225 CMR, § 22, ch. 4, § R406 - ENERGY RATING INDEX COMPLIANCE ALTERNATIVE

R406.2 Revise TABLE R406.2 as follows:

TABLE R406.2 REQUIREMENTS FOR ENERGY RATING INDEX

SECTIONa	TITLE
R403.6.1	Heat or Energy Recovery Ventilation
Electrical Power and Lighting Systems
R404.1	Lighting equipment
R404.2	Interior lighting controls
R404.4	Writing for Electric Vehicle Charging Spaces

a. Reference to a code section includes all of the relevant subsections except as indicated in the table.

R406.3 Reserve this section:

R406.3 Building thermal envelope. Reserved.

R406.4 Replace Section with the following:

R406.4 Energy Rating Index. The Energy Rating Index (ERI) shall be the RESNET certified HERS index determined in accordance with ANSI/RESNET/ICC 301. Energy used to recharge or refuel a vehicle used for transportation on roads that are not on the building site shall not be included in the HERS index reference design or the rated design.

R406.5 Revise Section R406.5 and Table R406.5 as follows:

R406.5 ERI-based Compliance. Compliance based on an ERI analysis requires that the rated proposed design and confirmed built dwelling be shown to have a HERS index rating less than or equal to the appropriate value indicated in Table R406.5 when compared to the HERS index reference design for each dwelling unit prior to credit for on-site renewable electric generation.

TABLE R406.5 MAXIMUM ENERGY RATING INDEX

Maximum HERS Index scorea, b
	New construction permits after July 1, 2024	New Construction with R406.5.2 embodied carbon credit	Accessory Dwelling Units	Major alterations, additions, or change of usec
Mixed-Fuel Building	42	45	52	65
Solar Electric Generation	42	45	55	70
All-Electric Building	45	48	55	70
Solar Electric & All-Electric Building	45	48	58	75

^a Maximum HERS rating prior to onsite renewable electric generation in accordance with Section R406.5.

^b The building shall meet the mandatory requirements of Section R406.2.

^c Alterations, Additions or Change of use covered by Section R502.1.1 or R503.1.5 are subject to this maximum HERS rating, except for Historic Buildings which may opt to follow R503.1.1 for alterations.

R406.5.1 Add Subsection R406.5.1 as follows:

R406.5.1 Trade-off for Clean energy systems. New construction following Section R406 or existing buildings and additions following IECC Chapter 5[RE] may use clean energy trade-offs to increase the maximum allowable HERS rating for each unit separately served by any combination of the following:

1. Solar Electric Generation: Solar photovoltaic array rated at 4kW or higher shall offset 3 HERS points for Level 3 alterations, Change of use to Residential R-use categories or for fully attached additions.

2. All-Electric Buildings shall offset 3 HERS points for each dwelling unit in new construction, Level 3 alterations, change of use to Residential R-use categories and fully attached additions.

R406.5.2 Add Subsection R406.5.2 as follows:

R406.5.2 Embodied carbon credit. New construction following Section R406 may use either of the following embodied carbon credits to increase the maximum allowable HERS rating for each unit by 3 HERS points as shown in Table R406.5:

1. Insulation embodied carbon credit: new single dwelling units or R-use buildings containing multiple dwelling units that demonstrate an average calculated insulation Global Warming Potential (GWP) intensity (kg CO2e/m²) less than 0 across the whole building envelope shall offset 3 HERS points for each applicable dwelling unit of new construction. GWP intensity shall be based on the default values in Table R406.5.3, or product specific EPDs or calculations in the approved tools: EC3 and BEAM, may be used in place of default table values.

2. Low GWP concrete mix credit: new single dwelling units or R-use buildings containing multiple dwelling units that demonstrate an average calculated concrete mix Global Warming Potential (GWP) for at least 90% of all concrete mix used in the building of not more than 100% of the 2022 NRMCA NorthEast Benchmark average values shown in Table R406.5.4 shall offset 3 HERS points for each applicable dwelling unit of new construction.

R406.5.3 Add Subsection R406.5.3 as follows:

R406.5.3 Documentation for insulation embodied carbon credit. In order to apply the insulation embodied carbon credit for a new dwelling unit or averaged across a multi-dwelling unit building, the HERS rater of the unit or building must submit a complete calculation to summarize estimated embodied carbon emissions from all insulation materials used in the project. The output metric for this measure shall be Global W arming Potential (GWP) intensity, capturing insulation GWP per conditioned square meter of project area. To complete the basic calculation, project teams shall provide the following information for foundation, floor, wall, and roof insulation materials:

1. Insulation material type

2. Product R-value

3. Total surface area (m²)

4. Default, industry-average GWP value, from Table R406.5.3 or GWP values from Type III Product-specific Environmental Product Declaration (EPD)

5. Total project area (conditioned square feet)

Projects may substitute product-specific data for the default GWP value if the specified product has a lower reported GWP than the default value. Substitution of default GWP values is only allowed when type III product-specific EPDs are sourced and noted. Projects shall use GWP values that include A1-A3 lifecycle stages, as documented in product-specific EPDs, with the exception of SPF and XPS products. For these products, the A5 and B1 values shall be included in the documented GWP value to account for the on-site and off-gassing impact of blowing agents. Projects shall provide the EPDs declaration number in product-specific data substitution.

TABLE R406.5.3 Add Table R406.5.3 as follows:

TABLE R406.5.3 Default Insulation Global Warming Potential Values

All values are from Building Emissions Accounting for Materials (BEAM)^a, unless noted.

Insulation Material	Default Global Warming Potential (GWP) in Kg CO2e/ sq.m. RSI-1
Cellular glass - Aggregate	3.93b
Cellulose - Densepack	-2.00
Cellulose - Blown/loosefill	-0.90
Cork - Board	-4.30
EPS/graphite - Board, unfaced, Type II - 15 psi	2.30
EPS/graphite - Board, unfaced, Type IX - 25 psi	3.10
EPS - Board, unfaced, Type I - 10 psi	2.50
EPS - Board, unfaced, Type II - 15 psi	3.40
EPS - Board, unfaced, Type IX - 25 psi	4.30
Fiberglass - Batt, unfaced	1.00
Fiberglass - Blown/loosefill	1.00
Fiberglass - Blown/spray	1.93c
Hemp - Batt	-0.50
Hemp Crete	-4.10
Mineral wool - Batt, unfaced	1.50
Mineral wool - Blown loose fill	1.90
Mineral wool - Board, unfaced, "light" density	2.70f
Mineral wool - Board, unfaced, "heavy" density	6.90f
Phenolic foam - Board	1.54d
Polyiso - Wall Board	4.10e
Polyiso - Roof Board (GRF facer)	2.11e
Polyiso - Roof Board (CGF facer)	2.95e
SPF - Spray, open cell	1.40
SPF - Spray, closed cell HFO	3.50
SPF - Spray, high density HFO	4.00
SPF - Spray, closed cell HFC	13.10
SPF - Spray, high density HFC	17.00
Straw - Panel	-5.45
Vacuum Insulated Panel
Wood fiber - Board unfaced, European	-4.38
Wood fiber - Board unfaced, North America	-10.30
Wood fiber - Batt, unfaced	-1.60
Wool (Sheep) - Batt	0.20
Wool (Sheep) - Loosefill	0.80
XPS - Board, 25psi HFC	55.50
XPS - Board, 25psi "Low GWP" (HFO/HFC)	5.50

^a https://www.buildersforclimateaction.org/beam-estimator.html

^b EPD Declaration Number

^c EPD Declaration Number

^d EPD Declaration Number EPD-KSI-20190072-IBC1-EN

^e PIMA published ISO-compliant EPDs for polyiso products at:

https://www.polyiso.org/page/EPDs

^f NAIMA value

R406.5.4 Add Subsection R406.5.4, as follows:

R406.5.4 Documentation for low GWP concrete mix credit. In order to apply the low GWP concrete mix credit for one or more new dwelling units, the HERS rater of the unit must submit specific EPDs for concrete used in the unit. Where multiple concrete mixes are used, a complete calculation to summarize estimated embodied carbon emissions from at least 90% of all concrete materials used in the project is required. The output metric for this measure shall be global warming potential (GWP) per cubic meter as supplied, with the EPD verified by the concrete ready-mix provider. The 3 HERS point credit shall be applied when the GWP per cubic meter is demonstrated to be less than the Maximum GWP per cubic meter value shown in Table R406.5.4. for at least 90% of all concrete used for that unit or building as appropriate.

Table R406.5.4 Add Table R406.5.4 as follows:

TABLE R406.5.4 DEFAULT CONCRETE GLOBAL WARMING POTENTIAL VALUES

Maximum GWP (kg CO2e) Limits for Concrete
NORMAL WEIGHT CONCRETE
Specified Compressive Strength (f'c in psi)	Maximum GWP per cubic metera
0-2500	240
2501-3000	264
3001-4000	314
4001-5000	378
5001-6000	399
6001-8000	472
0-3000	517
3001-4000	573
4001-5000	628
aThese numbers are 100% of the Eastern Region average GWP figures from the National Ready Mix Concrete Associations' "A Cradle-to-Gate Life Cycle Assessment of Ready-Mixed Concrete Manufactured by NRMCA Members, Version 3.2," (July 2022), pg. 65. NRMCA LCAReportV3-2 20220224.pdf

R406.6 Revise section R406.6 as follows:

R406.6 Verification by approved agency. Verification of compliance with Section R406 as outlined in Sections R406.4 and R406.5 shall be completed by an approved third-party. Verification of compliance with Section R406.2 shall be completed by the authority having jurisdiction or an approved third-party inspection agency in accordance with Section R105.4.

Notes

225 CMR, § 22, ch. 4, § R406

Adopted by Mass Register Issue 1541, eff. 2/14/2025.