The following comments have been submitted:
Comment #1Page Number: 55Paragraph / Figure / Table / Note: Table 4.3.1(1) Configuration of Index Adjustment DesignComment Intent: Not an ObjectionComment Type: TechnicalComment: When the language was updated for the Air Exchange row within Table 4.2.2(1), the "quadrature" methodology for combining infiltration and mechanical ventilation in the Rated and Reference homes was changed; however, the same change was not made to the Air Exchange row in Table 4.3.1(1), which involves the IAD home. For internal consistency, the same calculation methodology should be applied to the IAD home. Proposed Change: Air exchange rate Combined(a) Infiltration flow rate plus mechanical ventilation flow rate of 0.03 * CFA + 7.5 * (Nbr+1) cfm and with energy loads calculated in quadrature Infiltration flow rate shall be determined using the following envelope leakage rates: 5 ACH50 in IECC[50] Climate Zones 1-2 3 ACH50 in IECC Climate Zones 3-8 (a) Either hourly calculations using the following equation or calculations yielding equivalent results shall be used to determine the combined air exchange rate resulting from Infiltration in combination with the mechanical ventilation. Qi = Qfan,i + Φ Qinf,i where Φ=1 for Balanced Ventilation Systems and otherwise Φ = Qinf,i /( Qinf,i + Qfan,i ) Qi = combined air exchange rate for the time step ‘i’, cfm Qinf,i = Infiltration airflow rate for the time step ‘i’, cfm calculated using Shelter Class 4 Qfan,i = mechanical ventilationVentilation airflow rate for the time step ‘i’, cfm [50] (Normative Note) Climates zones shall be as specified by the 2012 IECC.
When the language was updated for the Air Exchange row within Table 4.2.2(1), the "quadrature" methodology for combining infiltration and mechanical ventilation in the Rated and Reference homes was changed; however, the same change was not made to the Air Exchange row in Table 4.3.1(1), which involves the IAD home.
For internal consistency, the same calculation methodology should be applied to the IAD home.
Air exchange rate
Combined(a) Infiltration flow rate plus mechanical ventilation flow rate of 0.03 * CFA + 7.5 * (Nbr+1) cfm and with energy loads calculated in quadrature
Infiltration flow rate shall be determined using the following envelope leakage rates:
5 ACH50 in IECC[50] Climate Zones 1-2
3 ACH50 in IECC Climate Zones 3-8
[50] (Normative Note) Climates zones shall be as specified by the 2012 IECC.
Comment #2Page Number: 10Paragraph / Figure / Table / Note: Definitions - Occupied SpaceComment Intent: ObjectionComment Type: GeneralComment: The definition for "Occupied Space" has been stricken, but "Occupiable Space" is referenced in the definition for Attached Dwelling Unit. Recommend adjusting the term from "Occupied Space" to "Occupiable Space" and retaining the definition. Proposed Change: Occupiable Space - A room or enclosed space designed for human occupancy in which individuals congregate for amusement, educational or similar purposes or in which occupants are engaged at labor, and which is equipped with means of egress and light and ventilation facilities meeting the requirements of this code.
The definition for "Occupied Space" has been stricken, but "Occupiable Space" is referenced in the definition for Attached Dwelling Unit. Recommend adjusting the term from "Occupied Space" to "Occupiable Space" and retaining the definition.
Occupiable Space - A room or enclosed space designed for human occupancy in which individuals congregate for amusement, educational or similar purposes or in which occupants are engaged at labor, and which is equipped with means of egress and light and ventilation facilities meeting the requirements of this code.
Comment #3Page Number: p25 and p31Paragraph / Figure / Table / Note: Table 4.2.2(1) Specifications for the Energy Rating Reference and Rated HomesComment Intent: ObjectionComment Type: TechnicalComment: It is nonsensical, and a building science failure, to simulate the energy performance of an attached Dwelling-Unit using values obtained from the duct leakage to outside protocol, particularly since the protocol is almost always violated in attached housing (see section 5.2.3 of Std 380-2016, which requires “Any fans that could change the pressure in either the Conditioned Space Volume or any spaces containing ducts or air handlers shall be turned off.”). We know that ducts in apartments are frequently located in the space above the apartment ceiling, and all-too-frequently those spaces lack even visual barriers (let alone air barriers) from adjacent spaces in the building. The pressures in those spaces are routinely impacted by mechanical systems in adjacent units, corridors, and systems shared by multiple dwellings. Those systems can and do skew the results high, or low, rendering the measurement meaningless. In contrast, Total Duct Leakage measurements provide meaningful results, especially if conducted at rough, before the building has multiple mechanical systems running. Furthermore, this draft standard 301-2019 already contains a methodology (in endnote w) for getting reasonably meaningful energy predictions from Total Duct Leakage measurements, by prorating the leakage based the locations of ductwork and air handling equipment. That methodology is the only one that is appropriate for ductwork in attached housing. Proposed Change: Building Component Energy Rating Reference Home Rated Home Thermal distribution systems Thermal Distribution System Efficiency (DSE) of 0.80 shall be applied to both the heating and cooling system efficiencies. For forced air distribution systems: • Detached Dwelling Units shall test duct leakage to outside; • Attached Dwelling Units requiring testing(v) shall test total duct leakage or duct leakage to outside; All duct leakage tests shall be in accordance with requirements of Standard ANSI/RESNET/ICC 380(m) and the energy impacts either calculated through hourly simulation or calculated in accordance with ASHRAE Standard 152 with the ducts located and insulated as in the Rated Home(w). For ductless distribution systems: DSE=1.00 For hydronic distribution systems: DSE=1.00 For untested distribution systems in Attached Dwelling Units: located entirely within Conditioned Space Volume: DSE=0.88 (v) Total duct leakage or duct leakage to outside testing is only required30 for any Attached Dwelling Unit where any portion of the ducts or air handler are located outside of Conditioned Space Volume. Attached Dwelling Units with ducts and air handlers inside the Conditioned Space Volume are permitted to test and use tested duct leakage results in the Rated Home or use the default DSE=0.88.
It is nonsensical, and a building science failure, to simulate the energy performance of an attached Dwelling-Unit using values obtained from the duct leakage to outside protocol, particularly since the protocol is almost always violated in attached housing (see section 5.2.3 of Std 380-2016, which requires “Any fans that could change the pressure in either the Conditioned Space Volume or any spaces containing ducts or air handlers shall be turned off.”).
We know that ducts in apartments are frequently located in the space above the apartment ceiling, and all-too-frequently those spaces lack even visual barriers (let alone air barriers) from adjacent spaces in the building. The pressures in those spaces are routinely impacted by mechanical systems in adjacent units, corridors, and systems shared by multiple dwellings. Those systems can and do skew the results high, or low, rendering the measurement meaningless.
In contrast, Total Duct Leakage measurements provide meaningful results, especially if conducted at rough, before the building has multiple mechanical systems running. Furthermore, this draft standard 301-2019 already contains a methodology (in endnote w) for getting reasonably meaningful energy predictions from Total Duct Leakage measurements, by prorating the leakage based the locations of ductwork and air handling equipment. That methodology is the only one that is appropriate for ductwork in attached housing.
Building Component
Energy Rating Reference Home
Rated Home
Thermal distribution systems
Thermal Distribution System Efficiency (DSE) of 0.80 shall be applied to both the heating and cooling system efficiencies.
For forced air distribution systems:
• Detached Dwelling Units shall test duct leakage to outside;
• Attached Dwelling Units requiring testing(v) shall test total duct leakage or duct leakage to outside;
All duct leakage tests shall be in accordance with requirements of Standard ANSI/RESNET/ICC 380(m) and the energy impacts either calculated through hourly simulation or calculated in accordance with ASHRAE Standard 152 with the ducts located and insulated as in the Rated Home(w).
For ductless distribution systems: DSE=1.00
For hydronic distribution systems: DSE=1.00
For untested distribution systems in Attached Dwelling Units: located entirely within Conditioned Space Volume: DSE=0.88
(v) Total duct leakage or duct leakage to outside testing is only required30 for any Attached Dwelling Unit where any portion of the ducts or air handler are located outside of Conditioned Space Volume. Attached Dwelling Units with ducts and air handlers inside the Conditioned Space Volume are permitted to test and use tested duct leakage results in the Rated Home or use the default DSE=0.88.
Comment #4Page Number: 22-23Paragraph / Figure / Table / Note: Table 4.2.2(1) Specifications for the Energy Rating Reference and Rated HomesComment Intent: ObjectionComment Type: TechnicalComment: I have two distinct edits within this section. In the absence of my first edit below, the existing language wipes out the Compartmentalization benefit for all interior units, not just the ones employing an exhaust-only mechanical ventilation strategy. This is contrary to the original intent, which was simply to limit the benefits for exhaust-only ventilation when less than half of the ventilation air was coming from outdoors. My second edit seeks to clarify language so as to avoid ongoing confusion between total air exchange rate and Dwelling-Unit mechanical ventilation. Prior to my edit, the language was confusing enough to perpetuate misconceptions that the equation “0.03 x CFA + 7.5 x (Nbr+1) cfm” is the required mechanical ventilation, rather than the required total air exchange. Proposed Change: Building Component Energy Rating Reference Home Rated Home Air exchange rate Specific Leakage Area (SLA) (d) = 0.00036 assuming no energy recovery, supplemented as necessary to achieve the required Dwelling-Unit total air exchange rate (Qtot).(f), (g) In accordance with Standard ANSI/RESNET/ICC 380, obtain airtightness test results for: • Building enclosure (for Detached Dwelling Units) • Compartmentalization Boundary (for Attached Dwelling Units). For Attached Dwelling Units with airtightness test results ≤ 0.30 cfm50 per ft2 of Compartmentalization Boundary, the test results shall be multiplied by reduction factor Aext (r) to determine the Infiltration rate. For Attached Dwelling Units with airtightness test results > 0.30 cfm50 per ft2 of Compartmentalization Boundary, the test results shall be modeled as the Infiltration rate. For residences without Dwelling-Unit Mechanical Ventilation Systems, or without measured airflow, or where Aext (r) < 0.5 and the Mechanical Ventilation System is solely an Exhaust System, the Infiltration rate (e) shall be as determined above, but not less than 0.30 ACH. For residences with Dwelling-Unit Mechanical Ventilation Systems, the total air exchange rate shall be the Infiltration rate (e) as determined above, in combination (g) with the time-averaged Dwelling-Unit Mechanical Ventilation System rate,(f), (t) which shall be the value measured in accordance with Standard ANSI/RESNET/ICC 380, but. The Dwelling-Unit Mechanical Ventilation System rate shall be increased as needed to ensure that the total air exchange rate is no less than Qtot = 0.03 x CFA + 7.5 x (Nbr+1) cfm.
I have two distinct edits within this section.
In the absence of my first edit below, the existing language wipes out the Compartmentalization benefit for all interior units, not just the ones employing an exhaust-only mechanical ventilation strategy. This is contrary to the original intent, which was simply to limit the benefits for exhaust-only ventilation when less than half of the ventilation air was coming from outdoors.
My second edit seeks to clarify language so as to avoid ongoing confusion between total air exchange rate and Dwelling-Unit mechanical ventilation. Prior to my edit, the language was confusing enough to perpetuate misconceptions that the equation “0.03 x CFA + 7.5 x (Nbr+1) cfm” is the required mechanical ventilation, rather than the required total air exchange.
Specific Leakage Area (SLA) (d) = 0.00036 assuming no energy recovery, supplemented as necessary to achieve the required Dwelling-Unit total air exchange rate (Qtot).(f), (g)
In accordance with Standard ANSI/RESNET/ICC 380, obtain airtightness test results for:
• Building enclosure (for Detached Dwelling Units)
• Compartmentalization Boundary (for Attached Dwelling Units).
For Attached Dwelling Units with airtightness test results ≤ 0.30 cfm50 per ft2 of Compartmentalization Boundary, the test results shall be multiplied by reduction factor Aext (r) to determine the Infiltration rate. For Attached Dwelling Units with airtightness test results > 0.30 cfm50 per ft2 of Compartmentalization Boundary, the test results shall be modeled as the Infiltration rate.
For residences without Dwelling-Unit Mechanical Ventilation Systems, or without measured airflow, or where Aext (r) < 0.5 and the Mechanical Ventilation System is solely an Exhaust System, the Infiltration rate (e) shall be as determined above, but not less than 0.30 ACH.
For residences with Dwelling-Unit Mechanical Ventilation Systems, the total air exchange rate shall be the Infiltration rate (e) as determined above, in combination (g) with the time-averaged Dwelling-Unit Mechanical Ventilation System rate,(f), (t) which shall be the value measured in accordance with Standard ANSI/RESNET/ICC 380, but. The Dwelling-Unit Mechanical Ventilation System rate shall be increased as needed to ensure that the total air exchange rate is no less than Qtot = 0.03 x CFA + 7.5 x (Nbr+1) cfm.