Comment #1Amendment: Proposed MINHERS Addendum 39, Mechanical Ventilation Airflow and Fan Wattage, Draft PDS-01Page Number: 2Paragraph / Figure / Table / Note: Exception 3Comment Intent: ObjectionComment Type: TechnicalComment: As currently drafted, the first sentence of the proposed amendment reads "Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Infiltration rate in the Rated Home shall be no less than 0.3 ACH." (emphasis added). Shouldn't this be the Mechanical Ventilation Rate? Proposed Change: Exception 3: Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Mechanical Ventilation RateInfiltration rate in the Rated Home shall be no less than 0.3 ACH. To determine fan energy in the Rated Home, ventilation fan watts shall be based on the table below for the given system or the value observed in the Rated Home, for the highest airflow setting. Where needed to calculate fan watts, for systems other than Central Fan Integrated Supply (CFIS), the Whole-House Mechanical Ventilation System rate shall be assumed to be equal to Qfan, as calculated in accordance with Section 4.1.2 of ASHRAE Standard 62.2. For CFIS systems, the cfm used to determine fan watts shall be the larger of 400 cfm per 12 kBtu/h cooling capacity or 240 cfm per 12 kBtu/h heating capacity.
As currently drafted, the first sentence of the proposed amendment reads "Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Infiltration rate in the Rated Home shall be no less than 0.3 ACH." (emphasis added).
Shouldn't this be the Mechanical Ventilation Rate?
Exception 3: Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Mechanical Ventilation RateInfiltration rate in the Rated Home shall be no less than 0.3 ACH. To determine fan energy in the Rated Home, ventilation fan watts shall be based on the table below for the given system or the value observed in the Rated Home, for the highest airflow setting. Where needed to calculate fan watts, for systems other than Central Fan Integrated Supply (CFIS), the Whole-House Mechanical Ventilation System rate shall be assumed to be equal to Qfan, as calculated in accordance with Section 4.1.2 of ASHRAE Standard 62.2. For CFIS systems, the cfm used to determine fan watts shall be the larger of 400 cfm per 12 kBtu/h cooling capacity or 240 cfm per 12 kBtu/h heating capacity.
Comment #2Amendment: Proposed MINHERS Addendum 39, Mechanical Ventilation Airflow and Fan Wattage, Draft PDS-01Page Number: 303.1 Applicable StandardsParagraph / Figure / Table / Note: 303.1 Applicable StandardsComment Intent: ObjectionComment Type: TechnicalComment: I agree in principle with this proposal, but have a few recommendations for changes to better coordinate with the IECC and with ASHRAE 62.2. Thanks for your work, Gayathri! Proposed Change: Recommend modifying the proposed change as follows: Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Effective Annual Average Infiltration Rrate in the Rated Home shall be no less than 0.3 ACH as calculated using Equation 4.3 of ASHRAE 62.2.... ASHRAE Standard 62.2-20136, “Ventilation and Acceptable Indoor Air Quality inLow-Rise Residential Buildings”, ASHRAE, Atlanta, GA [Note: 62.2-2013 does not have a formula for calculating the Effective Annual Average Infiltration Rate, so the 2016 version would need to be referenced for accuracy.] Recommend using the following values for W/cfm within the table provided: Exhaust: change to 0.7 (based on 2018 IECC minimum for exhaust fan) Supply: retain at 0.35 (based on 2018 IECC minimum for in-line fan) Balanced: change to 0.85 (based on 2018 IECC minimum for H/ERV) H/ERV fans: change to 0.85 (based on 2018 IECC minimum for H/ERV) CFIS fans: retain at 0.5 (similar to field-tested values reported in Home Energy article; https://buildingscience.com/documents/published-articles/pa-ecm-eficiency/view) Range hoods: change to 0.35 (based on IECC minimum for range hoods) Note: W/cfm values for the reference home may also need to be updated elsewhere in the standard to reflect these recommended defaults.
I agree in principle with this proposal, but have a few recommendations for changes to better coordinate with the IECC and with ASHRAE 62.2. Thanks for your work, Gayathri!
Recommend modifying the proposed change as follows:
Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Effective Annual Average Infiltration Rrate in the Rated Home shall be no less than 0.3 ACH as calculated using Equation 4.3 of ASHRAE 62.2....
ASHRAE Standard 62.2-20136, “Ventilation and Acceptable Indoor Air Quality inLow-Rise Residential Buildings”, ASHRAE, Atlanta, GA [Note: 62.2-2013 does not have a formula for calculating the Effective Annual Average Infiltration Rate, so the 2016 version would need to be referenced for accuracy.]
Recommend using the following values for W/cfm within the table provided:
Exhaust: change to 0.7 (based on 2018 IECC minimum for exhaust fan)
Supply: retain at 0.35 (based on 2018 IECC minimum for in-line fan)
Balanced: change to 0.85 (based on 2018 IECC minimum for H/ERV)
H/ERV fans: change to 0.85 (based on 2018 IECC minimum for H/ERV)
CFIS fans: retain at 0.5 (similar to field-tested values reported in Home Energy article; https://buildingscience.com/documents/published-articles/pa-ecm-eficiency/view)
Range hoods: change to 0.35 (based on IECC minimum for range hoods)
Note: W/cfm values for the reference home may also need to be updated elsewhere in the standard to reflect these recommended defaults.
Comment #3Amendment: Proposed MINHERS Addendum 39, Mechanical Ventilation Airflow and Fan Wattage, Draft PDS-01Page Number: 1Comment Intent: Not an ObjectionComment Type: EditorialComment: Two comments/questions stemming from the Background/Rationale: There are many situations where ventilation airflows cannot be measured. 1) Will the examples of situations where ventilation airflow cannot be measured provided, or will RESNET leave it to the Rater to determine? The 2019 version of 301 has provided an avenue for an energy rating to be completed, in the absence of measured ventilation airflow, in which it simply treats the Rated Home the same as a home without a mechanical ventilation system. 2) What 'avenue' is this refering to? A Rated Home without a mechanical ventilation system has a Reference Home without mechanical ventilation. If that is actually being proposed in the 2019 draft of 301, then why not just apply this now?
Two comments/questions stemming from the Background/Rationale:
There are many situations where ventilation airflows cannot be measured.
1) Will the examples of situations where ventilation airflow cannot be measured provided, or will RESNET leave it to the Rater to determine?
The 2019 version of 301 has provided an avenue for an energy rating to be completed, in the absence of measured ventilation airflow, in which it simply treats the Rated Home the same as a home without a mechanical ventilation system.
2) What 'avenue' is this refering to? A Rated Home without a mechanical ventilation system has a Reference Home without mechanical ventilation. If that is actually being proposed in the 2019 draft of 301, then why not just apply this now?
Comment #4Amendment: Proposed MINHERS Addendum 39, Mechanical Ventilation Airflow and Fan Wattage, Draft PDS-01Page Number: 2Paragraph / Figure / Table / Note: Addendum 39-201x, Exception 3Comment Intent: ObjectionComment Type: TechnicalComment: Thank you for your attention to this matter. I think the logic in Exception 3 and the corresponding table offers a reasonable default for the infiltration calc and electric usage. However I think we should allow a rater to use the highest rated fan wattage from the manufacturer's spec sheet if that is lower than the value obtained when using the default table. Fan manufacturers are supplying more info with their newer products these days and it is not hard to find a table in a pdf online that will show the high and low flow limits and the corresponding static pressures and watt draws. I think it is reasonable for a rater to use the high end watt draw IF they are not measuring the watt draw with an multimeter or if they are not measuring the Static Pressure and extrapolating the watt draw (which is currently excepted in the industry as a way to approximate watt usage if comparing with manufacturer's chart or graph). Proposed Change: Exception 3: Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Infiltration rate in the Rated Home shall be no less than 0.3 ACH. To determine fan energy in the Rated Home, ventilation fan watts shall be: a) based on the table below for the given system or OR b) the value observed in the Rated Home, for the highest airflow setting, OR c) the highest reported watt usage from the equipment manufacturer’s specifications sheet. Where needed to calculate fan watts, for systems other than Central Fan Integrated Supply (CFIS), the Whole-House Mechanical Ventilation System rate shall be assumed to be equal to Qfan, as calculated in accordance with Section 4.1.2 of ASHRAE Standard 62.2. For CFIS systems, the cfm used to determine fan watts shall be the larger of 400 cfm per 12 kBtu/h cooling capacity or 240 cfm per 12 kBtu/h heating capacity.
Thank you for your attention to this matter.
I think the logic in Exception 3 and the corresponding table offers a reasonable default for the infiltration calc and electric usage. However I think we should allow a rater to use the highest rated fan wattage from the manufacturer's spec sheet if that is lower than the value obtained when using the default table. Fan manufacturers are supplying more info with their newer products these days and it is not hard to find a table in a pdf online that will show the high and low flow limits and the corresponding static pressures and watt draws. I think it is reasonable for a rater to use the high end watt draw IF they are not measuring the watt draw with an multimeter or if they are not measuring the Static Pressure and extrapolating the watt draw (which is currently excepted in the industry as a way to approximate watt usage if comparing with manufacturer's chart or graph).
Exception 3: Where Whole-House Mechanical Ventilation System airflow rate cannot be measured, the Infiltration rate in the Rated Home shall be no less than 0.3 ACH. To determine fan energy in the Rated Home, ventilation fan watts shall be: a) based on the table below for the given system or OR b) the value observed in the Rated Home, for the highest airflow setting, OR c) the highest reported watt usage from the equipment manufacturer’s specifications sheet. Where needed to calculate fan watts, for systems other than Central Fan Integrated Supply (CFIS), the Whole-House Mechanical Ventilation System rate shall be assumed to be equal to Qfan, as calculated in accordance with Section 4.1.2 of ASHRAE Standard 62.2. For CFIS systems, the cfm used to determine fan watts shall be the larger of 400 cfm per 12 kBtu/h cooling capacity or 240 cfm per 12 kBtu/h heating capacity.
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