303 Technical Requirements

HERS Update to Standard ANSI/RESNET/ICC 301-2019

MINHERS Addendum 42 adopted Standard ANSI/RESNET/ICC 301-2019 to replace Standard ANSI/RESNET/ICC 301-2014 as the basis for calculation of the HERS rating. Addendum 42 currently allows voluntary use of RESNET accredited software based on Standard 301-2019 and will require use of Standard 301-2019 on January 1, 2022. See the section 502.3.2 definition for Mandatory Compliance Date.

303.1 Applicable Standards

All RESNET Home Energy Ratings conducted in accordance with this Standard shall comply with the provisions of ANSI/RESNET/ICC 301, “Standard for the Calculation and Labeling of the Energy Performance of Dwelling and Sleeping Units using an Energy Rating Index.”

Exception 1: RESNET Home Energy Ratings conducted in Puerto Rico and the US Virgin Islands shall comply with the provisions of ANSI/RESNET/ICC 301, except that Ratings of homes with a permit date prior to January 1, 2024 are permitted to use a default infiltration rate of 10 ACH50 in lieu of conducting an airtightness test in accordance with Standard ANSI/RESNET/ICC 380. In addition, for a home in the Tropical Climate Zone for which its Living Space is not serviced by a space heating mechanical system and not more than one-half of its Living Space is serviced by a space cooling mechanical system, the Conditioned Space Volume shall be defined as the volume of its Living Space and the Conditioned Floor Area shall be defined as the floor area of its Living Space.

Exception 2: RESNET Home Energy Ratings shall comply with the requirements of ANSI/RESNET/ICC 301and its Addenda except that Ratings on homes with a building permit date, or alternate pursuant to Addendum 43, prior to January 1, 2021 are permitted to use the following exception:

When the following condition is met and documented, duct leakage testing is not required.

At a pre-drywall stage of construction, 100% of the distribution system and air handler shall be visible and visually verified to be contained inside the Conditioned Space Volume. At a final stage of construction, ductwork that is visible and the air handler shall again be verified to be contained in the Conditioned Space Volume.

To calculate the energy impacts on the Rated Home, a DSE of 0.88 shall be applied to both the heating and cooling system efficiencies.

Exception 3: RESNET Home Energy Ratings conducted on Dwelling and Sleeping Units in multifamily buildings over three stories in height shall comply with one of the following as determined by the Mandatory Compliance Date requirements for ANSI/RESNET/ICC 301-2019 and this section,
a) ANSI/RESNET/ICC 301-2014 and ANSI/RESNET/ICC 380-2016 and their addenda and with RESNET’s Guidelines for Multifamily Energy Ratings, or
b) ANSI/RESNET/ICC 301-2019 and ANSI/RESNET/ICC 380-2019 and their addenda
(Note: Option a) applies only if the building permit was issued prior to January 1, 2022, otherwise HERS ratings must comply with option b).)

Exception 4: RESNET Home Energy Ratings shall be calculated using the modifications of Standards ANSI/RESNET/ICC 301-2019 and ANSI/RESNET/ACCA/ICC 310-2020 established by Addendum 53f. (See Addendum 53f).

Exception 5: The field inspection and testing sampling requirements in the RESNET Guidelines for Multifamily Energy Ratings (consecutive sections titled "Sample Set of Multifamily Dwelling Units" through "Quality Assurance by Multifamily Sampling Providers") are authorized for Sampled Ratings of Dwelling Units and Sleeping Units in multifamily buildings until the MINHERS Chapter 6 or other RESNET standard is updated to include sampling requirements specific to multifamily buildings.

Exception 6: RESNET Home Energy Ratings shall comply with the requirements of ANSI/RESNET/ICC 301 and its Addenda except Home Energy Ratings shall be calculated using the modifications of Standard ANSI/RESNET/ICC 301-2019 as follows:
Heating Seasonal Performance Factor 2 (HSPF2) – A standardized measure of Heat Pump efficiency, based on the total heating output of a Heat Pump in Btu and divided by the total electric energy input in watt-hours and under test conditions specified by the Air Conditioning and Refrigeration Institute Standard 210/240 2023.

Seasonal Energy Efficiency Ratio 2 (SEER2) – A standardized measure of Air Conditioner efficiency based on the total cooling output of an Air Conditioner in Btu/h, divided by the total electric energy input, in Watt-hours, under test conditions specified by the Air Conditioning and Refrigeration Institute Standard 210/240 2023.

4.4.4. Air Source Heat Pumps and Air Conditioners.

4.4.4.1. For Heat Pumps and Air Conditioners where a detailed, hourly HVAC simulation is used to separately model the compressor and evaporator energy (including part-load performance), the back-up heating energy, the distribution fan or blower energy and crank case heating energy, the Manufacturer’s Equipment Performance Rating (HSPF and SEER¹) shall be modified to represent the performance of the compressor and evaporator components alone.² The energy uses of all components, including compressor and distribution fan/blower and crank case heater, shall then be added together to obtain the total energy uses for heating and cooling.

For Heat Pumps and Air Conditioners with the more recent Manufacturer’s Equipment Performance Ratings (HSPF2 or SEER2) available, and HSPF or SEER are not available, these ratings shall be converted to HSPF and SEER values by dividing HSPF2 or SEER2 by the conversion factors in Table 4.4.4.1(1). If the type of equipment is not determined, the conversion shall default to the “Ducted Split System” factors. All calculations, including Equation 4.1-1a, shall use HSPF or SEER values as made available by the Manufacturer or converted as specified in this section.

Table 4.4.4.1(1) SEER2 and HSPF2 Conversion Factors³

^{1(Normative Note) For Commercial Variable Refrigerant Flow (VRF) Multi-Split Air Conditioning and Heat Pump Equipment, use IEER in place of SEER.
2 (Informative Note) Such approaches are described in Cutler et al. 2011 and Fairey et al. 2004.
3 (Informative Note) Conversion factors developed by AHRI, and adopted by RESNET.
4 EER and EER2 are not required in this Standard for equipment relevant to this table, but the values are shared here for informative purposes.
5(Normative Note) Space Constrained AC or Heat Pump – A space constrained unit is a product that has two overall exterior dimensions or an overall displacement that is substantially smaller than those of other units that are of similar heating and/or cooling capacity, and has rated cooling capacities no greater than 30,000 BTU/hr., and that if increased, would result in considerable increase in cost of installation or utility, and was available for purchase in the United States as of December 1, 2000. (Aligns with Title 20 and AHRI Standard 210/240 definitions.)}

Exception 7: RESNET Home Energy Ratings shall be calculated using the modifications of Standards ANSI/RESNET/ICC 301-2019 established by Addendum 66 and Addendum 79.

303.2 Rating Registration

All Confirmed, Threshold and Sampled HERS Ratings shall be registered with the National RESNET Registry in accordance with Sections 102.1.4.10 and 102.1.4.12.

303.3 HERS Rating Tools

All RESNET-accredited HERS Rating Tools shall prohibit printing of Confirmed, Threshold and Sampled HERS Ratings until such rating has been registered with the National RESNET Registry and a unique registration identification has been assigned. Said registration identification shall be prominently displayed on all printed HERS Rating reports.