purposes, if a dryer is not attached, the dryer exhaust opening should not
be sealed off, but this fact should be noted in the test report.
Maintain the above conditions throughout the test. If during the test, induced-
pressures affect operable dampers, seasonal covers, etc. then reestablish the set-up
and consider reversing direction of fan flow.
After testing is complete, return the building to its as found conditions prior to the
test. For example, make sure that any combustion appliance pilots that were on prior
to testing remain lit after testing.


Comment #70

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.3 1- Standard level of accuracy
Comment Type: Technical

Comment:

1- Standard level of accuracy- level of accuracy that produces test results that can be used in the modeling software or to assess compliance with a performance standard or program requirement. This is the level of accuracy that is normally attained unless there are adverse testing conditions such of high winds or very large pressure adjustments.

Justification for Change:

There is one, minor, editorial comment about changing a hyphen to a comma. Using a hyphen to begin a definition is a dangerous way to convey meaning. I prefer a comma for that purpose.

However the main concern here is more technical: Poor accuracy in a blower-door test may also be exaccerbated by a very-leaky building. For example, if one cannot reach 5 Pa with the fan fully on, the error of assigning that flow to 4.00 Pa can be greater than the error associated with wind effects.

Moreover, we are talking about ascertaining the quality of accuracy. Our algorithm begins with measuring a baseline. So that is what we should be referring to at this point.

Proposed Change:

1- Standard level of accuracy: level of accuracy that produces test results that can be used in the modeling software or to assess compliance with a performance standard or program requirement. This is the level of accuracy that is normally attained unless there are adverse testing conditions such as some combination of high winds, an extremely leaky building or very-large, baseline-pressure adjustments.


Comment #71

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3
Paragraph / Figure / Table / Note: 802.3 2- Reduced level of accuracy:
Comment Type: Editorial

Comment:

2- Reduced level of accuracy- during adverse testing conditions or in certain
applications where testing time and costs are a factor, a test with a reduced level
of accuracy may be used. Such applications may include demonstrating
compliance with a performance threshold or a specific program requirement.
Measurements made with a reduced level of accuracy may require surpassing the
threshold value by an amount which will account for the added uncertainty as
defined in the sections below. Accredited software that uses test results
with a reduced level of accuracy shall internally adjust the calculations in
accordance with this chapter.
 

Justification for Change:

editorial suggestions to improve readability.

Clarifying suggestion at the end of the 2nd sentence tells the reader where to find the list of situations that lead to a reduced level of accuracy test.

RESNET-accredited is stronger than accredited.

Proposed Change:

2- Reduced level of accuracy: during adverse testing conditions or in certain
situations where testing time and costs are a factor, a test with a reduced level
of accuracy may be used. Such situations may include demonstrating
compliance with a performance threshold or a specific program requirement; a complete list of the applicability of a reduced level of accuracy is provided in 802.8.1.
Measurements made with a reduced level of accuracy may require surpassing the
threshold value by an amount which will account for the added uncertainty as
defined in the sections below. RESNET-accredited software that accepts test results
with a reduced level of accuracy shall internally adjust the calculations in
accordance with this chapter.

 


Comment #72

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3 et seq
Paragraph / Figure / Table / Note: 802.4
Comment Type: Editorial

Comment:

802.4 Installation of the blower door airtightness testing system:
1. Install the blower door system in an exterior doorway or window that has
unrestricted access to the building and no obstructions to airflow
 

Justification for Change:

hyphens improve readability

Proposed Change:

802.4 Installation of the blower-door airtightness testing system:
1. Install the blower-door system in an exterior doorway or window that has
unrestricted access to the building and no obstructions to airflow

 


Comment #73

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 3 et seq
Paragraph / Figure / Table / Note: 802.4
Comment Type: Editorial

Comment:

802.4 Installation of the blower door airtightness testing system:
1. Install the blower door system in an exterior doorway or window that has
unrestricted access to the building and no obstructions to airflow
 

Justification for Change:

hyphens improve readability

Proposed Change:

802.4 Installation of the blower-door airtightness testing system:
1. Install the blower-door system in an exterior doorway or window that has
unrestricted access to the building and no obstructions to airflow

 


Comment #74

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4
Paragraph / Figure / Table / Note: 802.4 part 1
Comment Type: Technical

Comment:

1. Install the blower-door system in an exterior doorway or window that has
unrestricted access to the building and no obstructions to airflow within five feet of
the fan inlet. Avoid installing the system in a doorway or window exposed to the wind.
 

Justification for Change:

Airflow clearance on both sides of the fan should be required since :

1.  restriction on either side should affect the laminar flow at the sampling point used to induce flow from pressure.

2. during a duct-blaster test, the fan is often reversed in direction.

Proposed Change:

1. Install the blower-door system in an exterior doorway or window that has
unrestricted access to the building and no obstructions to airflow within five feet of
the fan inlet on both sides of the fan. Avoid installing the system in a doorway or window exposed to the wind.

 


Comment #75

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4
Paragraph / Figure / Table / Note: 802.4 part 1 a
Comment Type: Technical

Comment:

a. It is permissible to use a doorway or window between the conditioned space
and unconditioned space as long as the unconditioned space has an
unrestricted pathway to the outdoors. For example, an attached garage or
porch can be used as the unconditioned space; in that case, be sure to open all
exterior windows and doors of the unconditioned space to the outdoors.
 

Justification for Change:

Without the suggested improvements in the standard algorithm, there will be no clear way of determining what constitutes "unrestricted pathway to the outdoors".  Even these recommendations may not be adequate, but I think they are.

Proposed Change:

a. It is permissible to use a doorway or window between the conditioned space
and a well-vented to outside, unconditioned space as long as the unconditioned space has an
unrestricted air-pathway to the outdoors which is much larger than the orifice of the blower door. For example, an attached garage or
porch can be used as the unconditioned space; in that case, be sure to open all
exterior windows and doors of the unconditioned space to the outdoors; but in no case can the total area of these openings be less than 20 sq ft.
 


Comment #76

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4
Paragraph / Figure / Table / Note: 802.5 section 1
Comment Type: Technical

Comment:

1. Choose and record a time-averaging period of at least 10 seconds - to be used
for measuring pressures: With the blower door fan sealed and off, measure an average baseline pressure reading with
respect to outside to a resolution of 0.1 Pa.
 

Justification for Change:

The reasons for this substantial rewrite include: 1) time-averaging period is redundant because "period" implicitly means "time-period" while test-averaging period is what is meant; it is the test that is averaged, not the time. 2) without using the phrase "time-interval" in the first sentence, it is not clear what the rater gets to "choose". 3) The final clause of the 1st sentence merely defines the name of the choice -- instead of asking the rater to make a choice for a term he does not understand. The definition terminology is parallel in style to a similar clause in the step numbered "4" below. 4) The first clause had ended in a "colon", but now it ends in a period to clarify that the choice of test-averaging period is independent from the repetition of the baseline test. 5) The second sentence should start with "Using this test-averaging period" because, if left out, the rater may wonder what was the use of the previous sentence. Leave no doubt in meaning! 6) The word "independent" should be deleted because the rater has no way of assuring or even understanding that the following repetitions will be independent. In fact, they will be dependent upon shared testing conditions and errors in setup. 7) By splitting the final sentence of this section into two sentences, it is easiest for the rater to understand what is done during each averaged baseline test and what accuracy to record; in the previous version the attempt to say everything in one sentence left hanging or confusing assumptions/interpretations about what was recorded and what was repeated.

 

Proposed Change:

1. Choose and record a time interval of at least 10 seconds -- to be used
for measuring average baseline pressures; this time-interval is defined as the test-averaging period. Using this test-averaging period, with the blower-door fan sealed and off, measure an averaged baseline building-pressure reading with
respect to outside and
record the reading to a resolution of 0.1 Pa. Repeat this test a total of five times.

 


Comment #77

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4
Paragraph / Figure / Table / Note: 802.5 section 2
Comment Type: Technical

Comment:

2. Subtract the smallest baseline measurement from the largest recorded in Step 1
and record this as the baseline range.

Justification for Change:

Explaning that subtraction with negative numbers is exactly what is meant.

Proposed Change:

2. Subtract the smallest baseline measurement from the largest recorded in Step 1
and record this as the baseline range. For example: note that the -3 Pa is less than 2 Pa and - 3 Pa subtracted from 2 Pa is 5 Pa.
 


Comment #78

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4
Paragraph / Figure / Table / Note: 805.2
Comment Type: Editorial

Comment:

3. Airtightness tests with a baseline range less than 5.0 Pa, will be considered a
Standard Level of Accuracy Test. Airtightness tests with a baseline range
between 5.0 Pa and 10.0 Pa will be considered a Reduced Level of Accuracy
Test and the results will be adjusted using Section 802.8. A one point test
cannot be performed under this standard if the baseline range is greater than
10.0 Pa. Record the level of accuracy for the test as standard or reduced, as
appropriate. The baseline test may be repeated employing a longer time
averaging period in order to meet the desired level of accuracy.

Justification for Change:

"Interpretation and use of the" is clearer than "using".

Hyphen added to improve readability.

The baseline test "and its interpretation, i.e., steps 1-3" etc is clarifying.

Use of alternative and better name for time-averaging period to test-averaging period.

Proposed Change:

3. Airtightness tests with a baseline range less than 5.0 Pa, will be considered a
Standard Level of Accuracy test. Airtightness tests with a baseline range
between 5.0 Pa and 10.0 Pa will be considered a Reduced Level of Accuracy
test and the interpretation and use of the results will be adjusted according to Section 802.8. A one-point test
cannot be performed under this standard if the baseline range is greater than
10.0 Pa. Record the level of accuracy for the test as standard or reduced, as
appropriate. The baseline test and its interpretation, i.e., steps 1 - 3, may be repeated by employing a longer, test-averaging period in order to improve the desired level of accuracy.

 


Comment #79

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4
Paragraph / Figure / Table / Note: 802.5 section 4
Comment Type: Technical

Comment:

4. Re-measure the baseline building pressure using the same time averaging
period recorded in Step 1. This measurement is defined as the Pre-Test
Baseline Building Pressure. If desired for greater accuracy, a longer time
averaging period may be used. As an alternative, the median value of the 5
average baseline building pressure readings taken in Step 1 may be used in lieu
of re-measuring the baseline building pressure. Record the Pre-Test Baseline
Building Pressure.

Justification for Change:

(Why bother even mentioning "re-measuring"? this is both a waste of time and a loss in accuracy. No one will do it; why should they? There is no need to mention repeating steps 1 - 3 for greater accuracy; this was already stated in the last sentence of Step 3.)
 

Proposed Change:

4. The median value of the 5,
averaged baseline building-pressure readings taken in Step 1 is defined as the Pre-Test Baseline
Building-Pressure.


Comment #80

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 4 et seq
Paragraph / Figure / Table / Note: 802.5 section 5
Comment Type: Technical

Comment:

5. Unseal the blower door fan. Turn on and adjust the fan to create an induced
building pressure of approximately 50 Pa. Induced building pressure shall be defined as the (unadjusted) building pressure minus the pre-test baseline
building pressure. If a 50 Pa induced building pressure cannot be achieved
because the blower door fan does not have sufficient flow capacity, then
achieve the highest induced building pressure possible with the equipment
available.

Justification for Change:

hyphens added.  5x

Target pressure must be 50Pa higher than baseline.  If the baseline is near 4Pa then the target pressure should be 54Pa.

Not having sufficient flow capacity only makes sense in the case of a particularly leaky house.  Why not state this instead of making the rater figure this out?

Proposed Change:

5. Unseal the blower-door fan. Turn on and adjust the fan to create an induced
building-pressure of about 50 Pa higher than the pre-test baseline building-pressure. Induced building-pressure shall be
defined as the (unadjusted) building-pressure minus the pre-test baseline
building-pressure. If a 50 Pa, induced building-pressure cannot be achieved
because the blower-door fan does not have sufficient flow capacity to meet the leakiness of the building up to 50 Pa, then
achieve the highest induced building-pressure possible with the equipment
available.
 


Comment #81

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: 802.5 section 6
Comment Type: Technical

Comment:

6. A one-point test may only be performed if the maximum induced building
pressure is at least 15 Pa or four times the baseline pressure, whichever is
larger. If the maximum induced building pressure is less than 15 Pa, recheck
that the house set up is correct and determine if any basic repairs are needed
prior to further testing or modeling of the building. A multi-point test may be
attempted, or multiple fans may be used. If using multiple fans, follow the
manufacturer’s instruction for measurement procedures.

Justification for Change:

hyphens added.

 

"and greater than" four times is better than "or four times".  What was there allowed for choice.  Not all people see "OR" as inclusive.  There is no need for choice here anyway.

Removed a comma as well.

Proposed Change:

6. A one-point test may only be performed if the maximum induced building-
pressure is at least 15 Pa and greater than four times the baseline pressure. If the maximum induced building-pressure is less than 15 Pa, recheck
that the house set-up is correct and determine if any basic repairs are needed
prior to further testing or modeling of the building. A multi-point test may be
attempted or multiple fans may be used. If using multiple fans, follow the
manufacturer’s instruction for measurement procedures.
 


Comment #82

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: 802.5 section 7
Comment Type: Editorial

Comment:

7. Measure and record the unadjusted building pressure and nominal (not
temperature and altitude corrected) fan flow using the same averaging period
used in Step 4. Record the unadjusted building pressure (with 0.1 Pa
resolution), nominal fan flow (with 1 CFM resolution), fan configuration
(rings, pressurization or depressurization, etc), fan model and fan serial
number.
 

Justification for Change:

hyphens.

"Using an induced building-pressure in accordance with steps 5 and 6,"  is clearer than what was there.

Proposed Change:

7. Using an induced building-pressure in accordance with steps 5 and 6, measure and record the unadjusted building-pressure and nominal (neither
temperature- nor altitude-corrected) fan flow using the same test-averaging period
last chosen in Step 1. Record the unadjusted building-pressure (with 0.1 Pa
resolution), nominal fan flow (with 1 CFM resolution), fan configuration
(rings, pressurization or depressurization, etc), fan model and fan serial
number.
 


Comment #83

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 5
Paragraph / Figure / Table / Note: 802.5 section 9
Comment Type: Technical

Comment:

9. If your pressure gauge has the capability to display the induced building
pressure (i.e. “baseline adjustment” feature) and adjust the fan flow value to an
induced building pressure of 50 Pa (i.e. “@50 Pa” feature), then follow the
manometer manufacturer’s procedures for calculating the results of a one-point
test and record the following values: induced building pressure, nominal
CFM50, fan configuration, fan model and fan serial number. If needed
Calculate the following values:
?? induced building pressure =
measured building pressure minus the Pre-Test Baseline
Building Pressure
Note: If a “baseline adjustment” feature of the manometer was used,
then the induced building pressure is displayed on the pressure
gauge.
?? nominal CFM50 = (50 / induced building pressure) 0.65 x recorded fan
flow
Note: If both a “baseline adjustment” feature and an “@50 Pa”
feature were used, the nominal CFM50 is displayed directly on the
pressure gauge.
If the altitude is above 5,000 feet or the difference between the inside and
outside temperature is more than 30 degrees Fahrenheit then calculate the
corrected CFM50 as defined below:
?? corrected CFM50 =

nominal CFM50 x altitude correction factor x temperature
correction factor
where
altitude correction factor = 1 + .000006 x altitude,
altitude is in feet
temperature correction factors
are listed in Table 802.10
?? ACH50 = corrected CFM50 x 60 / building volume (in cubic feet).
(This calculation may be omitted if the ACH50 metric is not
needed.)

Justification for Change:

hyphens...

Note that in the worst case scenario, a home tested at 15 Pa with a 5 Pa baseline range has an RESNET-accepted accuracy (i.e., applicability) identical to a home tested at 50 Pa with a 1 Pa baseline range. This is a gross difference in the error estimate of CFM50 that is ignored! What are you proposing to do about it? Although, for some practical purposes we can agree to live with that error, later asserting that another test is not accurate enough seems ludicrous! This is especially significant since computer-controlled multi-point blower-door envelope-leakage tests, like that provided by Tectite-controlled APT or DG7000 can provide order of magnitudes more accurate CFM50. In response to David's question: I have no problem and in fact I applaud the Technical Committee's decision to set a threshold of accuracy for "Standard Accuracy". The reason I'm making this parenthetical comment is to point out that "Standard Accuracy" for a building envelope leakage test is well defined as 10% of CFM50 at 95% confidence, but no such issue is forthrightly addressed regarding "standard accuracy" for a duct leakage test. This issue is joined for me because of the inconsistent remarks I quote later and most significantly their effect: the omission of a quality contender for duct leakage testing: GSCA.

For this reason and reasons provided later in my comments, I am submitting the section numbered 803.10 in order to remediate this problem and those I will refer to later.

Proposed Change:

9. If your pressure gauge has the capability to display the induced building-
pressure (i.e. “baseline adjustment” feature) and adjust the fan flow value to an
induced building-pressure of 50 Pa (i.e. “@50 Pa” feature), then follow the
manometer manufacturer’s procedures for calculating the results of a one-point
test and record the following values: induced building-pressure, nominal
CFM50, fan configuration, fan model and fan serial number. Otherwise, as needed,
Calculate the following values:
?? induced building-pressure =
measured building-pressure minus the Pre-Test Baseline
Building Pressure
Note: If a “baseline adjustment” feature of the manometer was used,
then the induced building-pressure is displayed on the pressure
gauge.
?? nominal CFM50 = (50 / induced building pressure) 0.65 x recorded fan
flow
Note: If both a “baseline adjustment” feature and an “@50 Pa”
feature were used, the nominal CFM50 is displayed directly on the
pressure gauge.

 

803.10 Generalized Subtraction Correction Algorithm (GSCA) for Duct Leakage-to-Outside testing. (Submitted by Myron Katz of Building Science Innovators, LLC)

The purpose of this test procedure is to determine duct leakage-to-outside of the conditioned space.

(Much if not most of the following content in this discourse, particularly until the beginning of section 803.10.1, finds its way into this document in order to require its careful review by the RESNET technical committee and RESNET Board according to ANSI standards on creating a standard. However, that is not to say that the authors of 803.10 believe that all this explanatory argumentation belongs in the final version of the published standard.)

This test is not intended to supplant the RESNET-Standard duct leakage-to-outside test described in 803.2 - 803.7 but, instead, to provide an alternative RESNET-approved standard that can be used when applicable. In many, if not most cases, when the current RESNET standard is applicable, GSCA can also be used, thereby providing many additional benefits.

GSCA cannot be used to measure Total Duct Leakage. Neither can GSCA be used to measure Duct Leakage-to-outside when parts of the duct system are located in more than one outside-of-the-thermal-envelope volumes like the crawl space and attic, multiple attics, or an attic and garage, etc. Neither can GSCA be used if there is more than one duct system. Moreover, like most of the other proposed, RESNET-approved, duct-leakage-testing protocols, GSCA does not separate supply from return duct leakage and GSCA does not measure the actual duct leakage while the HVAC system is running. It has a few other, but rarely found in practice, limitations as well; for example, GSCA expects a small drop in the duct-envelope-volume pressure when comparing the taped case to the untaped case: if this drop is greater than 1 Pa, problems of GSCA applicability occur. See the referenced engineering article at the end of this section for more details.

However, GSCA has much to recommend it:
1. GSCA requires less testing equipment. No duct-fan-pressurization tester is needed. However, for optimal accuracy, a fully-automated, data-collection system must be used. This typically includes two or three machines: 1) a laptop computer and 2) two DG700's or a four-manometer APT or equivalent. (There is a way to do this test without significant loss of accuracy with only two machines, i.e., only one DG700, but that will be left to the clever reader-experimenter to discover.) In the near future, the needed laptop computer may be replaced by a suitably-adapted, "smart" cell phone. However, these authors do not know of a case where a cell phone has been used to control a DG700 or similar manometer. (Check with one of the blower-door manufacturers for an recent update on this issue.) A non-scientific survey at the last two RESNET conferences suggest that about half of all raters already bring a laptop computer and a DG700 or equivalent to most jobs and almost as many already do multi-point, building-envelope-leakage testing.
2. GSCA requires less on-site rater time. GSCA can be performed while the rater is performing other tasks. Since the test is fully automated, the setup is the only time-consuming part. Most of the GSCA setup is already required for normal, blower-door testing anyway. Thus ... not much additional work is required. In fact, the extra work that is required is substantially less time-consuming than that required to merely setup a duct fan pressurization test.
3. GSCA has higher accuracy. As explained in the parenthetical notes within draft sections 803.2-7, the difference between two highly accurate automated multi-point tests should have an expected error substantially lower than the current RESNET-proposed, draft, duct-leakage-to-outside standard.
4. A paper trail is generated on all data collections and calculations. This trail improves the ability for the Quality Assurance Designee to confirm that building-envelope and duct-leakage testing was done correctly. Consequently, the large scale application of GSCA has the potential to increase the accuracy of both building and duct leakage testing for an even larger percentage of the industry.
5. GSCA facilitates ZPD. The data collection process of GSCA requires half or more of the data collections needed for Zone-Pressure Diagnostics (ZPD) and 90% of the setup ... thereby facilitating and directing weatherization programs and energy audits. This is particularly the case since moving the thermal boundary is the paramount first step to optimal energy auditing and ZPD is needed to optimally estimate the energy savings garnered by avoided infiltration resulting from the movement of the thermal boundary. GSCA requires the pressure monitoring of at least one non-conditioned volume within the building during an 8-point pressure test. This exposes the rater to observations that will enhance understanding of infiltration dynamics of that building. (The concept of an attic to house pressure-coupling ratio is an example of this.)
6. GSCA exposes errors in setup in real-time. The largest percentage of errors in setup is found when the rater sees in real-time both the non-linearity of the data collected as graphed on a log-log scale and the fluctuations and size of data recorded during baseline pressure testing. GSCA allows the rater to correct the setup errors before completing the first building envelope leakage test, any duct leakage test, dismantling the setup or leaving the job-site. Such errors are often never found, but when they are suspected hours to days later, much time and money are wasted.
7. GSCA requires less invasive, less time-consuming and less potentially equipment damaging setup. In particular, the filters of the duct system do not need to be removed. Neither do zone or bypass (not balancing) dampers need to be set to the open position to facilitate uniform pressures throughout the duct system.
8. GSCA can be fully automated by hardware manufacturers.
9. GSCA requires a full set of pressure-pan tests as part of the setup. This has the dual value of improving the accuracy and repeatability of GSCA and providing access to the pressure-pan data for more insight into where to concentrate duct-leakage-repair work.
10. With GSCA, duct-leakage testing is more integrated into building-envelope-leakage testing and zone-pressure diagnostics in a way that is optimally computer friendly and provided with real-time help to guide the rater to fix errors in setup. Thus GSCA provides a bridge to a platform for a fully-integrated, whole-building approach to more error-free data-collection to support auditing and weatherization.

Define the Duct Envelope Volume as the part of building that contains all of the duct system that is outside of conditioned space. In many homes this is the attic. For other buildings, it may be the garage, crawl space, or basement, etc. GSCA is not applicable if the duct system that is outside of conditioned space is located in a more than one combination of the above, or if the duct system is part of a package unit, where, for example, part of the HVAC unit is outside, part of the unit is in an attic or crawl space and the rest is in conditioned space; in these latter cases, the duct envelope volume is undefined.

GSCA purports to measure duct-leakage-to-outside when the pressure between the ducts and the duct envelope volume is 25 Pa. Unlike the alternative RESNET-standard, duct leakage-to-outside test, GSCA does not ignore changes in the duct-envelope-volume pressure.

To best appreciate, exploit and understand this concept, GSCA defines three terms:

PD = the pressure difference between the duct system and the duct envelope volume
for arbitrary induced building-pressure.

PD25 = the pressure difference between the duct system and the duct envelope volume when the induced building-pressure is 25 Pa.

P* = the induced building-pressure
when PD = 25 Pa.

Heretofore, any duct leakage test done at 25 Pa will actually measure flow at a pressure of PD25 even though PD25 is probably (and possibly significantly) less than 25 Pa. What is needed is a test of duct leakage where the equipment is set to run at P* in order to assure that is PD in fact 25 Pa. GSCA solves this problem and it does it without requiring extra data collections or opening doors that cannot be opened or cannot be easily opened.

Hereinafter, the ' or apostrophe placed after a pressure, coefficient, exponent or flow symbol refers to the taped case and the lack an apostrophe indicates the untaped case. I.e., Q = C x Pn is the flow equation for the untaped case and Q' = C' x Pn' is the flow equation for the taped case. Similarly, P'D corresponds to the pressure difference between the duct system and the duct envelope volume during a taped test.

When performing a GSCA, (duct-leakage-to-outside test,) a blower door is used to perform a pair of multi-point, building-envelope-leakage tests each as described in 802.6, but each are performed in a fully-automated fashion. However, to facilitate all data collections needed for GSCA, a few extra setup steps are required before the first, multi-point test is performed.

GSCA evolved from the Subtraction Method, and its daughter, Modified Subtraction. (Until c2000 or few years thereafter, Modified Subtraction was the only RESNET- approved duct-leakage-to-outside testing protocol.) Subtraction Method is based on the assumption that in the first approximation, duct-leakage-to-outside is the difference between two blower-door tests where the first is performed with ducts in their normal, untaped condition and the second blower door test is performed with the ducts masked or taped. Modified Subtraction utilizes a subtraction-correction factor to improve the Subtraction Method to accommodate the error arising from duct-leakage flows to inside that were undermining its accuracy; the subtraction-correction factor is calculated from a measured change in duct pressure during the two tests. GSCA improves upon Modified Subtraction by collecting the same data, and in addition, measuring pressure changes in the Duct Envelope Volume -- a pressure that is not always the same pressure as outside when the building is depressurized to 50 Pa. Although during the initial setup for the two building envelope tests needed for a GSCA calculation--one cannot know a priori which induced building-envelope pressure corresponds to a 25 Pa pressure-difference between the duct system and the duct envelope volume in the untaped case, that information is not needed at the beginning of the test to assure that this measurement is available when the test is over. That is, even though P* is not known in advance, we can still calculate the difference in flows at this pressure a posteriori, because the automated, multi-point-test controlling software outputs the parameters of the flow equation, Q = C x Pn, namely, the software reports the flow coefficient and flow exponent for each building-envelope-leakage test. Since measured pressure is homogeneously proportional to input pressure for all the duct pressure and duct envelope volume pressure data collected, we know that P* = 25 x (25 / PD25); thus P* can be input into both flow equations to calculate Q - Q' at the appropriate input pressure. However, to provide data of adequate accuracy, heretofore, all versions of blower-door subtraction had a fundamental fatal flaw: the desired duct leakage-to-outside to be calculated is often smaller than the error in the measurements of each of the two building-envelope-leakage measurements. To overcome this problem, GSCA is only recommended wherein the data is collected with automated performance testing equipment controlled by software, and even in these cases, the building envelope tests must be sufficiently precise to reliably obtain expected errors in CFM50 of less than 0.5% at a 95% confidence level. (At this writing, the author is not sure that this level of accuracy is needed, but it is easily available and will generate calculated duct leakage-to-outside measurement that will be reliably more accurate than competing, standard tests.) In that case, the two, building-envelope-leakage measurements can be made with sufficient accuracy that their difference has an expected error smaller than what the RESNET technical committee considers insignificant in its current duct-leakage-to-outside standard. The mathematical derivation of GSCA can be found in ASTM's Journal on Testing and Evaluation, November 2004, Volume 23, Number 6 or from its authors upon request.

803.10.1 GSCA Simplified-Test-Procedures:

For purposes of this chapter, duct leakage may be measured by either pressurizing or
depressurizing the building and duct system in two nearly consecutive blower-door tests; the first test is only slightly different from 802.6; the second test is exactly the same as the first test except it is performed after supply and return grilles are temporarily sealed in a manner that permits the separation of the duct system from the building at these standard duct system openings. Both building envelope leakage tests are fully-automated, multi-point tests performed with software that that controls the computer's data collections.

Two additional pressures are recorded multiple times at target induced-pressures:
a) The pressure in a sample supply or return register that is masked off for both the taped and untaped tests, and
b) The pressure in the duct envelope volume.

From these data, all of the benefits of GSCA can be harvested.

803.10.2 GSCA Detailed-Test-Procedures:

The following describes the test with depressurization, but GSCA can be performed equally well, and easily, with pressurization. Depressurization is usually preferred because it naturally closes most of the commonly-found, exhaust-vent dampers. It should also be noted that most of the testing work performed to setup for GSCA is already needed for otherwise-required, building-envelope-leakage testing.

803.10.2.1 GSCA Setup Procedures:

1. Setup the equipment but not the software for a multi-point building-envelope-leakage test as described in 802.6, but prepare hardware for a software-controlled computer to control the blower-door fan-speed and all data collections via a smart, dual or multi-channel manometer (similar to a DG700 or APT). Notice that this approach exceeds the 802.6 specifications since this system can perform all required multi-point data collections for a building-envelope-leakage test in a fully-automated fashion.
2. Perform a complete set of pressure-pan tests.
A) Let the software test the blower door against the building's leakiness following a one minute, baseline-monitoring-averaging measurement. Set the software to cruise the blower door at 50 Pa or the highest pressure below 50 Pa it can reach. Define H to be 60 Pa or the highest induced building-pressure below 60 Pa that can be reached by the blower door.
B) Assemble the pressure-pan system: connect a digital pressure gauge by a tube to a pressure pan that is attached to a pole to allow the rater to position the pressure pan over each supply or return grille in a fashion to significantly mask it and allow the rater to read the manometer.
C) Partially mask all supply and return grilles as needed to leave a hole of at least one sq ft or more but having a size and shape not to exceed the footprint of the pressure pan.
D) Name and list the names of each supply and return register in an electronic record. (Although this step can be done with paper, all of the rest of the data collections are electronic; therefore for a variety of goals including Quality Assurance, the plan is that this data is collected and stored via spreadsheet software like Excel.)
E) One by one, visit each supply and return grille, temporarily completely cover the unmasked opening in the grille with the pressure pan and read the pressure across that grille with respect to inside.
F) Record each datum adjacent to the appropriate grille's name. Also record the cruise pressure that was used for all the tests. For quality-assurance repeatability, specify which exterior door or window was used for the location of the blower door.
3. Choose the supply or return grille that is closest to the blower door, but more importantly, is closest to the pressure that is the average pressure found in all pressure-pan tests. This grille is defined to be the Sample Register.
4. Mask the sample register and place a pressure-sampling probe a few inches through the mask. Run the other end of this tube to the vicinity of the computer.
5. Run a tube into the duct enclosure volume; run the other end of this tube to the vicinity of the computer.
6. Using either a four-manometer or two dual manometers or equivalent equipment, connect all hardware and tubes via the manometers to the computer in a fashion so that four pressures can be simultaneously read and stored by the software. Two of these manometers should already be connected to outside and the blower door fan, since this was required in Step 1 above. The other two manometers receive the tubes coming from the sample register and the duct enclosure volume; both will be measured relative to inside pressure.

803.10.2.2 GSCA Testing Procedures:

1. Complete the setup of the software to perform the multi-point test to completely conform to 802.6 in a precisely repeatable fashion. This step exceeds Step 1 in section 803.10.2.1 and is only possible after Step 2 established, H, the highest possible, induced building-pressure. Set the software to use 8, equally-spaced, target induced building-pressures for data collections ranging from H down to 15 Pa, if possible. However, to optimize the accuracy and repeatability of the calculation of CFM50, choose the target pressures exactly as follows:
If H > 30 Pa, use G = (H - 15) / 7
If 20 < H < 30 Pa, use G = (H - 10) / 7.
If 15 < H < 20 Pa, use G = (H - 8) / 7.
If 11 < H < 15 Pa, use G = (H - 6) / 7.
If 8 < H < 11 Pa, use G = 1/2.
Choose the target building-pressure to be the greatest integer < :
H, H-G, H-2G, H-2G, H-4G, H-5G, H-6G, H-7G.

For example, if H were 35, then G = (35-15)/7 ~= 2.86 and the target pressures are:
35, 32, 29, 26, 23, 20, 17, 15.

For example, if H were 10, then G = 1/2 and the target pressures are:
10, 9, 9, 8, 8, 7, 7, 6

If H is less than 8 do not use GSCA. In fact, in practice, it may not be feasible to try to get such highly accurate CFM50 if H is less than 15 Pa. But with a really windless day, and/or by using a 2-minute test averaging period, such accuracy can often be reached, nonetheless. Input inside and outside temperatures and altitude data as the software requests. (Input into Tectite stack-effect and wind-shielding approximations as well. Although these last two are not needed for GSCA, they provide access to ELA which for some homes should be the preferred means for inputting parameters of building-leakiness into RESNET-approved energy rating software.)

2. Setup the software to record and report statistical data for the sample-register pressure and the duct-envelope-volume pressure for every data point collected above.
3. Run the automated, multi-point, building-envelope-leakage test by clicking the "start test" button in the software; change flow rings as needed.
4. Watch the data collection and look for and correct errors in setup.
A) Observe the real-time measurement of the pre-test baseline data to check for setup errors. (Are the values what you expect? Possible causes are running the attic fan. stack-effects (causing a negative pressure) a wind effect (causing fluctuations in the baseline readings)).
B) Observe the slowly forming, log-log graph of the collected (pressure, flow) data points to check the co-linearity of the data. If they are far from linear, stop the test and fix the setup errors before restarting the testing.
C) When the first test is complete, name and save the test. Notice the calculated error in CFM50 as well as the calculated correlation coefficient of the input data. Are they acceptable or do you need to repair the setup?
D) If needed, repair all errors in data collection and repeat the test. Consider that as the sun moves in the sky, stack effect and the effects of wind usually change.
E) Experience indicates that a correlation coefficient less than 0.99 is a poor result that can be repaired with slight improvements in the setup of the equipment. Correlation coefficients greater than 0.999 will happen very often if the rater is careful; these are very good results. However, if the baseline measurement is too large or H is too small, the rater will never get a very low expected error in CFM50 -- no matter how high the correlation coefficient.
5. After the rater has gained experience from performing this test in 10 homes, the rater will realize what accuracy can be expected after the first two tests at the next home. There is little payoff to try to improve testing when CFM50 has an error estimate below 0.5%. On the other hand, if the error estimate of CFM50 cannot be made better than 5% do not expect very good GSCA accuracy.
6. The rater should now have two (2) or more test result files for the duct grilles' untaped case.
7. Tape all duct grilles.
8. Repeat the automated test using the setup conditions of the most successful untaped case. Save the test and repeat.

803.10.2.2 GSCA Calculation Procedures:

1. Chose the most accurate untaped test and the most accurate taped test and input their data to the Duct Leakage Calculator, Excel file. (A version of it should accompany this document. The ELA datum requested within it is not used for GSCA.)
2. Duct leakage to outside at 25 Pa denoted by DLO25 is calculated by:

DLO25 = Difference x Duct Factor x Duct Envelope Volume Factor †

DLO25 = (Q – Q’) x (PD0.6/[PD0.6 – P’D0.6]) x (25/PD25)(n + n')/2

where ’ denotes taped and

Difference is Q – Q’ for P = 25 Pa, where Q = C x Pn

Both C and n have been stored by the software for both the taped and untaped cases.

Q – Q’ = C x 25n - C' x 25n'
(This flow factor is the first order subtraction, evaluated at 25 Pa.)

Duct Factor = PD250.6 / [PD250.6 – P’D250.6]
(This is a generalized version of the subtraction-correction factor.)

Duct Envelope Volume Factor = (25 / PD25) (n + n')/2
(This is new factor displays the effect of a change in duct-envelope-volume pressure.)


† (In fact, the most accurate way to calculate GSCA's DLO25 uses the following formula:

DLO25 = Difference|(P*) x Duct Envelope Volume Factor

DLO25 = (Q – Q’)|(P*) x (PD250.6/[PD250.6 – P’D250.6])
where
(Q – Q’)|(P*) = C x (P*)n - C' x (P*)n' for P* = 25 x ( 25 / PD25)
= C x (25x25/PD25)n - C' x (25x25/PD25)n'
{This formula for P* is found just after equation 20 in the ASTM paper.}

However, for very small differences between n and n',
(Q – Q’)|(P*) is negligibly different from
(C x (25)n - C' x (25)n' ) x (25/ PD25)(n + n')/2 i.e., the first formula.

The first formula for GSCA calculation of DLO25 was presented initially and used in the freely distributable, GSCA duct leakage calculator for two reasons.
i) The first formula better facilitates understanding regarding the direct effect of the change in duct-envelope-volume pressure on the calculated duct-leakage-to-outside result because it is a separate factor.
ii) The down-side of this conceptually-clarifying formula is a very small error: it's use generates an error in the result on the order of 0.3% when changes in the flow exponent from untaped to taped are on the order of 0.01 -- a change in n that should not be expected to be exceeded. Thus the duct leakage calculator uses the first formula presented herein to present a slightly less accurate but much more explanatory calculation method than what the most accurate GSCA system should use.
For optimal accuracy, this second formula should be implemented in any fully-automated version of GSCA even though the first formula belongs in the freely distributable, GSCA-DuctLeakageCalculator.xls.)

Sample Calculation:

This is a sample calculation with the attic is the duct envelope volume.

Results from an untaped test home depressurized to 50 Pa :
Flow formula for untaped is Q = 210 * P 0.65,
Attic pressure is 30 Pa and Sample-register pressure is 3 Pa.

Results from the same home with ducts taped and depressurized to 50 Pa:
Flow formula for taped is Q = 202 * P 0.66,
Attic pressure is 29 Pa and Sample-register pressure is 17 Pa.

Difference is Q – Q’ and Q = C x Pn for P = 25 Pa
Q – Q’ = C x 25n - C' x 25n'
= 210 x 250.65 - 202 x 25 0.66
= 1724 - 1663
= 60 CFM

PD25 = (30 - 3) / 2 = 13.5 Pa
P'D25 = (29 - 14) / 2 = 7.5 Pa

Duct Factor = PD250.6 / [PD250.6 – P’D250.6]
= 13.5 0.6 / [13.5 0.6 - 7.5 0.6 ]
= 4.77 / ( 4.77 - 3.35 )
= 3.36 [unitless]

Attic Factor = (25 / PD25)0.655
= (25 / 13.5) 0.655
= 1.497 [unitless]

DLO25 = Difference x Duct Factor x Duct Envelope Volume Factor
= 60 CFM x 3.36 x 1.5
= 304 CFM25


803.10.2.2 GSCA Sources of Error:

The only significant source of error is in the value of Q - Q' . The PD25 and P'D25 are much, much more accurately known; their high accuracy results from two facts: each is normally obtained from 800 data points and "measured pressure is homogenously proportional to tested pressure". (When Tectite is used in default mode, 100 data are collected for each target pressure.) Since the constant of proportionality is estimated by any single observation, the expected output pressure at any desired input pressure is 799 times, over-determined.


 


Comment #84

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 6
Paragraph / Figure / Table / Note: 802.6
Comment Type: Editorial

Comment:

803.10 Generalized Subtraction Correction Algorithm (GSCA) for Duct Leakage-to-Outside testing. (Submitted by Myron Katz of Building Science Innovators, LLC)

The purpose of this test procedure is to determine duct leakage-to-outside of the conditioned space.

(Much if not most of the following content in this discourse, particularly until the beginning of section 803.10.1, finds its way into this document in order to require its careful review by the RESNET technical committee and RESNET Board according to ANSI standards on creating a standard. However, that is not to say that the authors of 803.10 believe that all this explanatory argumentation belongs in the final version of the published standard.)

This test is not intended to supplant the RESNET-Standard duct leakage-to-outside test described in 803.2 - 803.7 but, instead, to provide an alternative RESNET-approved standard that can be used when applicable. In many, if not most cases, when the current RESNET standard is applicable, GSCA can also be used, thereby providing many additional benefits.

GSCA cannot be used to measure Total Duct Leakage. Neither can GSCA be used to measure Duct Leakage-to-outside when parts of the duct system are located in more than one outside-of-the-thermal-envelope volumes like the crawl space and attic, multiple attics, or an attic and garage, etc. Neither can GSCA be used if there is more than one duct system. Moreover, like most of the other proposed, RESNET-approved, duct-leakage-testing protocols, GSCA does not separate supply from return duct leakage and GSCA does not measure the actual duct leakage while the HVAC system is running. It has a few other, but rarely found in practice, limitations as well; for example, GSCA expects a small drop in the duct-envelope-volume pressure when comparing the taped case to the untaped case: if this drop is greater than 1 Pa, problems of GSCA applicability occur. See the referenced engineering article at the end of this section for more details.

However, GSCA has much to recommend it:
1. GSCA requires less testing equipment. No duct-fan-pressurization tester is needed. However, for optimal accuracy, a fully-automated, data-collection system must be used. This typically includes two or three machines: 1) a laptop computer and 2) two DG700's or a four-manometer APT or equivalent. (There is a way to do this test without significant loss of accuracy with only two machines, i.e., only one DG700, but that will be left to the clever reader-experimenter to discover.) In the near future, the needed laptop computer may be replaced by a suitably-adapted, "smart" cell phone. However, these authors do not know of a case where a cell phone has been used to control a DG700 or similar manometer. (Check with one of the blower-door manufacturers for an recent update on this issue.) A non-scientific survey at the last two RESNET conferences suggest that about half of all raters already bring a laptop computer and a DG700 or equivalent to most jobs and almost as many already do multi-point, building-envelope-leakage testing.
2. GSCA requires less on-site rater time. GSCA can be performed while the rater is performing other tasks. Since the test is fully automated, the setup is the only time-consuming part. Most of the GSCA setup is already required for normal, blower-door testing anyway. Thus ... not much additional work is required. In fact, the extra work that is required is substantially less time-consuming than that required to merely setup a duct fan pressurization test.
3. GSCA has higher accuracy. As explained in the parenthetical notes within draft sections 803.2-7, the difference between two highly accurate automated multi-point tests should have an expected error substantially lower than the current RESNET-proposed, draft, duct-leakage-to-outside standard.
4. A paper trail is generated on all data collections and calculations. This trail improves the ability for the Quality Assurance Designee to confirm that building-envelope and duct-leakage testing was done correctly. Consequently, the large scale application of GSCA has the potential to increase the accuracy of both building and duct leakage testing for an even larger percentage of the industry.
5. GSCA facilitates ZPD. The data collection process of GSCA requires half or more of the data collections needed for Zone-Pressure Diagnostics (ZPD) and 90% of the setup ... thereby facilitating and directing weatherization programs and energy audits. This is particularly the case since moving the thermal boundary is the paramount first step to optimal energy auditing and ZPD is needed to optimally estimate the energy savings garnered by avoided infiltration resulting from the movement of the thermal boundary. GSCA requires the pressure monitoring of at least one non-conditioned volume within the building during an 8-point pressure test. This exposes the rater to observations that will enhance understanding of infiltration dynamics of that building. (The concept of an attic to house pressure-coupling ratio is an example of this.)
6. GSCA exposes errors in setup in real-time. The largest percentage of errors in setup is found when the rater sees in real-time both the non-linearity of the data collected as graphed on a log-log scale and the fluctuations and size of data recorded during baseline pressure testing. GSCA allows the rater to correct the setup errors before completing the first building envelope leakage test, any duct leakage test, dismantling the setup or leaving the job-site. Such errors are often never found, but when they are suspected hours to days later, much time and money are wasted.
7. GSCA requires less invasive, less time-consuming and less potentially equipment damaging setup. In particular, the filters of the duct system do not need to be removed. Neither do zone or bypass (not balancing) dampers need to be set to the open position to facilitate uniform pressures throughout the duct system.
8. GSCA can be fully automated by hardware manufacturers.
9. GSCA requires a full set of pressure-pan tests as part of the setup. This has the dual value of improving the accuracy and repeatability of GSCA and providing access to the pressure-pan data for more insight into where to concentrate duct-leakage-repair work.
10. With GSCA, duct-leakage testing is more integrated into building-envelope-leakage testing and zone-pressure diagnostics in a way that is optimally computer friendly and provided with real-time help to guide the rater to fix errors in setup. Thus GSCA provides a bridge to a platform for a fully-integrated, whole-building approach to more error-free data-collection to support auditing and weatherization.

Define the Duct Envelope Volume as the part of building that contains all of the duct system that is outside of conditioned space. In many homes this is the attic. For other buildings, it may be the garage, crawl space, or basement, etc. GSCA is not applicable if the duct system that is outside of conditioned space is located in a more than one combination of the above, or if the duct system is part of a package unit, where, for example, part of the HVAC unit is outside, part of the unit is in an attic or crawl space and the rest is in conditioned space; in these latter cases, the duct envelope volume is undefined.

GSCA purports to measure duct-leakage-to-outside when the pressure between the ducts and the duct envelope volume is 25 Pa. Unlike the alternative RESNET-standard, duct leakage-to-outside test, GSCA does not ignore changes in the duct-envelope-volume pressure.

To best appreciate, exploit and understand this concept, GSCA defines three terms:

PD = the pressure difference between the duct system and the duct envelope volume
for arbitrary induced building-pressure.

PD25 = the pressure difference between the duct system and the duct envelope volume when the induced building-pressure is 25 Pa.

P* = the induced building-pressure
when PD = 25 Pa.

Heretofore, any duct leakage test done at 25 Pa will actually measure flow at a pressure of PD25 even though PD25 is probably (and possibly significantly) less than 25 Pa. What is needed is a test of duct leakage where the equipment is set to run at P* in order to assure that is PD in fact 25 Pa. GSCA solves this problem and it does it without requiring extra data collections or opening doors that cannot be opened or cannot be easily opened.

Hereinafter, the ' or apostrophe placed after a pressure, coefficient, exponent or flow symbol refers to the taped case and the lack an apostrophe indicates the untaped case. I.e., Q = C x Pn is the flow equation for the untaped case and Q' = C' x Pn' is the flow equation for the taped case. Similarly, P'D corresponds to the pressure difference between the duct system and the duct envelope volume during a taped test.

When performing a GSCA, (duct-leakage-to-outside test,) a blower door is used to perform a pair of multi-point, building-envelope-leakage tests each as described in 802.6, but each are performed in a fully-automated fashion. However, to facilitate all data collections needed for GSCA, a few extra setup steps are required before the first, multi-point test is performed.

GSCA evolved from the Subtraction Method, and its daughter, Modified Subtraction. (Until c2000 or few years thereafter, Modified Subtraction was the only RESNET- approved duct-leakage-to-outside testing protocol.) Subtraction Method is based on the assumption that in the first approximation, duct-leakage-to-outside is the difference between two blower-door tests where the first is performed with ducts in their normal, untaped condition and the second blower door test is performed with the ducts masked or taped. Modified Subtraction utilizes a subtraction-correction factor to improve the Subtraction Method to accommodate the error arising from duct-leakage flows to inside that were undermining its accuracy; the subtraction-correction factor is calculated from a measured change in duct pressure during the two tests. GSCA improves upon Modified Subtraction by collecting the same data, and in addition, measuring pressure changes in the Duct Envelope Volume -- a pressure that is not always the same pressure as outside when the building is depressurized to 50 Pa. Although during the initial setup for the two building envelope tests needed for a GSCA calculation--one cannot know a priori which induced building-envelope pressure corresponds to a 25 Pa pressure-difference between the duct system and the duct envelope volume in the untaped case, that information is not needed at the beginning of the test to assure that this measurement is available when the test is over. That is, even though P* is not known in advance, we can still calculate the difference in flows at this pressure a posteriori, because the automated, multi-point-test controlling software outputs the parameters of the flow equation, Q = C x Pn, namely, the software reports the flow coefficient and flow exponent for each building-envelope-leakage test. Since measured pressure is homogeneously proportional to input pressure for all the duct pressure and duct envelope volume pressure data collected, we know that P* = 25 x (25 / PD25); thus P* can be input into both flow equations to calculate Q - Q' at the appropriate input pressure. However, to provide data of adequate accuracy, heretofore, all versions of blower-door subtraction had a fundamental fatal flaw: the desired duct leakage-to-outside to be calculated is often smaller than the error in the measurements of each of the two building-envelope-leakage measurements. To overcome this problem, GSCA is only recommended wherein the data is collected with automated performance testing equipment controlled by software, and even in these cases, the building envelope tests must be sufficiently precise to reliably obtain expected errors in CFM50 of less than 0.5% at a 95% confidence level. (At this writing, the author is not sure that this level of accuracy is needed, but it is easily available and will generate calculated duct leakage-to-outside measurement that will be reliably more accurate than competing, standard tests.) In that case, the two, building-envelope-leakage measurements can be made with sufficient accuracy that their difference has an expected error smaller than what the RESNET technical committee considers insignificant in its current duct-leakage-to-outside standard. The mathematical derivation of GSCA can be found in ASTM's Journal on Testing and Evaluation, November 2004, Volume 23, Number 6 or from its authors upon request.

803.10.1 GSCA Simplified-Test-Procedures:

For purposes of this chapter, duct leakage may be measured by either pressurizing or
depressurizing the building and duct system in two nearly consecutive blower-door tests; the first test is only slightly different from 802.6; the second test is exactly the same as the first test except it is performed after supply and return grilles are temporarily sealed in a manner that permits the separation of the duct system from the building at these standard duct system openings. Both building envelope leakage tests are fully-automated, multi-point tests performed with software that that controls the computer's data collections.

Two additional pressures are recorded multiple times at target induced-pressures:
a) The pressure in a sample supply or return register that is masked off for both the taped and untaped tests, and
b) The pressure in the duct envelope volume.

From these data, all of the benefits of GSCA can be harvested.

803.10.2 GSCA Detailed-Test-Procedures:

The following describes the test with depressurization, but GSCA can be performed equally well, and easily, with pressurization. Depressurization is usually preferred because it naturally closes most of the commonly-found, exhaust-vent dampers. It should also be noted that most of the testing work performed to setup for GSCA is already needed for otherwise-required, building-envelope-leakage testing.

803.10.2.1 GSCA Setup Procedures:

1. Setup the equipment but not the software for a multi-point building-envelope-leakage test as described in 802.6, but prepare hardware for a software-controlled computer to control the blower-door fan-speed and all data collections via a smart, dual or multi-channel manometer (similar to a DG700 or APT). Notice that this approach exceeds the 802.6 specifications since this system can perform all required multi-point data collections for a building-envelope-leakage test in a fully-automated fashion.
2. Perform a complete set of pressure-pan tests.
A) Let the software test the blower door against the building's leakiness following a one minute, baseline-monitoring-averaging measurement. Set the software to cruise the blower door at 50 Pa or the highest pressure below 50 Pa it can reach. Define H to be 60 Pa or the highest induced building-pressure below 60 Pa that can be reached by the blower door.
B) Assemble the pressure-pan system: connect a digital pressure gauge by a tube to a pressure pan that is attached to a pole to allow the rater to position the pressure pan over each supply or return grille in a fashion to significantly mask it and allow the rater to read the manometer.
C) Partially mask all supply and return grilles as needed to leave a hole of at least one sq ft or more but having a size and shape not to exceed the footprint of the pressure pan.
D) Name and list the names of each supply and return register in an electronic record. (Although this step can be done with paper, all of the rest of the data collections are electronic; therefore for a variety of goals including Quality Assurance, the plan is that this data is collected and stored via spreadsheet software like Excel.)
E) One by one, visit each supply and return grille, temporarily completely cover the unmasked opening in the grille with the pressure pan and read the pressure across that grille with respect to inside.
F) Record each datum adjacent to the appropriate grille's name. Also record the cruise pressure that was used for all the tests. For quality-assurance repeatability, specify which exterior door or window was used for the location of the blower door.
3. Choose the supply or return grille that is closest to the blower door, but more importantly, is closest to the pressure that is the average pressure found in all pressure-pan tests. This grille is defined to be the Sample Register.
4. Mask the sample register and place a pressure-sampling probe a few inches through the mask. Run the other end of this tube to the vicinity of the computer.
5. Run a tube into the duct enclosure volume; run the other end of this tube to the vicinity of the computer.
6. Using either a four-manometer or two dual manometers or equivalent equipment, connect all hardware and tubes via the manometers to the computer in a fashion so that four pressures can be simultaneously read and stored by the software. Two of these manometers should already be connected to outside and the blower door fan, since this was required in Step 1 above. The other two manometers receive the tubes coming from the sample register and the duct enclosure volume; both will be measured relative to inside pressure.

803.10.2.2 GSCA Testing Procedures:

1. Complete the setup of the software to perform the multi-point test to completely conform to 802.6 in a precisely repeatable fashion. This step exceeds Step 1 in section 803.10.2.1 and is only possible after Step 2 established, H, the highest possible, induced building-pressure. Set the software to use 8, equally-spaced, target induced building-pressures for data collections ranging from H down to 15 Pa, if possible. However, to optimize the accuracy and repeatability of the calculation of CFM50, choose the target pressures exactly as follows:
If H > 30 Pa, use G = (H - 15) / 7
If 20 < H < 30 Pa, use G = (H - 10) / 7.
If 15 < H < 20 Pa, use G = (H - 8) / 7.
If 11 < H < 15 Pa, use G = (H - 6) / 7.
If 8 < H < 11 Pa, use G = 1/2.
Choose the target building-pressure to be the greatest integer < :
H, H-G, H-2G, H-2G, H-4G, H-5G, H-6G, H-7G.

For example, if H were 35, then G = (35-15)/7 ~= 2.86 and the target pressures are:
35, 32, 29, 26, 23, 20, 17, 15.

For example, if H were 10, then G = 1/2 and the target pressures are:
10, 9, 9, 8, 8, 7, 7, 6

If H is less than 8 do not use GSCA. In fact, in practice, it may not be feasible to try to get such highly accurate CFM50 if H is less than 15 Pa. But with a really windless day, and/or by using a 2-minute test averaging period, such accuracy can often be reached, nonetheless. Input inside and outside temperatures and altitude data as the software requests. (Input into Tectite stack-effect and wind-shielding approximations as well. Although these last two are not needed for GSCA, they provide access to ELA which for some homes should be the preferred means for inputting parameters of building-leakiness into RESNET-approved energy rating software.)

2. Setup the software to record and report statistical data for the sample-register pressure and the duct-envelope-volume pressure for every data point collected above.
3. Run the automated, multi-point, building-envelope-leakage test by clicking the "start test" button in the software; change flow rings as needed.
4. Watch the data collection and look for and correct errors in setup.
A) Observe the real-time measurement of the pre-test baseline data to check for setup errors. (Are the values what you expect? Possible causes are running the attic fan. stack-effects (causing a negative pressure) a wind effect (causing fluctuations in the baseline readings)).
B) Observe the slowly forming, log-log graph of the collected (pressure, flow) data points to check the co-linearity of the data. If they are far from linear, stop the test and fix the setup errors before restarting the testing.
C) When the first test is complete, name and save the test. Notice the calculated error in CFM50 as well as the calculated correlation coefficient of the input data. Are they acceptable or do you need to repair the setup?
D) If needed, repair all errors in data collection and repeat the test. Consider that as the sun moves in the sky, stack effect and the effects of wind usually change.
E) Experience indicates that a correlation coefficient less than 0.99 is a poor result that can be repaired with slight improvements in the setup of the equipment. Correlation coefficients greater than 0.999 will happen very often if the rater is careful; these are very good results. However, if the baseline measurement is too large or H is too small, the rater will never get a very low expected error in CFM50 -- no matter how high the correlation coefficient.
5. After the rater has gained experience from performing this test in 10 homes, the rater will realize what accuracy can be expected after the first two tests at the next home. There is little payoff to try to improve testing when CFM50 has an error estimate below 0.5%. On the other hand, if the error estimate of CFM50 cannot be made better than 5% do not expect very good GSCA accuracy.
6. The rater should now have two (2) or more test result files for the duct grilles' untaped case.
7. Tape all duct grilles.
8. Repeat the automated test using the setup conditions of the most successful untaped case. Save the test and repeat.

803.10.2.2 GSCA Calculation Procedures:

1. Chose the most accurate untaped test and the most accurate taped test and input their data to the Duct Leakage Calculator, Excel file. (A version of it should accompany this document. The ELA datum requested within it is not used for GSCA.)
2. Duct leakage to outside at 25 Pa denoted by DLO25 is calculated by:

DLO25 = Difference x Duct Factor x Duct Envelope Volume Factor †

DLO25 = (Q – Q’) x (PD0.6/[PD0.6 – P’D0.6]) x (25/PD25)(n + n')/2

where ’ denotes taped and

Difference is Q – Q’ for P = 25 Pa, where Q = C x Pn

Both C and n have been stored by the software for both the taped and untaped cases.

Q – Q’ = C x 25n - C' x 25n'
(This flow factor is the first order subtraction, evaluated at 25 Pa.)

Duct Factor = PD250.6 / [PD250.6 – P’D250.6]
(This is a generalized version of the subtraction-correction factor.)

Duct Envelope Volume Factor = (25 / PD25) (n + n')/2
(This is new factor displays the effect of a change in duct-envelope-volume pressure.)


† (In fact, the most accurate way to calculate GSCA's DLO25 uses the following formula:

DLO25 = Difference|(P*) x Duct Envelope Volume Factor

DLO25 = (Q – Q’)|(P*) x (PD250.6/[PD250.6 – P’D250.6])
where
(Q – Q’)|(P*) = C x (P*)n - C' x (P*)n' for P* = 25 x ( 25 / PD25)
= C x (25x25/PD25)n - C' x (25x25/PD25)n'
{This formula for P* is found just after equation 20 in the ASTM paper.}

However, for very small differences between n and n',
(Q – Q’)|(P*) is negligibly different from
(C x (25)n - C' x (25)n' ) x (25/ PD25)(n + n')/2 i.e., the first formula.

The first formula for GSCA calculation of DLO25 was presented initially and used in the freely distributable, GSCA duct leakage calculator for two reasons.
i) The first formula better facilitates understanding regarding the direct effect of the change in duct-envelope-volume pressure on the calculated duct-leakage-to-outside result because it is a separate factor.
ii) The down-side of this conceptually-clarifying formula is a very small error: it's use generates an error in the result on the order of 0.3% when changes in the flow exponent from untaped to taped are on the order of 0.01 -- a change in n that should not be expected to be exceeded. Thus the duct leakage calculator uses the first formula presented herein to present a slightly less accurate but much more explanatory calculation method than what the most accurate GSCA system should use.
For optimal accuracy, this second formula should be implemented in any fully-automated version of GSCA even though the first formula belongs in the freely distributable, GSCA-DuctLeakageCalculator.xls.)

Sample Calculation:

This is a sample calculation with the attic is the duct envelope volume.

Results from an untaped test home depressurized to 50 Pa :
Flow formula for untaped is Q = 210 * P 0.65,
Attic pressure is 30 Pa and Sample-register pressure is 3 Pa.

Results from the same home with ducts taped and depressurized to 50 Pa:
Flow formula for taped is Q = 202 * P 0.66,
Attic pressure is 29 Pa and Sample-register pressure is 17 Pa.

Difference is Q – Q’ and Q = C x Pn for P = 25 Pa
Q – Q’ = C x 25n - C' x 25n'
= 210 x 250.65 - 202 x 25 0.66
= 1724 - 1663
= 60 CFM

PD25 = (30 - 3) / 2 = 13.5 Pa
P'D25 = (29 - 14) / 2 = 7.5 Pa

Duct Factor = PD250.6 / [PD250.6 – P’D250.6]
= 13.5 0.6 / [13.5 0.6 - 7.5 0.6 ]
= 4.77 / ( 4.77 - 3.35 )
= 3.36 [unitless]

Attic Factor = (25 / PD25)0.655
= (25 / 13.5) 0.655
= 1.497 [unitless]

DLO25 = Difference x Duct Factor x Duct Envelope Volume Factor
= 60 CFM x 3.36 x 1.5
= 304 CFM25


803.10.2.2 GSCA Sources of Error:

The only significant source of error is in the value of Q - Q' . The PD25 and P'D25 are much, much more accurately known; their high accuracy results from two facts: each is normally obtained from 800 data points and "measured pressure is homogenously proportional to tested pressure". (When Tectite is used in default mode, 100 data are collected for each target pressure.) Since the constant of proportionality is estimated by any single observation, the expected output pressure at any desired input pressure is 799 times, over-determined.


 

Justification for Change:

mostly hyphens ...

replacement of time-averaging period with test-averaging period.

changed "software program" to "software".

Proposed Change:

802.6 Procedure for conducting a multi-point airtightness test:
1. Equipment that can automatically perform a multi-point test may be used to
perform the steps below.
2. With the blower-door fan sealed and off, measure and record the pre-test
baseline building pressure reading with respect to outside. This measurement
shall be taken over a test-averaging period of at least 10 seconds and shall
have a resolution of 0.1 Pa. Record the pre-test baseline building pressure
measurement.
3. Unseal the blower-door fan. Turn on and adjust the fan to create an induced
building-pressure of approximately 60 Pa. If a 60 Pa induced building-pressure
cannot be achieved because the blower door fan does not have sufficient flow
capacity, then adjust the fan to achieve the highest induced building-pressure
possible.
Measure the unadjusted building-pressure (not baseline adjusted) and nominal
fan flow (neither temperature- nor altitude-corrected) using the same test-averaging
period used in Step 2 in section 802.6. Record the unadjusted
building-pressure (with 0.1 Pa resolution), nominal fan flow (with 1 CFM
resolution), fan configuration, fan model and fan serial number. Assure that
the fan is being operated according to the manufacturer’s instructions.
Note: since both pre- and post-test baseline measurements are required, do not
use any baseline-adjustment feature of the manometer. In addition, do not use
an “@50 Pa” feature because the nominal fan flow shall be recorded.
4. Take and record a minimum of 7 additional unadjusted building pressure and
nominal fan flow measurements at target induced-pressures which are
approximately equally-spaced between 60 Pa (or the highest achievable
induced building pressure) and 15 Pa. In very leaky buildings, the low end of
this range may be reduced to as little as 4 Pa plus the absolute value of the pre-test
baseline pressure.
5. Turn off and seal the blower door fan.
7
6. Measure and record the post-test baseline building pressure reading with
respect to outside. This measurement shall be taken over the same test-averaging
period used in Step 2 and shall have a resolution of 0.1 Pa. Record
the post-test baseline building pressure measurement.
7. Enter the recorded test values, temperatures and altitude into software
that can perform the necessary calculations in accordance with ASTM
E779.
The software shall calculate and report: corrected CFM50 and the
percent uncertainty in the corrected CFM50 at the 95% confidence level, as
defined in ASTM E779.
Although ACH50 may be reported, this calculation may be omitted if the
ACH50 metric is not needed.
Note: To avoid a higher percent uncertainty than desired, the testing technician
may choose a larger, test-averaging period and start over at Step 2 in section
802.6.


Comment #85

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 6
Paragraph / Figure / Table / Note: 802.6 section 7
Comment Type: Technical

Comment:

7. Enter the recorded test values, temperatures and altitude into a software
program that can perform the necessary calculations in accordance with ASTM
E779.
The software program shall calculate and report: corrected CFM50 and the
percent uncertainty in the corrected CFM50, at the 95% confidence level, as
defined in ASTM E779.
Although ACH50 may be reported, this calculation may be omitted if the
ACH50 metric is not needed.
Note: To avoid a higher percent uncertainty than desired, the testing technician
may choose a larger, time-averaging period and start over at Step 2 in section
802.6.
 

Justification for Change:

The software-calculated uncertainly is more substantially and consistently the consequence of the extent that the 8 data points are not collinear as plotted on log-log paper. Invariably, fluctuating wind or errors in setup cause effectively all deviations in the linearity of the input data. Look for and correct these errors and repeat the test before increasing the test-averaging period. The data collection will also be grossly facilitated and the uncertainly grossly diminished if the data is collected by computer in an automated fashion. In this case, the experienced rater will customarily observe CFM50 error estimates in the <0.5% range -- corresponding to a 95% confidence level that the error in the CFM50 reading will be less than 25 (and a CFM25 error less than 12.5). (When a variant of blower door subtraction is used to measure duct leakage, such accuracy is needed and as I can show from my data, this is kind of accuracy is quite accessible.) 

 

For this reason and others, I am submitting GSCA.. Section 803.10:

Proposed Change:

803 ON-SITE INSPECTION PROCEDURES FOR DUCT LEAKAGE TESTING (continued)

803.10 Generalized Subtraction Correction Algorithm (GSCA) for Duct Leakage-to-Outside testing. (Submitted by Myron Katz of Building Science Innovators, LLC)

The purpose of this test procedure is to determine duct leakage-to-outside of the conditioned space.

(Much if not most of the following content in this discourse, particularly until the beginning of section 803.10.1, finds its way into this document in order to require its careful review by the RESNET technical committee and RESNET Board according to ANSI standards on creating a standard. However, that is not to say that the authors of 803.10 believe that all this explanatory argumentation belongs in the final version of the published standard.)

This test is not intended to supplant the RESNET-Standard duct leakage-to-outside test described in 803.2 - 803.7 but, instead, to provide an alternative RESNET-approved standard that can be used when applicable. In many, if not most cases, when the current RESNET standard is applicable, GSCA can also be used, thereby providing many additional benefits.

GSCA cannot be used to measure Total Duct Leakage. Neither can GSCA be used to measure Duct Leakage-to-outside when parts of the duct system are located in more than one outside-of-the-thermal-envelope volumes like the crawl space and attic, multiple attics, or an attic and garage, etc. Neither can GSCA be used if there is more than one duct system. Moreover, like most of the other proposed, RESNET-approved, duct-leakage-testing protocols, GSCA does not separate supply from return duct leakage and GSCA does not measure the actual duct leakage while the HVAC system is running. It has a few other, but rarely found in practice, limitations as well; for example, GSCA expects a small drop in the duct-envelope-volume pressure when comparing the taped case to the untaped case: if this drop is greater than 1 Pa, problems of GSCA applicability occur. See the referenced engineering article at the end of this section for more details.

However, GSCA has much to recommend it:
1. GSCA requires less testing equipment. No duct-fan-pressurization tester is needed. However, for optimal accuracy, a fully-automated, data-collection system must be used. This typically includes two or three machines: 1) a laptop computer and 2) two DG700's or a four-manometer APT or equivalent. (There is a way to do this test without significant loss of accuracy with only two machines, i.e., only one DG700, but that will be left to the clever reader-experimenter to discover.) In the near future, the needed laptop computer may be replaced by a suitably-adapted, "smart" cell phone. However, these authors do not know of a case where a cell phone has been used to control a DG700 or similar manometer. (Check with one of the blower-door manufacturers for an recent update on this issue.) A non-scientific survey at the last two RESNET conferences suggest that about half of all raters already bring a laptop computer and a DG700 or equivalent to most jobs and almost as many already do multi-point, building-envelope-leakage testing.
2. GSCA requires less on-site rater time. GSCA can be performed while the rater is performing other tasks. Since the test is fully automated, the setup is the only time-consuming part. Most of the GSCA setup is already required for normal, blower-door testing anyway. Thus ... not much additional work is required. In fact, the extra work that is required is substantially less time-consuming than that required to merely setup a duct fan pressurization test.
3. GSCA has higher accuracy. As explained in the parenthetical notes within draft sections 803.2-7, the difference between two highly accurate automated multi-point tests should have an expected error substantially lower than the current RESNET-proposed, draft, duct-leakage-to-outside standard.
4. A paper trail is generated on all data collections and calculations. This trail improves the ability for the Quality Assurance Designee to confirm that building-envelope and duct-leakage testing was done correctly. Consequently, the large scale application of GSCA has the potential to increase the accuracy of both building and duct leakage testing for an even larger percentage of the industry.
5. GSCA facilitates ZPD. The data collection process of GSCA requires half or more of the data collections needed for Zone-Pressure Diagnostics (ZPD) and 90% of the setup ... thereby facilitating and directing weatherization programs and energy audits. This is particularly the case since moving the thermal boundary is the paramount first step to optimal energy auditing and ZPD is needed to optimally estimate the energy savings garnered by avoided infiltration resulting from the movement of the thermal boundary. GSCA requires the pressure monitoring of at least one non-conditioned volume within the building during an 8-point pressure test. This exposes the rater to observations that will enhance understanding of infiltration dynamics of that building. (The concept of an attic to house pressure-coupling ratio is an example of this.)
6. GSCA exposes errors in setup in real-time. The largest percentage of errors in setup is found when the rater sees in real-time both the non-linearity of the data collected as graphed on a log-log scale and the fluctuations and size of data recorded during baseline pressure testing. GSCA allows the rater to correct the setup errors before completing the first building envelope leakage test, any duct leakage test, dismantling the setup or leaving the job-site. Such errors are often never found, but when they are suspected hours to days later, much time and money are wasted.
7. GSCA requires less invasive, less time-consuming and less potentially equipment damaging setup. In particular, the filters of the duct system do not need to be removed. Neither do zone or bypass (not balancing) dampers need to be set to the open position to facilitate uniform pressures throughout the duct system.
8. GSCA can be fully automated by hardware manufacturers.
9. GSCA requires a full set of pressure-pan tests as part of the setup. This has the dual value of improving the accuracy and repeatability of GSCA and providing access to the pressure-pan data for more insight into where to concentrate duct-leakage-repair work.
10. With GSCA, duct-leakage testing is more integrated into building-envelope-leakage testing and zone-pressure diagnostics in a way that is optimally computer friendly and provided with real-time help to guide the rater to fix errors in setup. Thus GSCA provides a bridge to a platform for a fully-integrated, whole-building approach to more error-free data-collection to support auditing and weatherization.

Define the Duct Envelope Volume as the part of building that contains all of the duct system that is outside of conditioned space. In many homes this is the attic. For other buildings, it may be the garage, crawl space, or basement, etc. GSCA is not applicable if the duct system that is outside of conditioned space is located in a more than one combination of the above, or if the duct system is part of a package unit, where, for example, part of the HVAC unit is outside, part of the unit is in an attic or crawl space and the rest is in conditioned space; in these latter cases, the duct envelope volume is undefined.

GSCA purports to measure duct-leakage-to-outside when the pressure between the ducts and the duct envelope volume is 25 Pa. Unlike the alternative RESNET-standard, duct leakage-to-outside test, GSCA does not ignore changes in the duct-envelope-volume pressure.

To best appreciate, exploit and understand this concept, GSCA defines three terms:

PD = the pressure difference between the duct system and the duct envelope volume
for arbitrary induced building-pressure.

PD25 = the pressure difference between the duct system and the duct envelope volume when the induced building-pressure is 25 Pa.

P* = the induced building-pressure
when PD = 25 Pa.

Heretofore, any duct leakage test done at 25 Pa will actually measure flow at a pressure of PD25 even though PD25 is probably (and possibly significantly) less than 25 Pa. What is needed is a test of duct leakage where the equipment is set to run at P* in order to assure that is PD in fact 25 Pa. GSCA solves this problem and it does it without requiring extra data collections or opening doors that cannot be opened or cannot be easily opened.

Hereinafter, the ' or apostrophe placed after a pressure, coefficient, exponent or flow symbol refers to the taped case and the lack an apostrophe indicates the untaped case. I.e., Q = C x Pn is the flow equation for the untaped case and Q' = C' x Pn' is the flow equation for the taped case. Similarly, P'D corresponds to the pressure difference between the duct system and the duct envelope volume during a taped test.

When performing a GSCA, (duct-leakage-to-outside test,) a blower door is used to perform a pair of multi-point, building-envelope-leakage tests each as described in 802.6, but each are performed in a fully-automated fashion. However, to facilitate all data collections needed for GSCA, a few extra setup steps are required before the first, multi-point test is performed.

GSCA evolved from the Subtraction Method, and its daughter, Modified Subtraction. (Until c2000 or few years thereafter, Modified Subtraction was the only RESNET- approved duct-leakage-to-outside testing protocol.) Subtraction Method is based on the assumption that in the first approximation, duct-leakage-to-outside is the difference between two blower-door tests where the first is performed with ducts in their normal, untaped condition and the second blower door test is performed with the ducts masked or taped. Modified Subtraction utilizes a subtraction-correction factor to improve the Subtraction Method to accommodate the error arising from duct-leakage flows to inside that were undermining its accuracy; the subtraction-correction factor is calculated from a measured change in duct pressure during the two tests. GSCA improves upon Modified Subtraction by collecting the same data, and in addition, measuring pressure changes in the Duct Envelope Volume -- a pressure that is not always the same pressure as outside when the building is depressurized to 50 Pa. Although during the initial setup for the two building envelope tests needed for a GSCA calculation--one cannot know a priori which induced building-envelope pressure corresponds to a 25 Pa pressure-difference between the duct system and the duct envelope volume in the untaped case, that information is not needed at the beginning of the test to assure that this measurement is available when the test is over. That is, even though P* is not known in advance, we can still calculate the difference in flows at this pressure a posteriori, because the automated, multi-point-test controlling software outputs the parameters of the flow equation, Q = C x Pn, namely, the software reports the flow coefficient and flow exponent for each building-envelope-leakage test. Since measured pressure is homogeneously proportional to input pressure for all the duct pressure and duct envelope volume pressure data collected, we know that P* = 25 x (25 / PD25); thus P* can be input into both flow equations to calculate Q - Q' at the appropriate input pressure. However, to provide data of adequate accuracy, heretofore, all versions of blower-door subtraction had a fundamental fatal flaw: the desired duct leakage-to-outside to be calculated is often smaller than the error in the measurements of each of the two building-envelope-leakage measurements. To overcome this problem, GSCA is only recommended wherein the data is collected with automated performance testing equipment controlled by software, and even in these cases, the building envelope tests must be sufficiently precise to reliably obtain expected errors in CFM50 of less than 0.5% at a 95% confidence level. (At this writing, the author is not sure that this level of accuracy is needed, but it is easily available and will generate calculated duct leakage-to-outside measurement that will be reliably more accurate than competing, standard tests.) In that case, the two, building-envelope-leakage measurements can be made with sufficient accuracy that their difference has an expected error smaller than what the RESNET technical committee considers insignificant in its current duct-leakage-to-outside standard. The mathematical derivation of GSCA can be found in ASTM's Journal on Testing and Evaluation, November 2004, Volume 23, Number 6 or from its authors upon request.

803.10.1 GSCA Simplified-Test-Procedures:

For purposes of this chapter, duct leakage may be measured by either pressurizing or
depressurizing the building and duct system in two nearly consecutive blower-door tests; the first test is only slightly different from 802.6; the second test is exactly the same as the first test except it is performed after supply and return grilles are temporarily sealed in a manner that permits the separation of the duct system from the building at these standard duct system openings. Both building envelope leakage tests are fully-automated, multi-point tests performed with software that that controls the computer's data collections.

Two additional pressures are recorded multiple times at target induced-pressures:
a) The pressure in a sample supply or return register that is masked off for both the taped and untaped tests, and
b) The pressure in the duct envelope volume.

From these data, all of the benefits of GSCA can be harvested.

803.10.2 GSCA Detailed-Test-Procedures:

The following describes the test with depressurization, but GSCA can be performed equally well, and easily, with pressurization. Depressurization is usually preferred because it naturally closes most of the commonly-found, exhaust-vent dampers. It should also be noted that most of the testing work performed to setup for GSCA is already needed for otherwise-required, building-envelope-leakage testing.

803.10.2.1 GSCA Setup Procedures:

1. Setup the equipment but not the software for a multi-point building-envelope-leakage test as described in 802.6, but prepare hardware for a software-controlled computer to control the blower-door fan-speed and all data collections via a smart, dual or multi-channel manometer (similar to a DG700 or APT). Notice that this approach exceeds the 802.6 specifications since this system can perform all required multi-point data collections for a building-envelope-leakage test in a fully-automated fashion.
2. Perform a complete set of pressure-pan tests.
A) Let the software test the blower door against the building's leakiness following a one minute, baseline-monitoring-averaging measurement. Set the software to cruise the blower door at 50 Pa or the highest pressure below 50 Pa it can reach. Define H to be 60 Pa or the highest induced building-pressure below 60 Pa that can be reached by the blower door.
B) Assemble the pressure-pan system: connect a digital pressure gauge by a tube to a pressure pan that is attached to a pole to allow the rater to position the pressure pan over each supply or return grille in a fashion to significantly mask it and allow the rater to read the manometer.
C) Partially mask all supply and return grilles as needed to leave a hole of at least one sq ft or more but having a size and shape not to exceed the footprint of the pressure pan.
D) Name and list the names of each supply and return register in an electronic record. (Although this step can be done with paper, all of the rest of the data collections are electronic; therefore for a variety of goals including Quality Assurance, the plan is that this data is collected and stored via spreadsheet software like Excel.)
E) One by one, visit each supply and return grille, temporarily completely cover the unmasked opening in the grille with the pressure pan and read the pressure across that grille with respect to inside.
F) Record each datum adjacent to the appropriate grille's name. Also record the cruise pressure that was used for all the tests. For quality-assurance repeatability, specify which exterior door or window was used for the location of the blower door.
3. Choose the supply or return grille that is closest to the blower door, but more importantly, is closest to the pressure that is the average pressure found in all pressure-pan tests. This grille is defined to be the Sample Register.
4. Mask the sample register and place a pressure-sampling probe a few inches through the mask. Run the other end of this tube to the vicinity of the computer.
5. Run a tube into the duct enclosure volume; run the other end of this tube to the vicinity of the computer.
6. Using either a four-manometer or two dual manometers or equivalent equipment, connect all hardware and tubes via the manometers to the computer in a fashion so that four pressures can be simultaneously read and stored by the software. Two of these manometers should already be connected to outside and the blower door fan, since this was required in Step 1 above. The other two manometers receive the tubes coming from the sample register and the duct enclosure volume; both will be measured relative to inside pressure.

803.10.2.2 GSCA Testing Procedures:

1. Complete the setup of the software to perform the multi-point test to completely conform to 802.6 in a precisely repeatable fashion. This step exceeds Step 1 in section 803.10.2.1 and is only possible after Step 2 established, H, the highest possible, induced building-pressure. Set the software to use 8, equally-spaced, target induced building-pressures for data collections ranging from H down to 15 Pa, if possible. However, to optimize the accuracy and repeatability of the calculation of CFM50, choose the target pressures exactly as follows:
If H > 30 Pa, use G = (H - 15) / 7
If 20 < H < 30 Pa, use G = (H - 10) / 7.
If 15 < H < 20 Pa, use G = (H - 8) / 7.
If 11 < H < 15 Pa, use G = (H - 6) / 7.
If 8 < H < 11 Pa, use G = 1/2.
Choose the target building-pressure to be the greatest integer < :
H, H-G, H-2G, H-2G, H-4G, H-5G, H-6G, H-7G.

For example, if H were 35, then G = (35-15)/7 ~= 2.86 and the target pressures are:
35, 32, 29, 26, 23, 20, 17, 15.

For example, if H were 10, then G = 1/2 and the target pressures are:
10, 9, 9, 8, 8, 7, 7, 6

If H is less than 8 do not use GSCA. In fact, in practice, it may not be feasible to try to get such highly accurate CFM50 if H is less than 15 Pa. But with a really windless day, and/or by using a 2-minute test averaging period, such accuracy can often be reached, nonetheless. Input inside and outside temperatures and altitude data as the software requests. (Input into Tectite stack-effect and wind-shielding approximations as well. Although these last two are not needed for GSCA, they provide access to ELA which for some homes should be the preferred means for inputting parameters of building-leakiness into RESNET-approved energy rating software.)

2. Setup the software to record and report statistical data for the sample-register pressure and the duct-envelope-volume pressure for every data point collected above.
3. Run the automated, multi-point, building-envelope-leakage test by clicking the "start test" button in the software; change flow rings as needed.
4. Watch the data collection and look for and correct errors in setup.
A) Observe the real-time measurement of the pre-test baseline data to check for setup errors. (Are the values what you expect? Possible causes are running the attic fan. stack-effects (causing a negative pressure) a wind effect (causing fluctuations in the baseline readings)).
B) Observe the slowly forming, log-log graph of the collected (pressure, flow) data points to check the co-linearity of the data. If they are far from linear, stop the test and fix the setup errors before restarting the testing.
C) When the first test is complete, name and save the test. Notice the calculated error in CFM50 as well as the calculated correlation coefficient of the input data. Are they acceptable or do you need to repair the setup?
D) If needed, repair all errors in data collection and repeat the test. Consider that as the sun moves in the sky, stack effect and the effects of wind usually change.
E) Experience indicates that a correlation coefficient less than 0.99 is a poor result that can be repaired with slight improvements in the setup of the equipment. Correlation coefficients greater than 0.999 will happen very often if the rater is careful; these are very good results. However, if the baseline measurement is too large or H is too small, the rater will never get a very low expected error in CFM50 -- no matter how high the correlation coefficient.
5. After the rater has gained experience from performing this test in 10 homes, the rater will realize what accuracy can be expected after the first two tests at the next home. There is little payoff to try to improve testing when CFM50 has an error estimate below 0.5%. On the other hand, if the error estimate of CFM50 cannot be made better than 5% do not expect very good GSCA accuracy.
6. The rater should now have two (2) or more test result files for the duct grilles' untaped case.
7. Tape all duct grilles.
8. Repeat the automated test using the setup conditions of the most successful untaped case. Save the test and repeat.

803.10.2.2 GSCA Calculation Procedures:

1. Chose the most accurate untaped test and the most accurate taped test and input their data to the Duct Leakage Calculator, Excel file. (A version of it should accompany this document. The ELA datum requested within it is not used for GSCA.)
2. Duct leakage to outside at 25 Pa denoted by DLO25 is calculated by:

DLO25 = Difference x Duct Factor x Duct Envelope Volume Factor †

DLO25 = (Q – Q’) x (PD0.6/[PD0.6 – P’D0.6]) x (25/PD25)(n + n')/2

where ’ denotes taped and

Difference is Q – Q’ for P = 25 Pa, where Q = C x Pn

Both C and n have been stored by the software for both the taped and untaped cases.

Q – Q’ = C x 25n - C' x 25n'
(This flow factor is the first order subtraction, evaluated at 25 Pa.)

Duct Factor = PD250.6 / [PD250.6 – P’D250.6]
(This is a generalized version of the subtraction-correction factor.)

Duct Envelope Volume Factor = (25 / PD25) (n + n')/2
(This is new factor displays the effect of a change in duct-envelope-volume pressure.)


† (In fact, the most accurate way to calculate GSCA's DLO25 uses the following formula:

DLO25 = Difference|(P*) x Duct Envelope Volume Factor

DLO25 = (Q – Q’)|(P*) x (PD250.6/[PD250.6 – P’D250.6])
where
(Q – Q’)|(P*) = C x (P*)n - C' x (P*)n' for P* = 25 x ( 25 / PD25)
= C x (25x25/PD25)n - C' x (25x25/PD25)n'
{This formula for P* is found just after equation 20 in the ASTM paper.}

However, for very small differences between n and n',
(Q – Q’)|(P*) is negligibly different from
(C x (25)n - C' x (25)n' ) x (25/ PD25)(n + n')/2 i.e., the first formula.

The first formula for GSCA calculation of DLO25 was presented initially and used in the freely distributable, GSCA duct leakage calculator for two reasons.
i) The first formula better facilitates understanding regarding the direct effect of the change in duct-envelope-volume pressure on the calculated duct-leakage-to-outside result because it is a separate factor.
ii) The down-side of this conceptually-clarifying formula is a very small error: it's use generates an error in the result on the order of 0.3% when changes in the flow exponent from untaped to taped are on the order of 0.01 -- a change in n that should not be expected to be exceeded. Thus the duct leakage calculator uses the first formula presented herein to present a slightly less accurate but much more explanatory calculation method than what the most accurate GSCA system should use.
For optimal accuracy, this second formula should be implemented in any fully-automated version of GSCA even though the first formula belongs in the freely distributable, GSCA-DuctLeakageCalculator.xls.)

Sample Calculation:

This is a sample calculation with the attic is the duct envelope volume.

Results from an untaped test home depressurized to 50 Pa :
Flow formula for untaped is Q = 210 * P 0.65,
Attic pressure is 30 Pa and Sample-register pressure is 3 Pa.

Results from the same home with ducts taped and depressurized to 50 Pa:
Flow formula for taped is Q = 202 * P 0.66,
Attic pressure is 29 Pa and Sample-register pressure is 17 Pa.

Difference is Q – Q’ and Q = C x Pn for P = 25 Pa
Q – Q’ = C x 25n - C' x 25n'
= 210 x 250.65 - 202 x 25 0.66
= 1724 - 1663
= 60 CFM

PD25 = (30 - 3) / 2 = 13.5 Pa
P'D25 = (29 - 14) / 2 = 7.5 Pa

Duct Factor = PD250.6 / [PD250.6 – P’D250.6]
= 13.5 0.6 / [13.5 0.6 - 7.5 0.6 ]
= 4.77 / ( 4.77 - 3.35 )
= 3.36 [unitless]

Attic Factor = (25 / PD25)0.655
= (25 / 13.5) 0.655
= 1.497 [unitless]

DLO25 = Difference x Duct Factor x Duct Envelope Volume Factor
= 60 CFM x 3.36 x 1.5
= 304 CFM25


803.10.2.2 GSCA Sources of Error:

The only significant source of error is in the value of Q - Q' . The PD25 and P'D25 are much, much more accurately known; their high accuracy results from two facts: each is normally obtained from 800 data points and "measured pressure is homogenously proportional to tested pressure". (When Tectite is used in default mode, 100 data are collected for each target pressure.) Since the constant of proportionality is estimated by any single observation, the expected output pressure at any desired input pressure is 799 times, over-determined.


 


Comment #86

Amendment: Standards for Performance Testing (New Chapter 8)
Page Number: 7 & 8
Paragraph / Figure / Table / Note: 802.7
Comment Type: Editorial

Comment:

802.7 Procedure for conducting a repeated single point test:
1. With the blower door fan sealed and off, measure and record the pre-test
baseline building pressure reading with respect to outside. This measurement
shall be taken over a time-averaging period of at least 10 seconds and shall
have a resolution of 0.1 Pa. Record this value as the pre-test baseline building
pressure measurement.
2. Unseal the blower door fan. Turn on and adjust the fan to create an induced
building pressure of approximately 50 Pa. If a 50 Pa induced building pressure
can not be achieved because the blower door fan does not have sufficient flow
capacity, then achieve the highest induced building pressure possible with the
equipment available.
3. If during any single repeat of this test, the induced building pressure is less
than 15 Pa, recheck that the house set up is correct and determine if any basic
repairs are needed prior to further testing or modeling of the building.
Following any repairs or changes to the set up, the test shall be restarted from
the beginning. If you can not reach at least 15 Pa every time, then use the
procedures in sections 802.5 or 802.6.
8
4. Measure and record the unadjusted building pressure and nominal (not
temperature and altitude corrected) fan flow using the same time-averaging
period used in Step 1 in section 802.6 above. Record the unadjusted building
pressure (with 0.1 Pa resolution), nominal fan flow (with 1 CFM resolution),
fan configuration (rings, pressurization or depressurization, etc), fan model and
fan serial number.
Note: If your pressure gauge has the capability to display the induced building
pressure (i.e. baseline adjustment feature) and the capability to adjust the fan
flow value to an induced building pressure of 50 Pa (i.e. “@50 Pa” feature),
then follow the manufacturer’s procedures for calculating the results of a onepoint
test and record the following values: induced building pressure, nominal
CFM50, fan configuration, fan model and fan serial number.
5. Turn off the fan.
6. Calculate the following values:
?? induced building pressure = unadjusted building pressure (Pa) minus
pre-test baseline building pressure (Pa). Note: If a baseline adjustment
feature was used, then the induced building pressure is displayed on the
pressure gauge.
?? nominal CFM50 = (50 Pa / Induced building pressure) 0.65 x nominal
fan flow.
Note: If both a baseline adjustment feature and an “@50 Pa” feature were
used, the nominal CFM50 is displayed directly on the pressure gauge.
7. Repeat Steps 1-5 of section 802.7 until a minimum of 5 nominal CFM50
estimates have been recorded. The same fan configuration shall be used for
each repeat.
8. Calculate the Average Nominal CFM50 by summing the individual nominal
CFM50 readings and dividing by the number of readings.
9. If the altitude is above 5,000 feet or the difference between the inside and
outside temperature is more than 30 degrees Fahrenheit then calculate the
corrected CFM50 as defined below:
Calculate the Average Corrected CFM50 =
Average Nominal CFM50 x altitude correction factor x
temperature correction factor
where
altitude correction factor = 1 + .000006 x altitude,
altitude is in feet
temperature correction factors
are listed in Table 802.1

Justification for Change:

mostly hyphens

Proposed Change:

802.7 Procedure for conducting a repeated single-point test:
1. With the blower-door fan sealed and off, measure and record the pre-test
baseline building pressure reading with respect to outside. This measurement
shall be taken over a test-averaging period of at least 10 seconds and shall
have a resolution of 0.1 Pa. Record this value as the pre-test baseline building
pressure measurement.
2. Unseal the blower door fan. Turn on and adjust the fan to create an induced
building-pressure of approximately 50 Pa. If a 50 Pa, induced building-pressure
can not be achieved because the blower door fan does not have sufficient flow
capacity, then achieve the highest induced building-pressure possible with the
equipment available.
3. If during any single repeat of this test, the induced building-pressure can not reach at least 15 Pa, recheck that the house setup is correct and determine if any basic
repairs are needed prior to further testing or modeling of the building.
Following any repairs or changes to the setup, the test shall be restarted from
the beginning. If you can not reach at least 15 Pa every time, then use the
procedures in sections 802.5 or 802.6.
8
4. Measure and record the unadjusted building-pressure and nominal (neither
temperature- nor altitude-corrected) fan flow using the same test-averaging
period used in Step 1 in section 802.6 above. Record the unadjusted building-
pressure (with 0.1 Pa resolution), nominal fan flow (with 1 CFM resolution),
fan configuration (rings, pressurization or depressurization, etc), fan model and
fan serial number.
Note: If your pressure gauge has the capability to display the induced building-
pressure (i.e. baseline adjustment feature) and the capability to adjust the fan
flow value to an induced building-pressure of 50 Pa (i.e. “@50 Pa” feature),
then follow the manufacturer’s procedures for calculating the results of a one-point
test and record the following values: induced building-pressure, nominal
CFM50, fan configuration, fan model and fan serial number.
5. Turn off the fan.
6. Calculate the following values:
?? induced building-pressure = unadjusted building-pressure (Pa) minus
pre-test baseline building-pressure (Pa). Note: If a baseline adjustment
feature were used, then the induced building-pressure is displayed on the
pressure gauge.
?? nominal CFM50 = (50 Pa / induced building-pressure) 0.65 x nominal
fan flow.
Note: If both a baseline adjustment feature and an “@50 Pa” feature were
used, the nominal CFM50 is displayed directly on the pressure gauge.
7. Repeat Steps 1-5 of section 802.7 until a minimum of 5, nominal CFM50
estimates have been recorded. The same fan configuration shall be used for
each repeat.
8. Calculate the Average Nominal CFM50 by summing the individual nominal
CFM50 readings and dividing by the number of readings.
9. If the altitude is above 5,000 feet or the difference between the inside and
outside temperature is more than 30 degrees Fahrenheit then calculate the
corrected CFM50 as defined below:
Calculate the Average Corrected CFM50 =
Average Nominal CFM50 x altitude correction factor x
temperature correction factor
where
altitude correction factor = 1 + .000006 x altitude,
altitude is in feet
temperature correction factors
are listed in Table 802.1
 

12. If statistical software program is used, it shall, at a minimum, calculate and report:
1. Average CFM50, corrected for altitude and temperature
2. The percent uncertainty in the CFM50, at the 95% confidence level, as
calculated in step 11.
3. ACH50 (air changes per hour @ 50 Pa) = (CFM50 x 60) / building volume
(in cubic feet). This calculation may be omitted if the ACH50 metric is not
needed.
13. If the reported uncertainty in the CFM50 is less than or equal to 10.0%, then
the airtightness test shall be classified as a Standard Level of Accuracy test as
defined in section 802.3. If the reported uncertainly in the CFM50 is greater
than 10.0%, the airtightness test shall be classified as a Reduced Level of
Accuracy test as defined in section 802.3


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