225 CMR 23.00 — Massachusetts Stretch Code and specialized code for commercial, multi-family and all other construction - 2025 amendments to IECC2021 and ASHRAE standards 90.1-2019

23.00 Massachusetts Stretch Code and specialized code for commercial, multi-family and all other construction - 2025 amendments to IECC2021 and ASHRAE standards 90.1-2019

225 CMR: DEPARTMENT OF ENERGY RESOURCES 225 CMR 23.00: MASSACHUSETTS STRETCH CODE AND SPECIALIZED CODE FOR COMMERCIAL, MULTI-FAMILY AND ALL OTHER CONSTRUCTION - 2025 AMENDMENTS TO IECC2021 AND ASHRAE STANDARD 90.1-2019 (Note: please see 225 CMR 22.00 for Residential Low-rise construction) Chapter 1: [CE] SCOPE AND ADMINISTRATION SECTION C103 - CONSTRUCTION DOCUMENTS C103.2 Revise and insert into Section C103.2 as follows: C103.2 (2) Replace C103.2(2) as follows: 2. For buildings greater than 20,000-sf, backstop compliance and thermal bridge derating calculations performed in accordance with latest edition of Massachusetts Stretch Energy Code Technical Guidance, Attachment A, Envelope Performance and Thermal Bridge Derating. For buildings up to 20,000-sf, envelope information in COMcheck submittal per Section C103.2.2. Exception: Buildings following either of the Certified Performance Standard Compliance pathways in Section C401.2.2 (Passive House or HERS Compliance). In the case of buildings over 20,000-sf which are showing compliance with C401.2.2 for only a portion of the building, this exception does not apply to the portion of the building which is not showing compliance with Section C401.2.2. C103.2 Insert the following after Subsection C103.2(13): 14. Solar Ready roof zone in accordance with Appendix CB, or Potential Solar Zone Area in accordance with Appendix CC. 15. EV Ready Spaces locations in accordance with Section C405.13. 16. For buildings using the Relative Performance Pathway (C407.2) because average ventilation at full occupancy is greater than 0.5 cfm/sf, submit mechanical equipment schedules for all new and/or existing air handling equipment designed to supply any quantity of outdoor air to the space, and an airflow riser diagram encompassing the complete project boundary. Mechanical equipment schedules shall clearly indicate the total design outdoor airflow for each unit. The air riser diagram shall include all supply, exhaust, and return air systems serving the space. The air riser diagram shall also include a summary of the total outdoor air supplied, the total gross square footage served by the ventilation system, and the overall flow rate per area in cfm/sf. 17. For mixed fuel building following Appendix CC, construction documents showing electric HVAC retrofit design prepared by the HVAC engineer. The contract documents shall show future replacement of combustion equipment based HVAC system with an equivalent all electric system. Contract documents shall show combustion equipment to be replaced, future electric equipment, supporting electric, structural, and architectural infrastructure to be installed during building construction, and space allotments for future equipment. 18. District Energy System Order of Conditions issued by the Department of Energy Resources (DOER), if applicable. C103.2.2 Add the following Subsection: C103.2.2 COMcheck Submittal Simulation Guidelines.

1. For buildings up to 20,000-sf, the construction documents submitted with the application for permit shall be accompanied by completed COMcheck Envelope, Lighting and Mechanical Compliance Certificates, and a Plan Review Inspection Checklist for the purposes of demonstrating compliance with the energy provisions of 225 CMR 23.00: Stretch Energy Code.
2. For buildings greater than 20,000-sf, the construction documents submitted with the application for permit shall be accompanied by completed COMcheck Lighting and Mechanical Compliance Certificates, and a Plan Review Inspection Checklist. 2/14/25 225 CMR - 237 (Mass. Register #1541, 2/14/2025)

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued 3. For buildings greater than 20,000-sf which are following C401.2.1 Part 3, Relative Performance Compliance, the construction documents submitted with the application for permit shall be accompanied with completed calculations performed in accordance with latest edition of Massachusetts Stretch Energy Code Technical Guidance, Attachment B, ASHRAE Appendix G Relative Performance Simulation Guidelines. 4. For buildings greater than 20,000-sf which are following C401.2.1 Part 2, Targeted Performance Compliance, the construction documents submitted with the application for permit shall be accompanied with completed calculations performed in accordance with latest edition of Massachusetts Stretch Energy Code Technical Guidance, Attachment C, Targeted Performance Simulation Guidelines. Exception: Buildings documenting compliance following either of the C401.2.2 Certified Performance Standard Compliance pathways (Passive House or HERS Compliance) shall follow applicable reporting requirements detailed Section C407. In the case of buildings over 20,000-sf which are showing compliance with C401.2.2 for only a portion of the building, this exception does not apply to the portion of the building which is not showing compliance with Section C401.2.2. Chapter 2: [CE] DEFINITIONS SECTION C202 GENERAL DEFINITIONS C202 Add the following definitions: ALL-ELECTRIC BUILDING. A building with no on-site combustion equipment for fossil fuel use or capacity for including fossil fuel use in space heating, water heating, cooking, or drying appliances. AUTOMATIC LOAD MANAGEMENT SYSTEMS (ALMS). A control system that allows multiple connected electric vehicle supply equipment (EVSE) to share a circuit or panel and automatically manage power at each charger, reducing the total connected electrical capacity of all EVSE. CLASS 3 EXHAUST. Exhaust meeting the definition of Class 3 air in ASHRAE/ASHE Standard 62.1-2019, including air with significant contaminant concentration, significant sensory-irritation intensity, or offensive odor. The Class 3 Exhaust system must be capable of reducing exhaust and makeup airflow rates to 50% of the zone design values or the minimum required to maintain pressurization relationship requirements. CLASS 4 EXHAUST. Exhaust meeting the definition of Class 4 air in ASHRAE/ASHE Standard 62.1-2019, including laboratory fume hood exhaust, exhaust where energy recovery is not allowed by ASHRAE/ASHE Standard 170 for use in energy recovery systems with leakage potential, and systems exhausting toxic, flammable, paint or corrosive fumes or dust. The Class 4 Exhaust system must be capable of reducing exhaust and makeup airflow rates to 50% of the zone design values or the minimum required to maintain pressurization relationship requirements. Excludes exempt exhaust. CLEAN BIOMASS HEATING SYSTEM. Wood-pellet fired central boilers and furnaces with less than 3 million Btu/hour rated heat input, where the equipment has a thermal efficiency rating of 85% (higher heating value) or greater; and a particulate matter emissions rating of no more than 0.08 lb. PM 2.5 /MMBtu heat output, or wood chip fired central boilers and furnaces with less than 3 million Btu/hour rated heat input, where the equipment has a thermal efficiency rating of 80% or greater and a particulate matter emissions rating of no more than 0.10 lb. PM 2.5 /MMBtu heat output. COMBUSTION EQUIPMENT. Any equipment or appliance used for space heating, service water heating, cooking, clothes drying and/or lighting that can use fuel gas, fuel oil or solid fuel and that is not a clean biomass heating system. DEDICATED OUTSIDE AIR SYSTEM (DOAS). A ventilation system that supplies 100 percent outdoor air primarily for the purpose of ventilation and that is a separate system from the zone space-conditioning system. 2/14/25 225 CMR - 238

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued DISTRICT ENERGY SYSTEM. A system for transferring heat energy from a centralized location to a distributed network of buildings through a system of pipes for the purposes of building space heating and/or space cooling and/or service water heating. DISTRICT ENERGY SYSTEM, HEAT RECOVERY ENABLED. A district energy system capable of recovering excess heat energy from buildings on the distributed network which are in cooling mode for useful space and/or service water heating in other buildings on the network. DISTRICT ENERGY SYSTEM ORDER OF CONDITIONS. A document issued by the Commonwealth of Massachusetts Department of Energy Resources which regulates the decarbonization and efficient electrification of all energy inputs of a district energy system for the purposes of building energy code compliance. EFFICIENT ELECTRIFICATION. Space heating using equipment having a system efficiency and a coefficient of performance greater than one (100%) at outdoor design temperature or water heating equipment with a system efficiency or Uniform Energy Factor (UEF) of greater than two (200%) at indoor operating temperature. ELECTRIC VEHICLE. An automotive-type vehicle for on-road use, such as passenger automobiles, buses, trucks, vans, neighborhood electric vehicles, electric motorcycles, and the like, primarily powered by an electric motor that draws current from a rechargeable storage battery, fuel cell, photovoltaic array, or other source of electric current. Informational note: defined as in 527 CMR 12 section 625.2. ELECTRIC VEHICLE SUPPLY EQUIPMENT (EVSE). The conductors, including the ungrounded, grounded, and equipment grounding conductors, and the electric vehicle connectors, attachment plugs, and all other fittings, devices, power outlets, or apparatus installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle. Informational note: defined as in 527 CMR 12 section 625.2. ELECTRIC VEHICLE READY PARKING SPACE (“EV READY SPACE”). A designated parking space which is provided with wiring and electrical service sufficient to provide AC Level or equivalent EV charging, as defined by Standard SAE J1772 or SAE J3400 for EVSE servicing light duty electric vehicles. ENTHALPY RECOVERY RATIO. The ratio of change in enthalpy of the entering supply airflow and the leaving supply airflow to the difference in enthalpy between the entering supply airflow and the entering exhaust airflow, with no adjustment to account for that portion of the psychrometric change in the leaving supply airflow that is the result of leakage of entering exhaust airflow rather than exchange of heat or moisture between the airstreams. EXEMPT EXHAUST. Exhaust for which energy recovery systems are prohibited by the applicable International Mechanical Code. EXHAUST SOURCE HEAT PUMP. A type of electric heat pump that utilizes ventilation exhaust air as the thermal energy source. FUEL GAS. A natural gas, manufactured gas, liquified petroleum gas or a mixture of these. Informational note: Definition of fuel gas is mirrored from 2021 IMC to be useful in defining combustion equipment. It typically refers to natural gas and propane. FUEL OIL. Kerosene or any hydrocarbon oil having a flash point not less than 100EF (38EC). Informational note: Definition of fuel oil is mirrored from 2021 IMC to be useful in defining combustion equipment. It typically refers to heating oil products. GLAZED WALL SYSTEM. System consisting of any combination of both vision glass and/or spandrel sections to create an above-grade wall that is designed to separate the exterior and interior environments. These systems include, but are not limited to, curtain walls, window walls, and storefront windows. 2/14/25 225 CMR - 239

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued MIXED-FUEL BUILDING. A building that contains combustion equipment or includes piping for such equipment. OTHER EXHAUST. Any exhaust that does not fall under the categories of Exempt Exhaust, Class 4 Exhaust, or Class 3 Exhaust. SENSIBLE ENERGY RECOVERY RATIO. The change in the dry-bulb temperature of the outdoor air supply divided by the difference between the outdoor air and entering exhaust air dry-bulb temperatures, expressed as a percentage. SENSIBLE RECOVERY EFFICIENCY. The net sensible energy recovered by the supply airstream as adjusted by any supply fan energy, energy consumption of other equipment transferring heat to/from the supply airstream, case heat loss or heat gain, air leakage, airflow mass imbalance between the two airstreams, and the energy used for defrost, as a percent of the sum of the potential sensible energy that could be recovered from ambient conditions, the exhaust fan energy, and the energy consumption of any other equipment transferring heat to/from the exhaust airstream. SPANDREL SECTION. The opaque portion of a glazed wall system typically used to conceal or obscure features of the building structure or used for visual effect. A spandrel section may consist of, but is not limited to, an exterior exposed cladding layer (glazing or opaque material) with an interior insulated panel. TENANT SPACE FIT OUT ZONE. Portion of a building in which only the envelope is completed, and the mechanical, lighting, and other interior systems are either incomplete or partially complete at the time of building permitting. Mechanical, lighting, and other interior systems may be completed under either the same building permit or a different building permit from the host building. THERMAL BRIDGE: Part of the building envelope where otherwise uniform thermal resistance is changed by full or partial penetration of the thermal insulation by materials with higher thermal conductivities and/or where the interior and exterior areas of the envelope are different, such as, but not limited to, parapets and corners. CLEAR FIELD: A thermal bridge that is uniformly distributed throughout an assembly such that accounting for the thermal bridge individually is impractical for whole-building calculations. LINEAR: A thermal bridge that is continuous in one direction of the exterior envelope. POINT A thermal bridge that is discrete and countable on an individual basis for whole-building calculations. TOTAL RECOVERY EFFICIENCY: The net total energy (sensible plus latent) recovered by the supply airstream as adjusted by supply fan energy, energy consumption of another equipment transferring heat to/from the supply airstream, case heat loss or heat gain, air leakage, airflow mass imbalance between the two airstreams, and the energy use for defrost as a percent of the sum of potential energy that could be recovered from the ambient conditions, the exhaust fan energy, and the energy consumption of any other equipment transferring heat to/from the exhaust airstream. Chapter 3: [CE] GENERAL REQUIREMENTS SECTION C301 CLIMATE ZONES C301 Abbreviate Section C301 as follows: C301.1 General. Massachusetts is in climate zone 5A. 2/14/25 225 CMR - 240

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Chapter 4: [CE] COMMERCIAL ENERGY EFFICIENCY SECTION C401 GENERAL C401.2 Replace Section C401.2 as follows: C401.2 Application. Commercial buildings shall comply with either Section C401.2.1 or C401.2.2. When constructed for the first time, all requirements imposed on the building housing a tenant space fit out zone shall also apply to the tenant space fit out zone. Commercial buildings containing multiple use type classifications (mixed-use buildings) shall comply with C401.2.4. C401.2.1 Prescriptive and Performance Compliance. Commercial buildings shall comply with one of the following:

1. Prescriptive Compliance: This pathway may only be used for any nonresidential building, or portions thereof when following C401.2.4, up to 20,000-sf. The Prescriptive Compliance pathway requires compliance with Sections C401.3, C402 through C406, and Section C408.
2. Targeted Performance Compliance: This pathway shall be used for dormitory, fire station, library, office, school, police station, post office, and town hall buildings, or portions thereof when following C401.2.4, over 20,000-sf which have average ventilation at full occupancy of 0.5 cfm/sf or less. This pathway can also be used for any building of any size. After 1 July 2024, this pathway shall be used for residential buildings, or portions thereof when following C401.2.4, over 12,000-sf, or the building may comply with Section C401.2.2. The Targeted Performance Compliance pathway requires compliance with Section C401.3, Sections C402 through C406, Section C407.1, Section 408, and select sections of ANSI/ASHRAE/IESNA 90.1-2019 Appendix G as described in Section 407.1.
3. Relative Performance Compliance: This pathway may be used by buildings not required to use Option 2. The Relative Performance Compliance pathway requires that the Proposed building complies with Sections C401.3, C402.1.5, C402.2.8, C402.3, C402.4, C402.5, C402.6, C402.7, C403.5, C403.7, C405.2.4, C405.13, C406, C407.2, C408, and ANSI/ASHRAE/IESNA 90.1-2019 using the Appendix G compliance pathway as modified in Section C407.2. Exception: Additions, alterations, repairs and changes of occupancy to existing buildings complying with Chapter 5. This exception does not include tenant space fit out zones when constructed for the first time. C401.2.2 Certified Performance Standard Compliance. Commercial buildings or portions thereof when following C401.2.4 shall comply with one of the following certified performance standards:
4. Passive House Compliance: This pathway can be used for any building of any size. This pathway requires compliance with Sections C401.3, C402.3, C405, C407.3 and C408.
5. HERS Compliance: This pathway can be used for any Group R occupancy building with multiple individual dwelling units. The HERS pathway requires compliance with Section C401.3, C402.3, C405, C407.4 and C408. For multi-family buildings with more than 8 units, air leaking testing using sampling in accordance with Section C402.5.2.2 and the RESNET MINHERS standard may be used. C401.2.4 Add Section C401.2.4 as follows: C401.2.4 Mixed use buildings. Where different building use types within a building require different Section C401.2 Compliance Pathways, each use type shall separately and individually show compliance with C401.2.1 or C401.2.2 for that respective use type. Exception: Enclosed or unenclosed parking garages that are part of a larger building may follow the Prescriptive Compliance path even where they exceed 20,000-sf. 2/14/25 225 CMR - 241

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C401.4 Add Section as follows: C401.4 Building electrification. Building projects which utilize Section C407.2.1 shall conform with C401.4.1. Building projects which utilize Section C402.1.5.2 shall conform with C401.4.2 except for buildings using the Relative Performance pathway because average ventilation at full occupancy is greater than 0.5 cfm/sf which shall comply with C401.4.1 rather than C401.4.2. Building projects which utilize Section CC104.1, Part 1 shall conform with C401.4.3. C401.4.1 Partial space heating electrification. Electric air source, exhaust source, or ground source heat pump systems shall supply 25% of the building's peak space heating and ventilation air heating load at the ASHRAE 99.6% winter climatic design condition. Heat pumps used for space and ventilation air heating shall comply with C401.4.4. C401.4.1.1 Heat pump primary operation. The heat pumps shall be controlled to prioritize their primary operation, prior to operation of supplemental fossil-fuel equipment, during non-emergency conditions. C401.4.2 Full space heating electrification. Electric air source, exhaust source, or ground source heat pump systems shall supply 100% of the building's peak space heating and ventilation air heating load at the ASHRAE 99.6% winter climatic design condition. No fossil fuel heating equipment shall be used for space heating or ventilation air heating. Heat pumps used for space and ventilation air heating shall comply with C401.4.4. C401.4.3 Full space and water heating electrification. Electric air source, exhaust source, or ground source heat pump systems shall supply 100% of the building's peak space heating and ventilation air heating load at the ASHRAE 99.6% winter climatic design condition. Electric air source, ground source, electric resistance, or solar thermal systems shall supply 100% of the building's service water. No fossil fuel equipment shall be used for space heating, ventilation air heating, or service water heating. Heat pumps used for space and ventilation air heating shall comply with C401.4.4. Heat pump service water heating shall conform to the applicable efficiencies in Section C404.2. Solar thermal service water shall have a solar fraction of 0.4 or larger. C401.4.4 Heat pump requirements. Heat pumps used for space heating and ventilation air heating shall comply with C401.4.4.1 through C401.4.4.3. C401.4.4.1 Equipment efficiencies. Heat pump equipment shall conform to the applicable efficiencies in Section C403.3.2. C401.4.4.2 Multiple systems. For buildings with multiple heat pump systems, compliance shall be based on the combined capacity of all heat pump systems serving the building. For purposes of this calculation, the heating capacity of a heat pump system shall not exceed the heating load of that system and the portion of the building served by that system. C401.4.4.3 Exhaust source heat pumps. For purposes of this calculation, the capacity of exhaust source heat pumps shall only include the heating capacity that exceeds the energy recovered by the minimum ventilation heat recovery required by C403.7.4. In addition, for purposes of this calculation, the capacity of the exhaust source heat pumps shall not exceed the heat pump capacity when the exhaust airflow is at 50% of design airflow. SECTION C402 BUILDING ENVELOPE REQUIREMENTS C402.1.3 Delete Section C402.1.3 and Table C402.1.3 and mark as Reserved. C402.1.3 Reserved. C402.1.4.1.1 Revise as follows: C402.1.4.1.1 Tapered, above-deck insulation based on thickness. Where used as a component of a maximum roof/ceiling assembly U-factor calculation, the sloped roof insulation R-value contribution to that calculation shall use the thickness at a point 1 inch thicker than the minimum along with the material R-value-per-inch (per-mm) solely for U-factor compliance as prescribed in Section C402.1.4. 2/14/25 225 CMR - 242

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C402.1.5 Revise Section C402.1.5 as follows: C402.1.5 Component performance alternative. Above grade wall values, fenestration values, and fenestration areas determined in accordance with C402.1.5.1 or C402.1.5.2 shall be an alternative to compliance with vertical above grade wall U- factors in Tables C402.1.4 and vertical fenestration U- factors in Table C402.4 and the maximum allowable fenestration areas in Section C402.4.1. Fenestration shall meet the applicable SHGC requirements of Section C402.4.3. Buildings following ANSI/ASHRAE/IESNA 90.1-2019 Appendix G shall comply with this section. Roofs, below grade walls, floors, slab-on-grade floors, and opaque doors shall comply with the values in Table C402.1.4. C402.1.5.1 Low glazed wall system buildings. Buildings in which less than or equal to 50% of the total, above-grade wall area of the building thermal envelope is a glazed wall system shall comply with Equation 4-2a and vision glass used in the glazed wall system shall have a maximum whole assembly U factor of U-0.25. Area-weighted U proposed <= 0.1285 (Equation 4-2a) where: Area-weighted U proposed = U value for each distinct assembly type of the above grade wall portion of the building thermal envelope weighted by vertical area for each distinct assembly type. Exception: Existing buildings following Section C505 (Change of Use) to create new R-use residential dwelling units with vision glass having a maximum whole assembly U factor of U-0.30 may comply by either: (1) each dwelling unit complies with Section C407.4 HERS Index for multi-family buildings, or (2) the building complies with Section C401.4.2 and the vertical envelope complies with Equation 4-2c. Area-weighted U proposed <= 0.1440 (Equation 4-2c) C402.1.5.2 High glazed wall system buildings. Buildings in which more than 50% of the total, above-grade wall area of the building thermal envelope is a glazed wall system shall comply with Equation 4-2b, and vision glass used in the glazed wall system shall have a maximum whole assembly U factor of U-0.25, the building shall comply with Section C401.4.2. Area-weighted U proposed <= 0.1600 (Equation 4-2b) where: Area-weighted U proposed = U value for each distinct assembly type of the above grade wall portion of the building thermal envelope, weighted by vertical area for each distinct assembly type. Exception: Buildings using the Relative Performance pathway because average ventilation at full occupancy is greater than 0.5 cfm/sf shall comply with C401.4.1 rather than C401.4.2. C402.2.1.2 Delete Section C402.2.1.2 C402.2.4.1 Delete the exception in Section C402.2.4.1: C402.2.8 Add Subsection C402.2.8 as follows: C402.2.8 Fireplaces. New combustion fireplaces shall have tight-fitting flue dampers or doors, and outdoor combustion air as required by the fireplace construction provisions of MA Construction Codes, as applicable. Where using tight-fitting doors on factory-built fireplaces listed and labeled in accordance with UL 127, the doors shall be tested and listed for the fireplace. 2/14/25 225 CMR - 243

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C402.3 Replace Section C402.3 with the following: C402.3 Rooftop solar readiness (mandatory). Follow Appendix CB: Solar-ready zone – Commercial. C402.4 Revise Section C402.4 as follows: C402.4 Fenestration. Fenestration shall comply with Sections C402.4.1 through C402.4.5 and Table C402.4. Daylight responsive controls shall comply with this section and Section C405.2.4. Exception: Revolving doors shall not be subject to the requirements of C402.1.4 and C402.4. Revolving doors may use representative U-factors contained in ASHRAE Handbook of Fundamentals, Chapter 15, Table 7 when showing compliance with C402.1.5. Table C402.4 Modify Vertical fenestration U-factors in TABLE C402.4 as follows: TABLE C402.4 BUILDING ENVELOPE FENESTRATION MAXIMUM U-FACTOR CLIMATE ZONE 5 AND MARINE 4 Vertical fenestration U-factor Fixed fenestration 0.30 Operable fenestration 0.32 C402.4.6 Add Subsection C402.4.6: C402.4.6 Fenestration documentation. In accordance with Section 303.1.3 fenestration performance shall be documented according to C402.4.6.1 or C402.4.6.2. C402.4.6.1 Labeled performance. The thermal transmittance of glazed fenestration products within the scope of NFRC shall be indicated by labels applied to the products at the manufacturing location or by a label certificate produced by an NFRC Approved Calculation Entity. C402.4.6.2 Calculated performance. Fenestration products outside the scope of NFRC may demonstrate compliance by submitting a thermal simulation report prepared by a registered design professional for each product as defined by NFRC 100. Thermal simulations shall be performed in accordance with the NFRC 100-2020 simulation procedures. It is acceptable to area-weight the modeled fenestration U-value based on the relative proportions of fixed and operable windows and window sizes. It is also acceptable to simplify the calculations by assuming the worst case by using the highest window U-value for all fenestration specified on the project. C402.5 Revise Section C402.5 as follows: C402.5 Air leakage - thermal envelope. The building thermal envelope shall comply with Sections C402.5.1 through Section C402.5.10.1. 402.5.1.1 Replace Section with the following: C402.5.1 Air barriers. A continuous air barrier shall be provided throughout the building thermal envelope. The continuous air barrier is permitted to be any combination of inside, outside, or within the building thermal envelope. The air barrier shall comply with Sections C402.5.1.1, and C402.5.1.2. The air leakage performance of the air barrier shall be verified in accordance with Section C402.5.2. 2/14/25 225 CMR - 244

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued 402.5.1.1 Replace Section C402.5.1.1 with the following: C402.5.1.1 Air barrier design and documentation requirements. Design of the continuous air barrier shall be documented in the following manner:

1. Materials, assemblies, and systems comprising the continuous air barrier and their position within each building thermal envelope assembly shall be identified.
2. Joints, interconnections, and penetrations of the continuous air barrier materials, assemblies, and systems shall be detailed.
3. The continuity of the air barrier at building element assemblies that enclose conditioned space or provide a boundary between conditioned space and unconditioned space shall be identified.
4. Documentation of the continuous air barrier shall detail methods of sealing the air barrier such as wrapping, caulking, gasketing, taping or other approved methods at the following locations: i. Joints around fenestration and door frames. ii. Joints between walls and floors, between walls at building corners, between walls and roofs including parapets and copings, where above-grade walls meet foundations and similar intersections. iii. Penetrations or attachments through the continuous air barrier in building envelope roofs, walls, and floors. iv. Building assemblies used as ducts or plenums. v. Changes in continuous air barrier materials and assemblies. vi. Transition from one wall or roof assembly type to another such as, but not limited to, transition between opaque wall system and glazed wall system, and transition between a curtain wall glazed wall system and a storefront glazed wall system.
5. Identify where testing will or will not be performed in accordance with Section C402.5.2. Where testing will not be performed, a plan for field inspections required by C402.5.2.3 shall be provided that includes the following: i. Schedule for periodic inspection(s), ii. Continuous air barrier scope of work, iii. List of critical inspection items, iv. Inspection documentation requirements, and v. Provisions for corrective actions where needed. C402.5.1.2 Replace Section C402.5.1.2 with the following: C402.5.1.2 Air barrier construction. The continuous air barrier shall be constructed to comply with the following:
6. The air barrier shall be continuous for all assemblies that comprise the building thermal envelope and across the joints and assemblies.
7. Air barrier joints and seams shall be sealed, including sealing transitions in places and changes in materials. The joints and seals shall be securely installed in or on the joint for its entire length so as not to dislodge, loosen or otherwise impair its ability to resist positive and negative pressure differentials such as those from design wind load, stack effect and mechanical ventilation.
8. Penetrations of the air barrier shall be caulked, gasketed or otherwise sealed in a manner compatible with the construction materials and location. Sealing shall allow for expansion, contraction and mechanical vibration. Sealing materials shall be securely installed around the penetration so as not to dislodge, loosen or otherwise impair the penetrations' ability to resist positive and negative pressure. Sealing of concealed fire sprinklers, where required, shall be in a manner that is recommended by the fire sprinkler manufacturer. Caulking or other adhesive sealants shall not be used to fill voids between fire sprinkler cover plates and walls or ceilings. 2/14/25 225 CMR - 245

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued 4. Recessed lighting fixtures shall comply with C402.5.9. Where similar objects are installed that penetrate the air barrier, provisions shall be made to maintain the integrity of the air barrier. 5. Electrical and communication boxes shall comply with C402.5.1.2.2 C402.5.1.2.1 Add Section C402.5.1.2.1 as follows: C402.5.1.2.1 Electrical and communication boxes. Electrical and communication boxes that penetrate the air barrier of the building thermal envelope, and that do not comply with C402.5.1.2.1.1, shall be caulked, taped, gasketed, or otherwise sealed to the air barrier element being penetrated. All openings on the concealed portion of the box shall be sealed. Where present, insulation shall rest against all concealed portions of the box. C402.5.1.2.1.1 Add Section C402.5.1.2.1.1 as follows: C402.5.1.2.1.1 Air-sealed boxes. Where air-sealed boxes are installed, they shall be marked in accordance with NEMA OS 4. Air-sealed boxes shall be installed in accordance with the manufacturer's instructions. C402.5.1.3 Delete Section C402.5.1.3 C402.5.1.4 Delete Section C402.5.1.4 C402.5.1.5 Delete Section C402.5.1.5 C402.5.2 Replace Section C402.5.2 as follows: C402.5.2 Air leakage compliance. Air leakage of the building thermal envelope shall be tested by an approved third party in accordance with C402.5.2.1. The measured air leakage shall not be greater than 0.35 cfm/ft 2 (1.8 L/s × m 2 ) of the building thermal envelope area at a pressure differential of 0.3 inch water gauge (75 Pa) with the calculated building thermal envelope surface area being the sum of the above- and below-grade building thermal envelope. Exceptions:

1. Where the measured air leakage rate is greater than 0.35 cfm/ft 2 (1.8 L/s × m 2 ) but is not greater than 0.45 cfm/ft 2 (2.3 L/s × m 2 ), the approved third party shall perform a diagnostic evaluation in accordance with ASTM E1186. All identified leaks shall be sealed where such sealing can be made without damaging existing building components. A report specifying the corrective actions taken to seal leaks shall be deemed to establish compliance with the requirements of this section where submitted to the code official and the building owner. Where the measured air leakage rate is greater than 0.45 cfm/ft2 (2.3 L/s × m 2 ), corrective actions must be made to the building and an additional test completed for which the results are 0.45 cfm/ft 2 (2.3 L/s × m 2 ), or less.
2. As an alternative, buildings or portions of buildings, containing Group R and I occupancies, shall be permitted to be tested by an approved third party in accordance with C402.5.2.2. The reported air leakage of the building thermal envelope shall not be greater than 0.27 cfm/ft 2 (1.4 L/s x m 2 ) of the testing unit enclosure area at a pressure differential of 0.2 inch water gauge (50 Pa). C402.5.2.1 Add Section C402.5.2.1 as follows: C402.5.2.1 Whole building test method and reporting. The building thermal envelope shall be tested for air leakage in accordance with ASTM E3158 or an equivalent approved method. A report that includes the tested surface area, floor area, air by volume, stories above grade, and leakage rates shall be submitted to the code official and the building owner. 2/14/25 225 CMR - 246

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Exceptions:

1. For buildings less than 10,000 ft 2 (1000 m 2 ), the entire building thermal envelope shall be permitted to be tested in accordance with ASTM E779, ASTM E3158 or ASTM E1827 or an equivalent approved method.
2. For buildings greater than 50,000 ft 2 (4645 m 2 ), portions of the building shall be permitted to be tested and the measured air leakage shall be area-weighted by the surface areas of the building thermal envelope in each portion. The weighted average tested air leakage shall not be greater than the whole building leakage limit. The following portions of the building shall be tested: i. The entire building thermal envelope area of stories that have any conditioned spaces directly under a roof. ii. The entire building thermal envelope area of stories that have a building entrance, a floor over unconditioned space, a loading dock, or that are below grade. iii. Representative above-grade portions of the building totaling not less than 25% of the wall area enclosing the remaining conditioned space. C402.5.2.2 Add Section C402.5.2.2 as follows: C402.5.2.2 Dwelling and sleeping unit enclosure test method and reporting. The building thermal envelope shall be tested for air leakage in accordance with ASTM E779, ANSI/RESNET/ICC 380, ASTM E1827, ASTM E3158, or an equivalent approved method. Where multiple dwelling units or sleeping units or other occupiable conditioned spaces are contained within one building thermal envelope, each unit shall be considered an individual testing unit, and the building air leakage shall be the weighted average of all testing unit results, weighted by each testing unit enclosure area. Units shall be tested without simultaneously pressurizing adjacent units and shall be separately tested as follows:
3. Where buildings have less than eight testing units, each testing unit shall be tested.
4. Where buildings have eight or more testing units, the greater of seven units or 20% of the testing units in the building shall be tested, including a top floor unit, a middle floor unit, a ground floor unit and a unit with the largest testing unit enclosure area. For each tested unit that exceeds the maximum air leakage rate, an additional three units shall be tested, including a mixture of testing unit types and locations.
5. Enclosed spaces with not less than one exterior wall in the building thermal envelope shall be tested in accordance with C402.5.3. Exception: Corridors, stairwells, and enclosed spaces having a conditioned floor area not greater than 1,500 ft 2 shall be permitted to comply with Section C402.5.1.5 and either Section C402.5.1.3 or C402.5.1.4. C402.5.2.3 Replace Section C402.5.2.3 with the following: C402.5.2.3 Building envelope design and construction verification criteria. In addition to the requirements of Sections C402.5.2.1 and C402.5.2.2, the installation of the continuous air barrier shall be verified by the code official, a registered design professional or approved agency in accordance with the following:
6. A review of the construction documents and other supporting data shall be conducted to assess compliance with the requirements in Section C402.5.1.
7. Inspection of continuous air barrier materials, assemblies, and systems shall be conducted during construction to verify compliance with the requirements of Sections C402.5.2.3.1 or C402.5.2.3.2. The air barrier shall remain accessible for inspection and repair.
8. A final inspection report shall be provided for inspections completed by the registered design professional or approved agency. The inspection report shall be provided to the building owner or owner's authorized agent and the code official. The report shall identify deficiencies found during inspection and details of corrective measures taken. 2/14/25 225 CMR - 247

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C402.5.2.3.1 Replace Section C402.5.2.3.1 with the following: C402.5.2.3.1 Materials. Materials with an air permeability not greater than 0.004 cfm/ft 2 (0.02 L/s × m 2 ) under a pressure differential of 0.3 inch water gauge (75 Pa) where tested in accordance with ASTM E2178 shall comply with this section. Materials in Items 1 through 16 below shall be deemed to comply with this section, provided that joints are sealed and materials are installed as air barriers in accordance with the manufacturer's instructions. i. Plywood with a thickness of not less than d inch (10 mm). ii. Oriented strand board having a thickness of not less than d inch (10 mm). iii. Extruded polystyrene insulation board having a thickness of not less than ½ inch (12.7 mm). iv. Foil-back polyisocyanurate insulation board having a thickness of not less than ½ inch (12.7 mm). v. Closed-cell spray foam having a minimum density of not less than 1.5 pcf (2.4 kg/m 3 ) and having a thickness of not less than 1½ inches (38 mm). vi. Open-cell spray foam with a density between greater than 0.4 and less than 1.5 pcf (0.6 and 2.4 kg/m 3 ) and having a thickness of not less than 4.5 inches (113 mm). vii. Exterior or interior gypsum board having a thickness of not less than ½ inch (12.7 mm). viii. Cement board having a thickness of not less than ½ inch (12.7 mm). ix. Built-up roofing membrane. x. Modified bituminous roof membrane. xi. Single-ply roof membrane. xii. A Portland cement/sand parge, or gypsum plaster having a thickness of not less than e inch (15.9 mm). xiii. Cast-in-place and precast concrete. xiv. Fully grouted concrete block masonry. xv. Sheet steel or aluminum. xvi. Solid or hollow masonry constructed of clay or shale masonry units. C402.5.2.3.2 Replace Section C402.5.2.3.2 with the following: C402.5.2.3.2 Assemblies. Assemblies of materials and components with an average air leakage not greater than 0.04 cfm/ft 2 (0.2 L/s × m 2 ) under a pressure differential of 0.3 inch of water gauge (75 Pa) where tested in accordance with ASTM E2357, ASTM E1677, ASTM D8052 or ASTM E283 shall comply with this section. Assemblies listed in Items 1 through 3 below shall be deemed to comply, provided that joints are sealed and the requirements of Section C402.5.1.1 are met.

1. Concrete masonry walls coated with either one application of block filler or two applications of a paint or sealer coating.
2. Masonry walls constructed of clay or shale masonry units with a nominal width greater than or equal to 4 inches (102 mm).
3. A Portland cement/sand parge, stucco or plaster not less than ½ inch (12.7 mm) in thickness. C402.5.3 Replace Section C402.5.3 with the following: C402.5.3 Air leakage of fenestration. The air leakage of fenestration assemblies shall comply with Table C402.5.3. Testing shall be conducted by an accredited, independent testing laboratory in accordance with the applicable reference test standard in Table C402.5.3 and labeled by the manufacturer. Exceptions:
4. Field-fabricated fenestration assemblies that are sealed in accordance with Section C402.5.1.2. 2/14/25 225 CMR - 248

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued 2. Fenestration in buildings that are tested for air leakage of in accordance with Section C402.5.2 are not required to meet the air leakage requirements in Table C402.5.3. TABLE C402.5.3 MAXIMUM AIR LEAKAGE RATE FOR FENESTRATION ASSEMBLIES Fennestration Assembly Maximum Rate (Cfm/ft 2 ) Test Procedure Windows 0.20 a AAMA/WDMA/CSA101/I.S.2/A440 or NRFC 400 Sliding doors 0.20 a Swinging doors 0.20 a Skylights – with condensation weepage openings 0.30 Skylights – all other 0.20 a Curtain walls 0.06 NRFC 400 or ASTM E283 at 1.57 psf (75 Pa) Storefront glazing 0.06 Commercial glazed swinging entrance doors 1.00 Power-operated sliding doors and power operated folding doors 1.00 Revolving doors 1.00 Garage doors 0.40 ANSI/DASMA 105, NRFC 400, or ASTM E283 at 1.57 psf (75 Pa) Rolling doors 1.00 High-speed doors 1.30 For SI: 1 cubic foot per minute = 0.47 L/s, 1 square foot = 0.093 m 2 a. The maximum rate for windows, sliding and swinging doors, and skylights is permitted to be 0.3 cfm per square foot of fenestration or door area when tested in accordance with AAMA/WDMA/CSA101/I.S.2/A440 at 6.24 psf (300 Pa). C402.5.4 Replace Section C402.5.4 with the following: C402.5.4 Rooms containing fuel-burning appliances. In Climate Zones 3 through 8, where combustion air is supplied through openings in an exterior wall to a room or space containing a space-conditioning fuel-burning appliance, one of the following shall apply:

1. The room or space containing the appliance shall be located outside of the building thermal envelope.
2. The room or space containing the appliance shall be enclosed and isolated from conditioned spaces inside the building thermal envelope. Such rooms shall comply with all of the following:
3. The walls, floors and ceilings that separate the enclosed room or space from conditioned spaces shall be insulated to be not less than equivalent to the insulation requirement of below-grade walls as specified in Table C402.1.4.
4. The walls, floors and ceilings that separate the enclosed room or space from conditioned spaces shall be sealed in accordance with Section C402.5.1.2.
5. The doors into the enclosed room or space shall be fully gasketed.
6. Piping serving as part of a heating or cooling system and ducts in the enclosed room or space shall be insulated in accordance with Section C403. Service water piping shall be insulated in accordance with Section C404.
7. Where an air duct supplying combustion air to the enclosed room or space passes through conditioned space, the duct shall be insulated to an R-value of not less than R-8. 2/14/25 225 CMR - 249

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00 continued Exception: Fireplaces and stoves complying with Sections 901 through 905 of the International Mechanical Code, and Section 2111.14 of the International Building Code. C402.5.5 Replace Section C402.5.5 with the following: C402.5.5 Doors and access openings to shafts, chutes, stairways and elevator lobbies. Doors and access openings from conditioned space to shafts, chutes stairways and elevator lobbies not within the scope of the fenestration assemblies covered by Section C402.5.3 shall be gasketed, weather-stripped or sealed. Exceptions:

1. Door openings required to comply with Section 716 of the International Building Code.
2. Doors and door openings required by the International Building Code to comply with UL 1784. C402.5.6 Replace Section C402.5.6 with the following: C402.5.6 Air intakes, exhaust openings, stairways and shafts. Stairway enclosures, elevator shaft vents and other outdoor air intakes and exhaust openings integral to the building envelope shall be provided with dampers in accordance with Section C403.7.7. C402.5.7 Replace Section C402.5.7 with the following: C402.5.7 Loading dock weather seals. Cargo door openings and loading door openings shall be equipped with weather seals that restrict air leakage and provide direct contact along the top and sides of vehicles that are parked in the doorway. C402.5.8 Replace Section C402.5.8 with the following: C402.5.8 Vestibules. Building entrances shall be protected with an enclosed vestibule. Doors opening into and out of the vestibule shall be equipped with self-closing devices. Vestibules shall be designed so that in passing through the vestibule it is not necessary for the interior and exterior doors to open at the same time. The installation of one or more revolving doors in the building entrance shall not eliminate the requirement that a vestibule be provided on any doors adjacent to revolving doors. Exceptions: Vestibules are not required for the following:
3. Doors not intended to be used by the public, such as doors to mechanical or electrical equipment rooms, or intended solely for employee use.
4. Doors opening directly from a sleeping unit or dwelling unit.
5. Doors that open directly from a space less than 3,000 sq. ft. (298 m 2 ) in area.
6. Revolving doors.
7. Doors used primarily to facilitate vehicular movement or material handling and adjacent personnel doors.
8. Doors that have an air curtain with a velocity of not less than 6.56 feet per second (2 m/s) at the floor that have been tested in accordance with ANSI/AMCA 220 and installed in accordance with the manufacturer's instructions. Manual or automatic controls shall be provided that will operate the air curtain with the opening and closing of the door. Air curtains and their controls shall comply with Section C408.2.3. C402.5.9 Replace Section C402.5.9 with the following: C402.5.9 Recessed lighting. Recessed luminaires installed in the building thermal envelope shall be all of the following:
9. IC-rated.
10. Labeled as having an air leakage rate of not greater than 2.0 cfm (0.944 L/s) where tested in accordance with ASTM E283 at a 1.57 psf (75 Pa) pressure differential.
11. Sealed with a gasket or caulk between the housing and interior wall or ceiling covering. 2/14/25 225 CMR - 250

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C402.5.10 Replace Section C402.5.10 with the following: C402.5.10 Operable openings interlocking. Where occupancies have operable openings to the outdoors that are larger than 40 sq. ft. (3.7 m 2 ) in area, such openings shall be interlocked with the heating and cooling system to raise the cooling setpoint to 90°F (32°C) and lower the heating setpoint to 50°F (10°C) whenever the operable opening is open. The change in heating and cooling setpoints shall occur when the operable opening has been open for a period not to exceed 10 minutes. Exceptions:

1. Operable openings into separately zoned areas associated with the preparation of food that contain appliances that contribute to the HVAC loads of a restaurant or similar type of occupancy.
2. Storage occupancies that utilize overhead doors for the function of the occupancy, where approved by the code official.
3. Doors located in the exterior wall that are part of a vestibule system.
4. Operable openings used as part of a designed system for natural ventilation. C402.5.10.1 Replace Section C402.5.10.1 with the following: C402.5.10.1 Operable controls. Controls shall comply with Section C403.13. C402.6 Add Section C402.6 as follows: C402.6 Approved calculation software tools. The following software tools are sufficient to demonstrate compliance with Sections C401.2.1 Prescriptive Compliance and C402.7 for projects up to 20,000 sq. ft.
5. COMcheck-Web available at: https://www.energycodes.gov/comcheck For projects over 20,000-sf, COMcheck may not be used for envelope compliance. Per Section C103.2(2), backstop compliance and thermal bridge derating calculations performed in accordance with latest edition of Massachusetts Stretch Energy Code Technical Guidance, Attachment A, Envelope Performance and Thermal Bridge Derating shall be provided. C402.7 Add Section C402.7 and subsections as follows: C402.7 Derating and Thermal Bridges C402.7.1 General. In addition to pre-calculated assembly U-factors, C-factors, or F-factors outlined in Appendix A of ASHRAE 90.1 2019, vertical envelope performance shall also take into account the effect of thermal bridges according to both C402.7.2 and C402.7.3. In addition, the thermal resistance of spandrel sections within glazed wall systems shall be according to C402.7.4. Together with Appendix A of ASHRAE 90.1 2019, these derated values and spandrel section values shall be used when showing compliance with Section C402.1.4 or Section C402.1.5, as applicable. C402.7.2 Continuous insulation for vertical walls. Installed vertical wall continuous insulation shall be derated using either C402.7.2.1, C402.7.2.2 or C402.7.2.3 to account for the effect of fasteners through the continuous insulation. 2/14/25 225 CMR - 251

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C402.7.2.1 Prescriptive derating. Derate vertical wall continuous insulation using Equation C402.7.2.1 and derating Factora from C402.7.2.1.1 for portions of wall having brick veneer systems and C402.7.2.1.2 or C402.7.2.1.3 for portions of wall having cladding systems. R derated = R o x Derating Factor (Equation C402.7.2.1) Where R derated : R value after derating, to be used when showing compliance R402.7.2 R o : R value of the continuous insulation prior to derating Derating Factor: From C402.7.2.1.1, C402.7.2.1.2, or C402.7.2.1.3 C402.7.2.1.1 Brick veneer systems. Wall systems comprised of brick anchor fasteners supporting brick veneer shall use a Derating Factor of 0.7 to account for the clear field thermal bridge derating effect of the fasteners. In addition, brick shelf angles shall be derated according to Section C402.7.3 to account for the linear thermal bridge derating effect of any brick shelf angles. C402.7.2.1.2 Cladding Systems. Wall systems comprised of cladding systems shall use derating factor per Table 402.7.2.1.2 Table 402.7.2.1.2 Cladding system derating factor Thickness of R o Derating Factor R o is less than or equal to R-15 Derating Factor = 0.74 – 0.021 x R o R o is greater than R-15 Derating Factor = 0.55 – 0.007 x R o C402.7.2.1.3 Cladding systems with qualifying thermal breaks. If plastic or fiberglass fasteners entirely comprised of material having thermal conductivity of 3 Btu-in/hr-ft2-F or less are used to support external cladding; or, if fasteners having thermal breaks which have a conductivity of 3 Btu-in/hr-ft 2 -F or less on both ends of the fastener are used to support external cladding, use Derating Factor of 0.8. C402.7.2.2. Reference derating. Use pre-solved, derated continuous insulation values contained in Building Envelope Thermal Bridging Guide, version 1.6 or higher, published by BC Hydro Power Smart at https://www.bchydro.com C402.7.2.3. Modelled derating. Use two or three-dimensional finite element analysis heat transfer model to calculate derated value. A three-dimensional model shall be used when there are point thermal bridges or thermal bridging in multiple planes. C402.7.3. Linear thermal bridges. In addition to derating per Section C402.7.2, installed vertical wall insulation U values shall be further derated for linear thermal bridges where the vertical wall intersects the following: brick shelf angles, balconies, vertical interior walls, horizontal interior walls, windows, roof, other vertical walls on different plane, and grade using Equation C402.7.3. 2/14/25 225 CMR - 252

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued (Equation C402.7.3) Where U derated Derated wall U value (Btu/hr-ft 2 -F) PSI Value from Section C402.7.3.1, C402.7.3.2, or C402.7.3.3 (Btu/hr-ft-F) Length Length of linear thermal bridge (ft) A total Area of derated wall (ft 2 ) U o Wall or roof U value prior to linear thermal bridge derating C402.7.3.1 Prescriptive PSI values. Use PSI values from Table C402.7.3.1 Table C402.7.3.1 Linear thermal bridge prescriptive PSI values. Type of Linear Thermal Bridge PSI-value (Btu/hr - ft – F) Balcony to exterior vertical wall intersection 1.00 Intermediate floor to exterior vertical wall intersection 0.60 Interior vertical wall to exterior vertical wall intersection 0.50 Fenestration to exterior vertical wall intersection 0.32 Parapet (vertical wall to roof intersection) 0.60 Brick shelf angle 0.35 Vertical wall to grade intersection 0.52 Vertical wall plane transition (building corners and other changes in vertical wall plane) 0.25 C402.7.3.2 Reference PSI values. Use pre-solved PSI values contained in Building Envelope Thermal Bridging Guide, version 1.6 or higher, published by BC Hydro Power Smart. C402.7.3.3 Modelled PSI values. Use a two or three-dimensional finite element analysis to calculate PSI values. A three-dimensional model shall be used when there are point thermal bridges or thermal bridging in multiple planes. C402.7.4 Thermal Resistance of Spandrel Sections. The R-factor of opaque spandrel sections within curtain wall systems shall be accordance with C402.7.4.1, C402.7.4.2, or C402.7.4.3. C402.7.4.1 Prescriptive R value. Opaque spandrel sections within glazed wall systems shall have at least R-12 insulation. For the purpose of calculating weighted U value in accordance with Section C402.1.5, spandrel sections shall use the default R values in Table C402.7.4.1. Table C402.7.4.1: Default R values for spandrel sections Type Default R-Value Thermally broken 3.5 Non-thermally broken 2 C402.7.4.2 Reference R values. Use pre-solved opaque spandrel sections R values contained in Building Envelope Thermal Bridging Guide, version 1.6 or higher, published by BC Hydro Power Smart. 2/14/25 225 CMR - 253

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C402.7.4.3. Modelled R values. Use a two or three-dimensional finite element analysis to calculate R value of opaque spandrel section. A three-dimensional model shall be used when there are point thermal bridges or thermal bridging in multiple planes. SECTION C403 BUILDING MECHANICAL SYSTEMS C403.3.2 Replace tables as follows: Replace 2021 IECC Table C403.3.2(8) with 2024 IECC Table CS403.3.2(8) Replace 2021 IECC Table C403.3.2(9) with 2024 IECC Table CS403.3.2(9) C403.5 Revise Section C403.5 as follows (Sections C403.5.1 through C403.5.5 remain unchanged): C403.5 Economizers. Economizers shall comply with Sections C403.5.1 through C403.5.5. An air or water economizer shall be provided for the following cooling systems:

1. Chilled water systems with a total cooling capacity, less cooling capacity provided with air economizers, as specified in Table C403.5(1).
2. Dedicated outside air systems
3. Individual fan systems with cooling capacity greater than or equal to 54,000 Btu/h (15.8 kW) in buildings having other than a Group R occupancy, the total supply capacity of all fan cooling units not provided with economizers shall not exceed 20 percent of the total supply capacity of all fan cooling units in the building or 300,000 Btu/h (88 kW), whichever is greater.
4. Individual fan systems with cooling capacity greater than or equal to 270,000 Btu/h (79.1 kW) in buildings having a Group R occupancy. The total supply capacity of all fan cooling units not provided with economizers shall not exceed 20 percent of the total supply capacity of all fan cooling units in the building or 1,500,000 Btu/h (440 kW), whichever is greater. Exceptions: Economizers are not required for the following systems.
5. Where more than 25 percent of the air designed to be supplied by the system is to spaces that are designed to be humidified above 35°F (1.7°C) dew-point temperature to satisfy process needs.
6. Systems expected to operate less than 20 hours per week.
7. Systems serving supermarket areas with open refrigerated casework.
8. Systems that include a heat recovery system in accordance with Section C403.10.5.
9. VRF systems installed with a dedicated outdoor air system. Table C403.5(1) Show only Climate Zone 5A. TABLE C403.5(1) MINIMUM CHILLED-WATER SYSTEM COOLING CAPACITY FOR DETERMINING ECONOMIZER COOLING REQUIREMENTS TOTAL CHILLED-WATER SYSTEM CAPACITY LESS CAPACITY OF COOLING UNITS WITH AIR ECONOMIZERS (Climate Zone 5A) Local water-cooled chilled-water systems Air-cooled chilled-water systems or district chilled-water systems 1,320,000 Btu/h 1,720,000 Btu/h For SI: 1 British thermal unit per hour = 0.2931 W. Table C403.5(2). Delete Table C403.5(2). C403.7.4 Replace Subsection C403.7.4 with the following: 2/14/25 225 CMR - 254

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C403.7.4 Energy recovery systems. Energy recovery ventilation systems shall be provided as specified in Section C403.7.4.1, as applicable and C403.7.4.2. C403.7.4.1 Revise Section C403.7.4.1 as follows: C403.7.4.1 Nontransient dwelling units. Nontransient dwelling units shall be provided with outdoor air energy recovery ventilation systems. Outdoor air must be delivered directly to the dwelling unit. The energy recovery system shall result in either 1 or 2, as applicable.

1. The system shall have an enthalpy recovery ratio of not less than 60% at cooling design condition and a sensible energy recovery ratio of not less than 75% at heating design condition. Outdoor air must be delivered directly to the dwelling unit. Compliance to the sensible energy recovery ratio and enthalpy recovery ratio shall be demonstrated by ratings generated at design conditions and airflows by software or catalogs certified by AHRI.
2. The system, at or above the design outdoor airflow, shall have a sensible recovery efficiency (SRE) that is not less than 72% at 32EF (0EC). The system shall have a total recovery efficiency (TRE) rating that is not less than 50% at 95°F (35°C). SRE and TRE shall be determined in accordance with CAN/CSA-C439 and compliance to the requirement shall be demonstrated by a listing in Home Ventilating Institute's Certified Product Directory. Linear interpolation of listed values for SRE shall be permitted. C403.7.4.2 Revise Section C403.7.4.2 as follows: C403.7.4.2 Spaces other than nontransient dwelling units. Where the supply airflow rate of a fan system serving a space other than a nontransient dwelling unit exceeds the values specified in Tables C403.7.4.2(1) and C403.7.4.2(2), the system shall include an energy recovery system. The energy recovery system shall result in either 1 or 2, as applicable. Where an air economizer is required, the energy recovery system shall include a bypass or controls that permit operation of the economizer as required by Section C403.5. Compliance to the sensible energy recovery ratio and enthalpy recovery ratio requirements shall be demonstrated by ratings generated at design conditions and airflows by software or catalogs certified by AHRI.
3. A sensible energy recovery ratio of at least 50% at heating design conditions for systems that provide makeup for Class 3 or 4 exhaust. Compliance to this limit shall be demonstrated by ratings at design conditions and airflows by software or catalog certified by AHRI. The requirement can be satisfied either for each fan system individually or based on a weighted average of the ventilation air flow for all applicable fan systems in the entire building per Equation C403.7.4.2(1). Equation C403.7.4.2(1) Weighted average sensible energy recovery ratio = [sensible energy recovery ratio for fan system 1 x outside air flow for system 1 + sensible energy recovery ratio for fan system 2 x outside air flow for system 2 + ... ]/[outside air flow for system 1 + outside air flow for system 2 + ...]
4. For all other systems a sensible energy recovery ratio of not less than 70% at heating design conditions and airflows, and enthalpy recovery ratio of not less than 60% at heating and cooling design conditions and airflows. The requirement can be satisfied either for each fan system individually or based on a weighted average of the ventilation air flow for all applicable fan systems in the entire building per Equation C403.7.4.2.(1) for sensible energy recovery ratio and Equation C403.7.4.2(2) for enthalpy recovery ratio. Equation C403.7.4.2(2) Weighted average enthalpy recovery ratio = [enthalpy recovery ratio for fan system 1 x outside air flow for system 1 + enthalpy recovery ratio for fan system 2 x outside air flow for system 2 + ... ]/[outside air flow for system 1 + outside air flow for system 2 + ...] 2/14/25 225 CMR - 255

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Where an air economizer is required, the energy recovery system shall include a bypass or controls that permit operation of the economizer as required by Section C403.5. Exception: An energy recovery ventilation system shall not be required in any of the following conditions:

1. Where energy recovery systems are prohibited by the International Mechanical Code.
2. Systems serving spaces that are heated to less than 40°F (10°C) and that are not cooled.
3. Systems expected to operate less than 10 hours per week at the outdoor air percentage covered by Table C403.7.4.2(1).
4. Systems exhausting toxic, flammable, paint or corrosive fumes or dust.
5. Commercial kitchen hoods used for collecting and removing grease vapors and smoke. Revise Tables C403.7.4.2(1) and C403.7.4.2(2) and show only Climate Zone 5A row, as follows: Table C403.7.4.2(1) ENERGY RECOVERY REQUIREMENT (Ventilation systems operating less than 8,000 hours per year) Climate Zone PERCENT (%) OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE

=10% and < 20% =20% and < 30% =30% and < 40% =40% and < 50% =50% and < 60% =60% and < 70% =70% and < 80% =80% Design Supply Fan Airflow Rate (cfm) 5A >= 10,000 >= 8,000 >= 2,750 >= 0 >= 0 >= 0 >= 0 >= 0 Table C403.7.4.2(2) ENERGY RECOVERY REQUIREMENT (Ventilation systems operating not less than 8,000 hours per year) Climate Zone PERCENT (%) OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE =10% and < 20% =20% and < 30% =30% and < 40% =40% and < 50% =50% and < 60% =60% and < 70% =70% and <80% =80% Design Supply Fan Airflow Rate (cfm) 5A >= 0 >= 0 >= 0 >= 0 >= 0 >= 0 >= 0 >= 0 C403.7.5 Revise Section C403.7.5 as follows: C403.7.5 Kitchen exhaust systems. Replacement air introduced directly into the exhaust hood cavity shall not be greater than 10% of the hood exhaust airflow rate. Conditioned supply air delivered to any space shall not exceed the greater of the following:

1. The ventilation rate required to meet the space heating or cooling load.
2. The hood exhaust flow minus the available transfer air from adjacent space where available transfer air is considered to be that portion of outdoor ventilation air not required to satisfy other exhaust needs, such as restrooms, and not required to maintain pressurization of adjacent spaces. Where total kitchen hood exhaust airflow rate is greater than 5,000 cfm (2360 L/s), each hood shall be a factory-built commercial exhaust hood listed by a nationally recognized testing laboratory in compliance with UL 710. Each hood shall have a maximum exhaust rate as specified in Table C403.7.5 and shall comply with one of the following:
3. Not less than 50% of all replacement air shall be transfer air that would otherwise be exhausted.
4. Demand ventilation systems on not less than 75% of the exhaust air that are configured to provide not less than a 50% reduction in exhaust and replacement air system airflow rates, including controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent and combustion products during cooking and idle.
5. Listed energy recovery devices with a sensible heat recovery effectiveness of not less than 40% on not less than 50% of the total exhaust airflow. Where a single hood, or hood section, is installed over appliances with different duty ratings, the maximum allowable flow rate for the hood or hood section shall be based on the requirements for the highest appliance duty rating under the hood or hood section. 2/14/25 225 CMR - 256

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Exception: Where not less than 75% of all the replacement air is transfer air that would otherwise be exhausted. TABLE C403.7.5 MAXIMUM NET EXHAUST FLOW RATE CFM PER LINEAR FOOT OF HOOD LENGTH Type of Hood Light-duty Equipment Medium-duty Equipment Heavy-duty Equipment Extra-heavy-duty Equipment Wall-mounted canopy 140 210 280 385 Single island 280 350 40 490 Double island (per side) 175 210 280 385 Eyebrow 175 175 NA NA Backshelf/ Pass-over 210 210 280 NA For SI: 1 cfm = 0.4719 L/s; 1 foot = 304.8 mm. NA = Not Allowed. SECTION C405 ELECTRICAL POWER AND LIGHTING SYSTEMS C405.2.4 Revise Section C405.2.4 as follows: C405.2.4 Daylight-responsive controls. Daylight responsive controls complying with Section C405.2.4.1 shall be provided to control the general lighting within daylight zones in the following spaces:

1. Spaces with a total of more than 100 watts of general lighting within primary sidelit daylight zones complying with Section C405.2.4.2.
2. Spaces with a total of more than 300 watts of general lighting within sidelit daylight zones complying with Section C405.2.4.2.
3. Spaces with a total of more than 100 watts of general lighting within toplit daylight zones complying with Section C405.2.4.3. C405.13 Add Section C405.13 as follows: C405.13 Electric vehicle ready parking spaces ("EV Ready Spaces") (Mandatory). New parking spaces shall provide EV Ready Spaces in accordance with Table C405.13. Installed wiring suitable for 6.6kW or higher SAE J3400 or SAE J1772-2017 AC Level II EVSE shall be connected to the service panel and run to within 6 feet (1828mm) of any qualifying parking space. Conductors and outlets for EVSE shall be sized and installed in accordance with the MA electrical code. TABLE C405.13 EV-READY SPACE REQUIREMENTS Occupancy Classification Minimum percentage of EV-Ready Spaces EV Charging Performance Requirements Group R and Group B 20% 40-amp dedicated branch circuit or larger branch circuit with ALMS in accordance with Table C405.13.1 All Other Occupancies 10% 40-amp dedicated branch circuit or larger branch circuit with ALMS in accordance with Table C405.13.1 2/14/25 225 CMR - 256.1

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Exceptions:

1. Parking spaces and garage spaces intended exclusively for storage of vehicles for retail sale or vehicle service are excluded from the EV-ready space percentage calculation.
2. Any parking facility with 4 or more spaces providing installed Direct Current fast charging EVSE with a minimum charging speed of 150 kW to each space.
3. One or more AC Level II spaces may be substituted with multiple AC Level I spaces provided with wiring for a minimum 20amp, 120-volt EVSE, with a ratio of at least 3 AC Level I spaces for each AC Level II space required.
4. Parking spaces specifically designated for medium or heavy-duty vehicles are excluded from the EV-ready space percentage calculation. C405.13.1 Modify Table C405.13.1 as follows: C405.13.1 Minimum Charging Performance Requirements. Automatic Load Management System (ALMS) may be used to control electric vehicle loads for EV-Ready or EVSE-Installed Spaces with AC Level II or Level I charging, subject to the performance requirements in Table C405.13.1. TABLE C405.13.1 EV-READY PERFORMANCE REQUIREMENTS Circuit Breaker Amperage Maximum Parking Spaces that May Share a Branch Circuit with 10% or more EV Ready spaces 40A 2 50A 2 60A 4 70A 6 80A 8 90A 9 100A 10 C405.13.2 Identification. Construction documents shall indicate the branch circuit termination point and proposed location of future EVSE. Construction documents shall also provide information on amperage of future EVSE, wiring schematics, Automatic Load Management Systems, and electrical load calculations to verify that the electrical panel service capacity and electrical system, including any on-site distribution transformers, have sufficient capacity to simultaneously charge all EVs at all required EV ready spaces. SECTION C406 ADDITIONAL EFFICIENCY REQUIREMENTS C406.1 Revise Section C406.1 as follows: C406.1 Additional energy efficiency credit requirements. New buildings shall achieve a total of 15 credits from Tables C406.1(1) through C406.1(5) where the table is selected based on the use group of the building and from credit calculations as specified in relevant subsections of Section C406. Where a building contains multiple-use groups, credits from each use group shall be weighted by floor area of each group to determine the weighted average building credit. Credits from the tables or calculation shall be achieved where a building complies with one or more of the following:
5. More efficient HVAC performance in accordance with Section C406.2.
6. Reduced lighting power in accordance with Section C406.3.
7. Enhanced lighting controls in accordance with Section C406.4.
8. On-site supply of renewable energy in accordance with Section C406.5.
9. Provision of a dedicated outdoor air system for certain HVAC equipment in accordance with Section C406.6.
10. High-efficiency service water heating in accordance with Section C406.7.
11. Enhanced envelope performance in accordance with Section C406.8.
12. Reduced air infiltration in accordance with Section C406.9
13. Where not required by Section C405.12, include an energy monitoring system in accordance with Section C406.10. 2/14/25 225 CMR - 256.2

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued 10. Where not required by Section C403.2.3, include a fault detection and diagnostics (FDD) system in accordance with Section C406.11. 11. Efficient kitchen equipment in accordance with Section C406.12. 12. Heavy Timber Construction in accordance with Section C406.13 13. Low GWP concrete mix in accordance with Section C406.14 14. Net zero GWP insulation in accordance with Section C406.15 C406.1.1 Add Subsection C406.1.1 as follows: C406.1.1 Tenant Spaces. Tenant spaces shall comply with sufficient options from Tables C406.1(1) through C406.1(5) to achieve a minimum number of 10 credits, where credits are selected from Section C406.2, C406.3, C406.4, C406.6, C406.7 or C406.10. Where the entire building complies using credits from C406.5, C406.8, or C406.9, tenant spaces shall be deemed to comply with this section. Exception: Previously occupied tenant spaces that comply with this code in accordance with Section C501. Table C406.1(1) through Table C406.1(5) In Table C406.1(1) through Table C406.1(5), delete rows for C406.2.1; Table C406.1(1) through Table C406.1(5) In Table C406.1(1) through Table C406.1(5), replace row for option C406.2.3 with the following: Section Climate Zone 5A C406.2.3 Renewable space heating 15 Table C406.1(1) through Table C406.1(5) In Table C406.1(1) through Table C406.1(5), delete rows for C406.7.3; Tables C406.1(1) through Table C406.1(5) add the following row for options C406.13, C406.14 and C406.15: Section Climate Zone 5A C406.13 Heavy Timber Construction 8 C406.14 Low GWP concrete mix 8 C406.15 Net zero GWP insulation 8 C406.2.1 Delete and Reserve Section C406.2.1 C406.2.1 Reserved. C406.2.3 Replace Section C406.2.3 as follows: C406.2.3. Renewable space heating. All space heating shall be provided with cold-climate air source heat pumps having rated coefficient of performance (COP) of at least 1.75 at 5 degrees Fahrenheit source air, or ground source heat pumps. Electric resistance shall not be used except for defrost function. C406.7.3 Delete and Reserve Section C406.7.3. C406.7.3 Reserved. 2/14/25 225 CMR - 256.3

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C406.9 Replace Section C406.9 with the following: C406.9 Reduced air leakage. Air leakage of the building thermal envelope shall be tested by an approved third party in accordance with Section C402.5.2.1. The measured air leakage shall not exceed 0.20 cfm/ft 2 (1.1 L/s × m 2 ) of the building thermal envelope at a pressure differential of 0.3 inch water gauge (75 Pa), with the calculated surface area being the sum of the above- and below-grade building thermal envelope. C406.13 Add Section C406.13 as follows: C406.13 Heavy Timber construction. For buildings with 4 stories or more of Type IV heavy timber construction either above grade, or above a podium. C406.14 Add Section C406.14 and Table C406.14 as follows: C406.14 Low GWP concrete mix. In new buildings where EPDs are provided with construction documentation 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 C406.14. C406.14.1 Documentation for low GWP concrete mix credit. In order to apply the low GWP concrete mix credits, the architect or engineer of record must submit specific EPDs for concrete used in the project. 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 C406.14 credits 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 C406.14. for at least 90% of all concrete used for the project. TABLE C406.14 DEFAULT CONCRETE GLOBAL WARMING POTENTIAL VALUES Maximum GWP (kg CO 2 e) Limits for Concrete NORMAL WEIGHT CONCRETE Specified Compressive Strength (f'c in psi) Maximum GWP per cubic meter a 0-2500 240 2501-3000 264 3001-4000 314 4001-5000 378 5001-6000 399 6001-8000 472 LIGHT WEIGHT CONCRETE Specified Compressive Strength (f'c in psi) Maximum GWP per cubic meter a 0-3000 517 3001-4000 573 4001-5000 628 a These 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 2/14/25 225 CMR - 256.4

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C406.15 Add Section C406.15 as follows: C406.15 Net zero GWP insulation. In new buildings that demonstrate an average calculated insulation Global Warming Potential (GWP) intensity (kg CO2e/m 2 ) less than 0 across the whole building envelope. GWP intensity shall be based on the default values in Table C406.15. or product specific EPDs or calculations in the approved tools: EC3 and BEAM, may be used in place of default table C406.15 values. C406.15.1 Documentation for insulation embodied carbon credit. In order to apply the insulation embodied carbon credits for a building, the architect or engineer of record for the building must submit a complete calculation to summarize estimated embodied carbon emissions from all insulation materials used in the building project. The output metric for this measure shall be Global Warming 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 (m 2 )
4. Default, industry-average GWP value, from Table C406.15 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 C406.15 Add Table C406.15 as follows: TABLE C406.15 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 CO 2 e/ sq.m. RSI-1 Cellular glass - Aggregate 3.93 b 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 1.93 c 2/14/25 225 CMR - 256.5

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Insulation Material Default Global Warming Potential (GWP) in Kg CO 2 e/ sq.m. RSI-1 Hemp - Batt -0.50 HempCrete -4.10 Mineral wool - Batt, unfaced 1.50 Mineral wool - Blown loose fill 1.90 Mineral wool - Board, unfaced, "light" density 2.70 f Mineral wool - Board, unfaced, "heavy" density 6.90 f Phenolic foam - Board 1.54 d Polysio - Wall Board 4.10 e Polyiso - Roof Board (GRF facer) 2.11 e Polyiso - Roof Board (CGF facer) 2.95 e 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 7.40 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 55.5 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 SECTION C407 TOTAL BUILDING PERFORMANCE CERTIFICATION METHODS C407 Replace Section C407 in its entirety as follows: C407.1 Targeted Performance This option requires compliance with Sections C407.1.1 through C407.1.2. 2/14/25 225 CMR - 256.6

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C407.1.1 Compliance. Buildings shall comply with Sections C407.1.1.1 through C407.1.1.6. C407.1.1.1 Building performance modeling. Building performance modeling shall be used to show compliance with C407.1.1.5. The simulation program shall be a computer-based program for the analysis of energy consumption in buildings. The simulation shall include calculation methodologies for the building components being modeled and meet the requirements in ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Section G2.2.1(a)-(d) and G2.2.4. C407.1.1.2 Climatic conditions. The simulation program shall perform the simulation using hourly values of climatic data using representative weather files prescribed by the Massachusetts Department of Energy Resources. C407.1.1.3 Modeling building envelope infiltration. The air leakage rate of the building envelope shall be modeled following ANSI/ASHRAE/IESNA 90.1-2019 Section G3.1.1.4. C407.1.1.4 Internal loads, scheduling, and other modeling assumptions Performance modeling shall use the internal load, scheduling, and other assumptions as prescribed by the Massachusetts Department of Energy Resources. C407.1.1.5 Thermal energy demand intensity (TEDI) limits Performance modeling shall show that the building's heating thermal energy demand intensity and cooling thermal energy demand intensity are less than or equal to the values in Table C407.1.1.5 Table C407.1.1.5 Thermal Energy Demand Intensity (TEDI) Limits Use Type Heating TEDI (kBtu/sf-yr) Cooling TEDI (kBtu/sf-yr) Office, fire station, library, police station, post office, town hall >= 125,000-sf 1.5 23 Office, fire station, library, police station, post office, town hall between 75,000 and 125,000-sf 4 - 0.00002 * Area (sf) 18 + 0.00004 * Area (sf) Office, fire station, library, police station, post office, town hall <= 75,000-sf 2.5 21 K-12 School >= 125,000-sf 2.2 12 K-12 School between 75,000 and 125,000-sf 2.7 - 0.000004 * Area (sf) 32 - 0.00016 * Area (sf) K-12 School <= 75,000-sf 2.4 20 Residential multifamily and dormitory >= 125,000-sf 2.8 22 Residential multifamily and dormitory between 75,000 and 125,000-sf 3.8 - 0.000008 * Area (sf) 4.5 + 0.00014 * Area (sf) Residential multifamily and dormitory <= 75,000-sf 3.2 15 All other >= 125,000-sf 1.5 23 All other between 75,000 and 125,0000-sf 4 - 0.00002 * Area (sf) 18 + 0.00004 * Area (sf) All other <= 75,000-sf 2.5 21 C407.1.1.6 Mixed use buildings. For buildings having more than one use type where any use type is more than 10% of the total space conditioned area, each separate use type having more than 10% of the total space conditioned area shall separately and individually show compliance with C407.1.1.5 for that respective use type. Use types having less than or equal to 10% of the total space conditioned area do not have to show separate, individual compliance with C407.1.1.5 but can be incorporated into and treated as the majority use type. 2/14/25 225 CMR - 256.7

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C407.1.2 Documentation. Simulated performance shall be documented, and documentation shall be submitted to the rating authority. Documentation shall include all the assumptions used in the performance modeling such that the documentation can be used as a specification checklist for implementation during design and construction. The information shall be submitted in a report and shall include the items described in ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Section G1.3.2 Parts b, g, h, i, j, k, l, n, o, and q, and Section G1.3.3. C407.2 Relative Performance. This option requires compliance with Section C407.2.1 and C407.2.2. C407.2.1 Add exception to C407.2.1 as follows: C407.2.1 Electrification and documentation of highly ventilated buildings. Buildings using the Relative Performance Pathway (C407.2) because average ventilation at full occupancy is greater than 0.5 cfm/sf shall have space heating electrified in accordance with Section C401.4.1 and shall submit design documents showing ventilation system design and air flow rates as required by Section C103.2 part 16. Exception: Space heating uses provided by a district energy system which is transitioning to a heat recovery enabled district energy system and subject to a district energy system order of conditions in good standing from the Commonwealth of Massachusetts Department of Energy Resources. C407.2.2 Compliance. Building shall comply with ANSI/ASHRAE/IESNA 90.1-2019 Section 4.2 using the Appendix G pathway as modified by C407.2.2.1 and C407.2.2.2. C407.2.2.1 Modification to ANSI/ASHRAE/IESNA 90.1-2019 Section 4.2. ANSI/ASHRAE/IESNA 90.1-2019 Section 4.2 Replace Section 4.2.1.1 with following: New buildings shall comply with 4.2.2 through 4.2.5 and normative Appendix G. When using Normative Appendix G, the Performance Energy Index (PEI) of new buildings, additions to existing buildings, and alterations to existing buildings shall be less than or equal to the Performance Energy Index Target (PEI t ) when calculated in accordance with the following: PEI t = [BBUE + (BPF x BBRE)]/BBSE (Equation C407.2.2.1) Where: PEI = Performance Energy Index calculated in accordance with Section G1.2 BBUE = Baseline building unregulated site energy BBRE = Baseline building regulated site energy BPF = Building performance factor from Table 4.2.1.1 For building area types not listed in Table 4.2.1.1 use “All others”. Where a building has multiple area types, the required BPF shall be equal to the area-weighted average of the building area types. BBSE = Baseline building site energy (sum of BBUE and BBRE) ANSI/ASHRAE/IESNA 90.1-2019 Section 4.2 Revise Table 4.2.1.1 to show only Climate Zone 5A; remove multifamily, office, and school; and adjust the BPFs as follows: 2/14/25 225 CMR - 256.8

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued TABLE 4.2.1.1 BUILDING PERFORMANCE FACTOR (BPF) Building Area Type Climate Zone 5A Health care/hospital 0.59 Hotel/motel 0.57 Restaurant 0.62 Retail 0.47 Warehouse 0.41 All others 0.51 C407.2.2.2 Modification to ANSI/ASHRAE/IESNA 90.1-2019 Appendix G ANSI/ASHRAE/IESNA 90.1-2019 Appendix G In all Sections of Appendix G, replace references to “baseline building performance” with “baseline building site energy”, replace “proposed building performance” with “proposed building site energy”, replace “energy cost savings” with “site energy savings” ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Replace G1.2.2 with following, keeping the exception unchanged: The site energy of the proposed design is calculated in accordance with the provisions of this appendix using the following formula: Performance energy index (PEI) = Proposed building site energy/baseline building site energy (BBSE) Both the proposed building site energy and the baseline building site energy shall include all end use load components within and associated with the building when calculating the performance energy index. ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Delete G1.3.2 Part m and Part p ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Delete G2.1 Part c ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Revise G2.4.1 as follows Site recovered energy shall be subtracted from the proposed building site energy when calculating performance. Energy used to recharge vehicles that are used for on-road and off-site transportation purposes, or energy losses from use of behind-the-meter energy storage, should not be included when calculating performance. On-site renewable energy shall not be subtracted from the proposed building site energy when calculating performance. ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Delete G2.4.2 ANSI/ASHRAE/IESNA 90.1-2019 Appendix G Add the following row to Section G Table G3.1.1-1. TABLE G3.1.1-1 BASELINE BUILDING VERTICAL FENESTRATION PERCENTAGE OF GROSS ABOVE-GRADE-WALL AREA Building Area Types Baseline Building Gross Above-Grade-Wall Area Multifamily 24% 2/14/25 225 CMR - 256.9

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C407.3 Add Section C407.3 as follows: C407.3 Passive House. This option requires compliance with Section C407.3.1 and C407.3.2. C407.3.1 Compliance. Projects may document compliance with either Phius certification in accordance with 407.3.2.1 or PHI certification in accordance with C407.3.2.1 or follow C407.3.2.3. Buildings shall be pre-certified as meeting the Phius CORE 2021 or Phius ZERO 2021 Passive Building Standard – North America, or newer, demonstrated using approved Passive House certification software and program criteria by PHIUS, where design-certification is demonstrated by Phius and a Certified Passive House Consultant or, Projects meeting the Certified Passive House standard using the approved Passive House certification software and program criteria by the Passive House Institute (PHI), where PHI certification is demonstrated by a PHI-accredited Certifier. C407.3.2 Documentation. Compliance with Phius or PHI shall be in accordance with C407.3.2.1 or C407.3.2.2 C407.3.2.1 Phius Documentation.

1. Prior to the issuance of a building permit, the following items must be provided to the Building Official: a. A Passive House Verification report with results from the approved Passive House certification software which demonstrates project compliance with Phius CORE 2021 (or newer), or Phius ZERO 2021 (or newer) performance requirements. b. A statement from the CPHC that the verification report results accurately reflect the plans submitted. c. Evidence of project registration from Phius. OR a. A Design Certification Letter from Phius.
2. Prior to the issuance of a final certificate of occupancy, the following item(s) must be provided to the building official:
   1. Design Certification Letter from Phius.
   2. An updated Passive House Verification Report with results from the approved
   Passive House certification software which reflects "as-built" conditions and test results (blower door and ventilation results) that demonstrate project compliance with Phius performance requirements. c. A statement from the CPHC that the envelope meets the Phius hygrothermal requirements found in Appendix B of the Phius 2021 Certification guidebook d. A statement from the Phius project Verifier that the project test results meet the model performance requirements, all the mandatory limits and any other mandatory requirements. e. A copy of the Phius workbook listing all testing results and as-built conditions. OR a. A Final Certification Letter, provided by Phius. AND f. Verfication of compliance with C405.13: EV ready, and Appendix CB: Solar Ready Provisions. C407.3.2.2 Passive House Institute (PHI) Documentation.
3. Prior to the issuance of a building permit, the following item(s) must be provided to the Building Official: a. A PHPP (Passive House Planning Package) compliance report with results from the approved Passive House certification software which demonstrates project compliance with current PHI performance requirements; b. A statement from the PHI-accredited Certifier that the approved Passive House certification software results and compliance report accurately reflect the plans submitted; c. Evidence of project registration from a PHI-accredited Certifier. OR 2/14/25 225 CMR - 256.10

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued a. A Design State Conditional Assurance Letter from a PHI-accredited Certifier. 2. Prior to the issuance of a final certificate of occupancy, the following items must be provided to the building official: a. A Design State Conditional Assurance Letter from a PHI-accredited Certifier. b. An updated compliance report with results from the approved Passive House certification software which reflects "as-built" conditions and test results (blower door and ventilation results) that demonstrates project compliance with PHI performance requirements; c. A copy of both the air leakage test results and report on the commission settings and performance of the building's ventilation system; d. A statement from the Certified Passive House Consultant or Certified Passive House Designer that the project test results meet the model performance requirements, all the mandatory limits and any other mandatory requirements. OR a. A Final Certification Letter from a PHI-accredited Certifier. AND e. Verification of compliance with C405.13: EV ready, and Appendix CB: Solar Ready Provisions. C407.3.2.3 Documentation for design certified Passive House projects that fail final certification. C407.3.2.3.1 Compliance. Buildings shall be pre-certified per Section C407.3.1. If, at construction completion, final certification cannot be received from either Phius or PHI, this compliance pathway may be followed to receive a certificate of occupancy based on compliance with C407.3.2.3.2 Documentation. Compliance via C407.3.2.3.2 is not equivalent to either Phius or PHI Certification and will not designate the project as a certified passive house. C407.3.2.3.2 Near Passive House Documentation. The following materials are required: a. Statement from the Phius certified consultant or PHI-accredited verifier confirming project has completed all interim, final, and corrective testing and modeling requirements, including a summary of deviations from certification requirements. b. Copy of executed contracts with Phius consultant or PHI rater/verifier covering all required inspections and testing requirements for certification. c. Design phase pre-certification/approval, in the form of a statement issued from Phius or PHI-accredited verifier confirming design certification or pre-certification was achieved. d. Report from rater/verifier demonstrating as-built conditions, including those that comply with Phius or PHI requirements, and those that do not. i. If the initial whole building blower door tests do not meet the Phius or PHI airtightness requirement, a statement must be provided to reflect evidence of a re-test. Statement shall include an explanation for sources of leakage and attempted remediation efforts. Final test results shall not exceed Phius or PHI airtightness thresholds by more than 30%. ii. If the mechanical ventilation flow rates and balance do not meet the requirements of Phius or PHI, report must show that installed ventilation system demonstrates compliance with the mechanical code in accordance with Section C403. e. For projects with Phius design certification, provide final Energy Star and Zero Energy Ready Homes certificates. f. A letter from a licensed professional engineer that states that the potential hygrothermal or moisture risk of the as-built assemblies, with the measured blower door test result, is acceptably low. C407.4 Add Section C407.4 as follows: C407.4 HERS Index for multi-family buildings. This option requires compliance with Section C407.4.1, C407.4.2, C407.4.3 2/14/25 225 CMR - 256.11

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued C407.4.1 Compliance. Each dwelling unit shall have a certified HERS Index (HERS) rating less than or equal to the appropriate value indicated in Table C407.4 when compared to the HERS index reference design for each dwelling unit prior to credit for onsite renewable electric generation. Buildings shall meet or exceed ENERGY STAR Multifamily New Construction (MFNC) program requirements. The Home Energy Rating Index (HERS) shall be determined in accordance with ANSI/RESNET/ICC Standard 301. Software tools used for determining HERS Index shall be Approved Software Rating Tools in accordance with ANSI/RESNET/ICC 301. Where calculations require input values not specified in Section C407.4, those input values shall be taken from ANSI/RESNET/ ICC 301. TABLE C407.4 MAXIMUM ENERGY RATING INDEX Clean Energy Application Maximum HERS Index score a New construction permits after July 1, 2024 New construction with R406.5.2 embodied carbon credit Major alterations, additions, or Change of use b Mixed-Fuel Building 42 45 55 Solar Electric Generation 42 45 58 All-Electric Building 45 48 58 Solar Electric & All-Electric Building 45 48 61 a Maximum HERS rating prior to onsite renewable electric generation in accordance with Section C407.4 b Alterations, Additions or Change of use covered by Sections C502, C503 or C505 are subject to this maximum HERS rating, except for Historic buildings which may opt to follow the prescriptive compliance pathway in C401 as applicable. C407.4.2 Documentation. Documentation verifying that the methods and accuracy of compliance software tools conform to the provisions of this section shall be provided to the building official in accordance with C407.4.3.1 and C407.4.3.2: C407.4.2.1 Prior to issuance of building permit. Prior to the issuance if a building permit, the following items must be provided to the Building Official:

1. Building street address, or other building site identification.
2. Declare the HERS Index on title page and building plans.
3. The name of the individual performing the analysis and generating the compliance report.
4. The name and version of the compliance software tool.
5. Documentation of all inputs entered into the software used to produce the results for the reference design and/or the rated home.
6. A certificate indicating that the proposed design has a HERS Index less than or equal to the appropriate score indicated in Table C407.4 when compared to the ERI reference design. The certificate shall document the building component energy specifications that are included in the calculation, including: component level insulation R-values or U-factors; assumed duct system and building envelope air leakage testing results; and the type and rated efficiencies of proposed heating, cooling, mechanical ventilation, and service water-heating equipment to be installed. If on-site renewable energy systems will be installed, the certificate shall report the type and production size of the proposed system.
7. When a site-specific report is not generated, the proposed design shall be based on the worst-case orientation and configuration of the rated home. C407.4.2.2 Prior to issuance of certificate of occupancy. Prior to the issuance of a certificate of occupancy, the following items must be provided to the Building Official:
8. Building street address or other building site identification.
9. Declaration of the Final HERS Index on title page and on building plans. 2/14/25 225 CMR - 256.12

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued 3. The name of the individual performing the analysis and generating the report. 4. The name and version of the compliance software tool. 5. Documentation of all inputs entered into the software used to produce the results for the reference design and/or the rated home. 6. A final confirmed certificate indicating that the confirmed rated design of the built home complies with Sections C407.4. The certificate shall report the energy features that were confirmed to be in the home, including: component-level insulation R-values or U-factors; results from any required duct system and building envelope air leakage testing; and the type and rated efficiencies of the heating, cooling, mechanical ventilation, and service water-heating equipment installed. 7. Documentation that each unit meets or exceeds ENERGY STAR Multifamily New Construction (MFNC) program requirements. 8. Where on-site renewable energy systems have been installed on or in the home, the certificate shall report the type and production size of the installed system. 9. Compliance with C405.13, and either Appendix CB or Appendix CC as applicable. 10. Optional compliance with R406.5.2 Embodied carbon credit as documented in accordance with R406.5.3 or R406.5.4 as applicable. C407.4.3 Verification by approved agency. Verification of compliance shall be completed by a certified HERS rater. Chapter 5: [CE] EXISTING BUILDINGS SECTION C501 GENERAL C501.2 Revise Section C501.2 and replace the exception to Section C501.2 as follows: C501.2 Compliance. Additions, alterations, repairs, and changes of occupancy to, or relocation of, existing buildings and structures shall comply with Sections C502, C503, C504 and C505 of this code, as applicable, and with the provisions for alterations, repairs, additions and changes of occupancy or relocation, respectively, in the International Building Code, International Existing Building Code, Massachusetts Fire Code, International Mechanical Code, Massachusetts Plumbing Code, and NFPA 70. Changes where unconditioned space is changed to conditioned space shall comply with Section C502. Exception: Additions, alterations, repairs or changes of occupancy complying with Section C506 EnerPHit standard compliance pathway or Section C401.2.2. SECTION C502 ADDITIONS C502.1 Revise Section C502.1 as follows: C502.1 General. Additions to an existing building where the addition is up to 100% of the size of the existing building and less than 20,000 sq. ft. shall comply with Sections C401.3, C402 through C406, and Section C408. Additions which exceed either of these limits shall comply with the applicable pathway for new construction in C401.2. Additions shall not create an unsafe or hazardous condition or overload existing building systems. An addition shall be deemed to comply with this code if the addition alone complies or if the existing building and addition comply with this code as a single building. C502.2 Remove both exceptions to Section C502.2 C502.3.7 Add Section C502.3.7 as follows: C502.3.7 Air Infiltration Testing. Additions shall be required to comply with air infiltration testing requirements in accordance with Section C402.5 for the addition only. 2/14/25 225 CMR - 256.13

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued SECTION C503 ALTERATIONS C503.1 Revise Section C503.1 as follows: C503.1 General. Alterations to any building or structure shall comply with the requirements of Section C503, and Sections C402, C403, C404, C405 of the code for new construction. Alterations shall be such that the existing building or structure is not less conforming to the provisions of this code than the existing building or structure was prior to the alteration. Alterations to an existing building, building system or portion thereof shall conform to the provisions of this code as those provisions relate to new construction without requiring the unaltered portions of the existing building or building system to comply with this code. Alterations shall not create an unsafe or hazardous condition or overload existing building systems. Exceptions: The following alterations need not comply with the requirements for new construction, provided that the energy use of the building is not increased:

1. Storm windows installed over existing fenestration.
2. Surface-applied window film installed on existing single-pane fenestration assemblies reducing solar heat gain, provided that the code does not require the glazing or fenestration to be replaced.
3. Where the component performance alternative in Section 402.1.5 is used to comply with this section, the proposed UA shall not be greater than 110% of the target UA.
4. Construction where the existing roof, wall or floor cavity is not exposed.
5. Roof recover.
6. Air barriers shall not be required for roof recover and roof replacement where the alterations or renovations to the building do not include alterations, renovations or repairs to the remainder of the building envelope.
7. Wall cavities that are exposed during construction shall comply with Section C402.1.4. Localized removal of interior finishes up to 10 ft 2 does not require upgrading the wall assembly to show compliance with Section C402.1.4. Localized exposed cavities shall be filled with insulation not less than R-4 / inch. C503.2 Revise Section C503.2 as follows: C503.2 Building envelope. New building envelope assemblies that are part of the alteration shall comply with Section C402. C503.2.4 Add Section C503.2.4 as follows: C503.2.4 Derating and Thermal Bridges. Existing linear thermal bridges inherent to the building structure and/or components that are not part of the alteration shall not be accounted for per C402.7.3. Construction documents shall include the following documentation in tabular format for these linear thermal bridges that may be excluded from vertical envelope performance:
8. Linear thermal bridge type.
9. Aggregate length of each type of linear thermal bridge.
10. Relevant detail in the construction documents showing a cross-section through the thermal bridge. SECTION C505 CHANGE OF OCCUPANCY OR USE C505.1 Revise Section C505.1 as follows: C505.1 General. Spaces undergoing a change in occupancy that would result in an increase in either total modeled annual fossil fuel use or total modeled annual energy use shall comply with Sections C401.3, C402 through C406, and Section C408. Where the use in a space changes from one use in Table C405.3.2(1) or C405.3.2(2) to another use in Table C405.3.2(1) or C405.3.2(2), the installed lighting wattage shall comply with Section C405.3. Where the space undergoing a change in occupancy or use in a building with a fenestration area that exceeds the limits of Section C402.4.1, the space is exempt from Section C402.4.1 provided that there is not an increase in fenestration area. 2/14/25 225 CMR - 256.14

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Exceptions:

1. Where the component performance alternative in Section C402.1.5 is used to comply with this section, the proposed UA shall not be greater than 110% of the target UA.
2. Projects complying with C401.2 (New construction pathways)
3. Projects complying with C506 (EnerPHit standard).
4. Interior tenant fit outs having an area of 20% or less of the total building area and which do not include changes to the adjacent existing exterior wall and/or glazed wall system shall be considered Alterations per Section C503. Changes to existing punched window fenestration, when brought into compliance with Section C402.4.3 and which derate window U-value due to the fenestration to exterior wall intersection linear thermal bridge, shall not disqualify the interior fit out from this exception. Derating of the window U value shall be determined in accordance with Equation C402.7.3 where the U values shown in the equation is the U value of the window and the A total value shown in the equation is the area of the window. C505.2 Add Section C505.2 as follows: C505.2 Derating and Thermal Bridges. Existing linear thermal bridges inherent to the building structure and/or components that are not part of the planned change of use shall not be accounted for per C402.7.3. Construction documents shall include the following documentation in tabular format for these linear thermal bridges that may be excluded from vertical envelope performance:
5. Linear thermal bridge type.
6. Aggregate length of each type of linear thermal bridge.
7. Relevant detail in the construction documents showing a cross-section through the thermal bridge. C506 Add Section C506 as follows: SECTION C506 ENERPHIT STANDARD COMPLIANCE PATHWAY C506 EnerPHit Standard. This option requires compliance with Section C506.1 and C506.2. C506.1 Compliance. Buildings shall be pre-certified as meeting the EnerPHit Retrofit Plan standard using the approved Passive House certification software and program criteria by the Passive House Institute (PHI), where PHI certification is demonstrated by a PHI-accredited Certifier. C506.2 Documentation. Compliance with EnerPHit standard shall be documented in accordance with the following:
8. Prior to the issuance of a building permit, the following items must be provided to the Building Official: a. A compliance report with results from the approved Passive House certification software which demonstrates project compliance with current PHI performance requirements; b. A statement from the PHI-accredited Certifier that the approved Passive House certification software results and compliance report accurately reflect the plans submitted; c. Evidence of project registration from a PHI-accredited Certifier. OR a. A Design Certification Letter/ Design State Conditional Assurance Letter from a PHI-accredited Certifier.
9. Prior to the issuance of a final certificate of occupancy, the following items must be provided to the building official:
   1. A Design Certification Letter from a PHI-accredited Certifier.
   2. An updated compliance report with results from the approved Passive House
   certification software which reflects "as-built" conditions and test results (blower door and ventilation results) that demonstrates project compliance with PHI performance requirements; 2/14/25 225 CMR - 256.15

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued c. A copy of both the air leakage test results and report on the commission settings and performance of the building's ventilation system; d. A statement from the Certified Passive House Consultant or Certified Passive House Designer that the project test results meet the model performance requirements, all the mandatory limits and any other mandatory requirements. OR a. A Final Certification Letter from a PHI-accredited Certifier. Appendix CB Adopt unamended APPENDIX CB: Solar-Ready Zone – Commercial. APPENDIX CC - MASSACHUSETTS MUNICIPAL OPT-IN SPECIALIZED ENERGY CODE 2025 COMMERCIAL BUILDING PROVISIONS The provisions contained in this appendix are not mandatory unless specifically referenced in the adopting ordinance. The provisions contained in this appendix together with referenced sections from the Stretch energy code constitute the Specialized opt-in code for commercial buildings, and may be adopted by a city or town together with the Residential Specialized code Appendix RC as their stretch energy code. When adopted by the local municipality, the provisions in this appendix are mandatory in combination with the IECC2021 with Massachusetts Stretch code amendments. SECTION CC101 GENERAL CC101.1 Replace Section CC101 as follows: CC101.1 Purpose. The purpose of this appendix is to form the commercial building provisions of the Massachusetts Municipal Opt-in Specialized Code to supplement the Massachusetts Stretch Energy Code and to provide a compliance pathway for buildings that require renewable energy systems of adequate capacity to achieve net zero carbon. C101.2 Replace Section CC101.2 as follows: CC101.2 Scope. This appendix applies to new buildings that are addressed by the Municipal Opt-in Specialized Code. Residential buildings or dwelling units within mixed use buildings shall comply as follows:

1. New dwelling units over 4,000 sq. ft. in conditioned floor area in Mixed Fuel Buildings shall comply with the Zero Energy pathway and Section CC103 or with residential code Section RC102.
2. New R-use buildings over 12,000 sq. ft. in conditioned floor area shall comply in accordance with Table CC101.2.
3. New R-use buildings less than or equal to 12,000 square feet in conditioned floor area shall comply with Residential Appendix RC. TABLE CC101.2 MULTI-FAMILY AND R-USE COMPLIANCE R-Use buildings over 12,000 sf, or R-Use portions over 12,000 sf in mixed-use buildings Compliance Path options C407.3 Passive house C401.2.1 Prescriptive and Performance Compliance R-2 Multi-family Required N/A R-1 Occupancies (e.g. transient occupancy Hotels/Motels) Optional Options 1, 2, or 3 2/14/25 225 CMR - 256.16

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued Exceptions:

1. Detached one- and two-family dwellings and townhouses as well as Group R-2 buildings three stories or less in height above grade plane, manufactured homes (mobile dwellings), and manufactured houses (modular dwellings). These buildings and dwelling units shall comply with Residential Appendix RC under the Specialized energy code.
2. Buildings that use neither electricity nor fossil fuel. CC101.3 Add Section CC101.3 as follows: CC101.3 Compliance. New buildings shall demonstrate compliance with Sections CC101.4, CC101.5 and one of the following pathways:
3. Zero Energy pathway: Buildings shall comply with Section CC103 and demonstrate that they are Zero Energy Buildings in accordance with Equation CC-1. Mixed Fuel Buildings with any capacity for on-site fossil fuel use shall be pre-wired for future electrification of all fuel uses in accordance with Section CC105.
4. All-Electric pathway: Buildings shall comply with Section CC104.
5. Mixed Fuel pathway: Mixed Fuel Buildings other than Zero Energy Buildings with any capacity for on-site fossil fuel use shall comply with CC105 and CC106. The following uses shall be excluded when determining whether new buildings will have on- site fossil fuel use:
   1. On-site back-up power generators using fossil fuel
   2. On-site refuelling of vehicles or outdoor equipment using fossil fuels
   CC101.4 Add Section CC101.4 as follows: CC101.4 Minimum building energy efficiency. New buildings shall comply with Section C401.2.1 or C401.2.2. as prescribed in Section C401. Existing buildings shall comply with Chapter 5 as amended. CC101.5 Add Section CC101.5 as follows: CC101.5 Minimum electric vehicle ready parking requirements. New parking spaces shall provide electric vehicle ready spaces in accordance with Section C405.13 and Table C405.13. SECTION CC102 DEFINITIONS CC102 Revise Section CC102 as follows: CC102.1 Definitions. The definitions contained in this section supplement or modify the definitions in the MA amended International Energy Conservation Code, in Section C202. BUILDING ENERGY. All energy consumed at the building site as measured at the site boundary. Contributions from onsite or off-site renewable energy systems shall not be considered when determining the building energy. ENERGY UTILIZATION INTENSITY (EUI). The site energy for either the baseline building or the proposed building divided by the gross conditioned floor area plus any semiheated floor area of the building. For the baseline building, the EUI can be divided between regulated energy use and unregulated energy use. NET ZERO EMISSIONS BUILDING. A building which is consistent with achievement of MA 2050 net zero emissions, through a combination of highly energy efficient design together with being either a Zero Energy Building, or an All-Electric Building, or where fossil fuels are utilized, the building is fully pre-wired for future electrification and generates solar power on-site from the available Potential Solar Zone Area. OFF-SITE RENEWABLE ENERGY SYSTEM. Renewable energy system not located on the building project. 2/14/25 225 CMR - 256.17

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued ON-SITE RENEWABLE ENERGY SYSTEM. Renewable energy systems on the building project. POTENTIAL SOLAR ZONE AREA. The combined area of any flat roofs, or low-sloped roofs and any steep-sloped roofs oriented between 90 degrees and 300 degrees of true north where the annual solar access is 70 percent or greater. Annual solar access is the ratio of "annual solar insolation with shade" to the "annual solar insolation without shade”. Shading from obstructions located on the roof or any other part of the building shall not be included in the determination of annual solar access. RENEWABLE ENERGY SYSTEM. Photovoltaic, solar thermal, geothermal energy and wind systems used to generate energy. SEMIHEATED SPACE. An enclosed space within a building that is heated by a heating system whose output capacity is greater than or equal to 3.4 Btu/h × ft 2 of floor area but is not a conditioned space. ZERO ENERGY BUILDING. A building which through a combination of highly energy efficient design and onsite renewable energy generation is designed to result in net zero energy consumption over the course of a year as measured in MMBtus or KWh eq , on a site energy basis, excluding energy use for charging vehicles. SECTION CC103 ZERO ENERGY PATHWAY MINIMUM RENEWABLE ENERGY CC103.1 Revise Section CC103.1 as follows (keeping Table CC103.1 for climate zone 5A unchanged): CC103.1 Renewable energy. On-site renewable energy systems shall be installed to offset the building energy as calculated in Equation CC-1. REonsite $= Ebuilding (Equation CC-1) where: REonsite = Annual site energy production from on-site renewable energy systems (See Section CC103.2). Ebuilding = Building energy use without consideration of renewable energy systems, on-site energy storage, on-site back-up generators, or on-site refuelling of vehicles or outdoor equipment. When Section C401.2.1(1) is used for compliance with Section CC101.4, building energy shall be determined by multiplying the gross conditioned floor area plus the gross semi- heated floor area of the proposed building by an EUI selected from Table CC103.1. Use a weighted average for mixed-use buildings. When any compliance pathway other than Section C401.2.1 Part 1 is used for compliance with CC101.4, building site energy use shall be determined from energy simulations. CC103.2 Revise Section CC103.2 as follows: CC103.2 Calculation of on-site renewable energy. The annual energy production from on-site renewable energy systems shall be determined using the PVWatts software or other software approved by the code official. Commercial R-use buildings may comply using the Zero Energy Buildings pathways in Appendix RC by certifying that all units meet HERS 0 or lower with on-site renewable generation or by following the on-site renewable energy calculation used in the Phius ZERO certification standard when following the Passive house compliance pathway. CC103.3 Delete Section CC103.3: CC104 Add Section CC104 as follows: 2/14/25 225 CMR - 256.18

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued SECTION CC104 ALL ELECTRIC PATHWAY CC104.1 General. New all-electric buildings shall comply with Sections CC101.4, CC101.5 and with one of the following:

1. Section C401.2.1 and Section C401.4.3
2. Section C407.3 Passive house CC105 Add Section CC105 as follows: SECTION CC105 MIXED-FUEL BUILDING PATHWAY CC105.1 General. This section together with Section CC106 establishes additional minimum requirements for new mixed-fuel buildings. CC105.1.1 Biomass heating. New buildings using clean biomass heating systems may comply with this section without meeting CC105.3.1 and CC105.3.2. Buildings with any combustion equipment using biomass that does not meet the performance standards of clean biomass heating systems shall be deemed mixed-fuel buildings and shall comply with this section in full. CC105.2 Revise Section CC105.2 as follows: CC105.2 On-site Renewable Energy. New mixed-fuel buildings shall have equipment installed for on-site renewable energy with a rated capacity of not less than 1.5 W/ft² (16.1 W/m²) multiplied by the sum of the gross conditioned floor area of the three largest floors. Exceptions:
3. Where the building site cannot meet the requirement in full with an on-site renewable energy system, the building site shall install a partial system designed to utilize not less than 75% of the Potential Solar Zone Area.
4. Buildings having average ventilation at full occupancy of greater than 0.5 cfm/sf, Hospitals, and Psychiatric Hospitals, shall have equipment installed for on-site renewable energy with a rated capacity of not less than 0.5 W/ ft² (5.4 W/m²) multiplied by the sum of the gross conditioned floor area of the three largest floors.
5. Buildings interconnected to a downtown spot network portion of the electric grid, provided that the electric utility provides a statement that on-site renewable energy can not be safely interconnected. CC105.3 Revise CC105.3.1 as follows: CC105.3 Additional efficiency requirements. Additional efficiency requirements for compliance with this Section are set forth in Sections CC105.3.1 and CC105.3.2. CC105.3.1 More efficient HVAC equipment performance. Primary heating and cooling equipment shall meet the following efficiencies as applicable:
6. Space heating combustion equipment shall be rated at greater than or equal to 95 AFUE.
7. All refrigerant-based air conditioning equipment shall be a heat pump with greater than or equal to 8.1 HSPF2 rated heating performance and greater than or equal to 15.2 SEER2 rated cooling performance for ducted systems, and greater than or equal to 8.5 HSPF2 rated heating performance and greater than or equal to 16 SEER2 rated cooling performance for ductless systems.
8. Ground source heat pump systems shall be rated at greater than or equal to 3.5 COP at design temperature. For multiple cooling systems, all systems shall meet or exceed the minimum efficiency requirements in this section and collectively shall be sized to serve 100% of the cooling design load. For multiple heating systems, all systems shall meet or exceed the minimum efficiency requirements in this section and collectively shall be sized to serve 100% of the heating design load. Exception: Clean biomass heating systems used as the primary heating system. 2/14/25 225 CMR - 256.19

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued CC105.3.2 Reduced energy use in service water-heating option. The hot water system shall meet one of the following efficiencies:

1. Greater than or equal to 82 EF combustion equipment service\water-heating system.
2. Greater than or equal to 2.0 UEF electric service water-heating system.
3. Greater than or equal to 0.4 solar fraction solar water-heating system.
4. Clean biomass heating system supplied water-heating system. Exception: Space and service water heating uses provided by a district energy system subject to a district energy system order of conditions in good standing from the Commonwealth of Massachusetts Department of Energy Resources. CC106 Add new Section CC106 as follows: SECTION CC106 WIRING FOR FUTURE ELECTRIFICATION CC106.1 Additional electric infrastructure. All combustion equipment and end-uses shall be installed in accordance with this section. Capacity for the future electric circuits required in this section shall be included in the load calculations of the original installation of electric service to the building, and each dwelling unit for R-use buildings or portions thereof. Exception: Space and service water heating uses provided by a district energy system subject to a district energy system order of conditions in good standing from the Commonwealth of Massachusetts Department of Energy Resources. CC106.1.1 Electric infrastructure for dwelling and sleeping units. Combustion equipment and end-uses serving individual dwelling units or sleeping units shall comply with Section RC104.3 Electric Readiness. CC106.1.2 Combustion water heating equipment. Gas-fired or oil-fired water heaters with a capacity less than 300,000 Btu/h (88 kW) shall be installed in accordance with the following:
5. A dedicated 208/240-volt branch circuit with a minimum capacity of 30 amps shall terminate within 3 ft. (914 mm) from the water heater and be accessible to the water heater with no obstructions. Both ends of the branch circuit shall be labeled with the words "For Future Heat Pump Water Heater" and be electrically isolated,
6. A condensate drain that is no more than 2 inches (51 mm) higher than the base of the installed water heater and allows natural draining without pump assistance shall be installed within 3 ft. (914 mm) of the water heater,
7. The water heater shall be installed in a space with minimum dimensions of 3 ft. (914 mm) by 3 ft. (914 mm) by 7 ft. (2134 mm) high, and
8. The water heater shall be installed in a space with a minimum volume of 700 cu. ft. (20,000 L) or the equivalent of one 16-inch (406 mm) by 24-inch (610 mm) grill to a heated space and one 8 inch (203 mm) duct of no more than 10 ft. (3048 mm) in length for cool exhaust air. CC106.1.3 Cooking ranges, ovens and cooktops. An individual branch circuit outlet with a minimum rating of 250-volts, 40-amperes shall be installed within 3 ft. of each gas or propane range or any permanently installed combustion equipment oven or cooktop. Exception: Commercial kitchens for cafeteria, restaurant or commercial catering business use. CC106.1.4 Clothes Dryers. An individual branch circuit outlet with a minimum rating of 250-volts, 30-amperes shall be installed within 3 ft. of each gas or propane clothes dryer. Exception: Commercial drying equipment used for manufacturing and process loads 2/14/25 225 CMR - 256.20

225 CMR: DEPARTMENT OF ENERGY RESOURCES 23.00: continued CC106.1.5 Other combustion equipment. Combustion equipment not covered by Sections CC106.1.1 and CC106.1.4 and within buildings having average ventilation at full occupancy of 0.5 cfm/sf or less shall be provided with conduit that is continuous between a junction box located within 3 ft. (914 mm) of the appliance or equipment and an electrical panel. The junction box, conduit and bus bar in the electrical panel shall be rated and sized to accommodate a branch circuit with sufficient capacity for an equivalent electric appliance, equipment or end use with an equivalent equipment capacity. The electrical junction box and electrical panel shall have labels stating, "For future electric equipment". CC106.1.6 Other combustion equipment, highly ventilated buildings. Combustion equipment not covered by Sections CC106.1.1 and CC106.1.4 and within buildings having average ventilation at full occupancy of greater than 0.5 cfm/sf shall comply with Section CC106.1.6.1 through CC106.1.6.5. CC106.1.6.1 HVAC Design and Installed Associated Electric Service. An all-electric HVAC retrofit design shall be prepared by the HVAC engineer for approval by the authority having jurisdiction. The electric service installed with the building shall be sufficient to accommodate the all-electric HVAC retrofit design. The contract documents shall show future replacement of combustion equipment based HVAC system with an equivalent all-electric system. Contract documents shall show combustion equipment to be replaced, future electric equipment, supporting electric, structural, and architectural infrastructure to be installed during building construction, and space allotments for future equipment. CC106.1.6.2 Heating, Ventilation, and Air Conditioning (HVAC) Compatibility. HVAC design shall ensure that air, water, or other systems serviced by combustion equipment can also be serviced by future electric retrofit equipment without having to upgrade, alter, or update such systems. CC106.1.6.3 Equipment Efficiencies. Electric retrofit equipment used for space and water heating shall conform to Section C401.4.3. CC106.1.6.4 Installed Infrastructure. Infrastructure shall be installed as part of building construction to accommodate future electric retrofit in order to minimize cost and disruption during retrofit. Infrastructure to be installed as part of the building construction shall include, but is not limited to, power infrastructure to building to accommodate future electric retrofit system, electric service to future distributed equipment within the building, conduits to accommodate controls to future distributed equipment within the building, and structural and architectural elements to accommodate future retrofit equipment. CC106.1.6.5 Space for Future Retrofit Equipment. Interior and exterior space shall be allotted to accommodate all future electric retrofit equipment. Where interior or exterior allotted space exceeds the space used for combustion equipment to be replaced, and/or does not correspond to the combustion equipment locations to be replaced, such space shall be set aside and may not be used for any other purpose. Signage, labels, and borders shall be used to prominently display areas and limits set aside for future equipment to prevent encroachment. REGULATORY AUTHORITY: M.G.L. c. 25A, § 6; St. 2021, c. 8. 2/14/25 225 CMR - 256.21