The specialized code applies to new construction only. There is no impact on additions or renovations to existing buildings.

For all categories of buildings, fossil fuel (“mixed fuel”) is still a valid option.  However, by choosing to connect fossil fuels to the building, some additional criteria must be met in order to partially or fully offset the emissions impact using onsite renewable energy (typically solar) and pre-wiring to enable an easy transition to all electric in the future. Although the easiest and least expensive way to meet the code is to build all electric construction, the mixed fuel path can be selected if, for instance, a gas stove is important to the home buyer.

The specialized code applies Appendix RC (residential) to 225 CMR 22 and Appendix CC (commercial) to 225 CMR 23. The stretch code is still fully applicable, but the additional compliance details from the specialized code are also applied.

See the following table for more detailed description of the options available to builders.

Compliance pathways for builders

Building size	Fuel type	Minimum efficiency	Electrification	Onsite solar
Home less than 4000 sq. ft.	All electric	Follows stretch code (July 2024) HERS 45	Full	Optional
	Mixed fuel	Follows stretch code (July 2024) HERS 42	Pre-wiring	Solar (except shaded sites)
Home greater than 4000 sq. ft.	All electric	Follows stretch code (July 2024) HERS 45	Full	Optional
	Mixed fuel	HERS 0 (HERS 42 + solar) or Phius Zero	Pre-wiring	Solar
Multi-family home greater than 12,000 sq. ft.	All electric	Passive house	Full	Optional
	Mixed fuel	Passive house	Pre-wiring	Optional
Commercial	All electric	Follows stretch code	Full (excludes manufacturing processes)	Optional
	Mixed fuel	Follows stretch code	Pre-wiring	Solar (except shaded sites)