Massachusetts has put forward changes to its building energy code that aim to increase all-electric new home construction and virtually eliminate heating load in commercial buildings.

The Massachusetts Department of Energy Resources, or DOER, on Feb. 8 proposed updating an optional energy code used by 85% of Bay State towns and cities. The updates do not prohibit natural gas hookups in new buildings but incentivize builders to opt for electric heat pumps instead.

The changes stem from 2021 legislation that required Massachusetts to reduce greenhouse gas emissions by at least 50% below 1990 levels by 2030. The state is seeking to achieve net-zero economywide emissions by 2050.

"That means that we need to move forward with integrating the most cost-effective climate solutions into new construction today and ensure that those buildings are 2050 compliant," DOER Commissioner Patrick Woodcock said during a Feb. 8 virtual presentation.

The 2021 law also required DOER to update the state's existing stretch energy code — which "stretches" beyond the base code — and develop a third, even more stringent option for cities and towns.

The mandate for DOER to create the new, highly efficient code represented a compromise between Gov. Charlie Baker and representatives of municipalities that have sought authority to ban new natural gas hookups since 2019.

DOER estimated the proposal would result in $21 billion in combined construction and operating cost savings and reduce greenhouse gas emissions by 694,000 tons per year by 2035.

Building electrification is key pathway

The DOER proposals are based on studies commissioned in 2019 to analyze potential building code standards that would be appropriate for Massachusetts' climate. Those studies analyzed upfront and ongoing costs and focused on fossil fuel use and emissions from buildings — representing a shift from the historical code-making focus on total building energy needs, according to Maggie McCarey, director of DOER's Energy Efficiency Division.

"One of the key considerations and findings of these studies is the importance of electrification to achieve emissions reductions from new construction," she said. "Efficiency must be first, but we also have to start shifting our new construction to electric and electric-ready."

Currently, Massachusetts towns and cities can follow either the state's base energy code or its stretch energy code. Adopted in 2008, the stretch energy code aims to minimize a building's lifecycle energy cost through more stringent energy efficiency and water conservation, as well as through renewable and alternative technologies. Today, 299 of Massachusetts' 351 municipalities follow the stretch energy code, McCarey said.

Under both codes, homes qualify for state and federal incentives if they achieve a Home Energy Rating System, or HERS, score of 55 or lower. The system measures homes on a per unit basis, compared to a 2006 baseline equivalent to a HERS score of 100. The average HERS score for new homes in Massachusetts is 51.

Small residential buildings face tougher performance targets

The DOER on Feb. 8 proposed tightening performance standards for one- or two-family homes, townhomes and some low-rise multifamily buildings. To qualify for incentives under the existing stretch code, all-electric construction would have to achieve a HERS score of 45, while buildings heated with fossil fuels would need a 42, starting in December 2023.

The analysis found that homes were cost-effective to build and significantly cheaper to operate with a HERS score of 42. That score also represents the tipping point at which electric heat pumps overwhelmingly save builders and occupants money compared to fossil fuel furnaces. To give heat pumps another leg up, the DOER gave them a three-point HERS advantage.

Building all-electric in the updated stretch energy code will likely be sufficient to achieve a 45 HERS score, because heat pumps are more efficient than gas furnaces, DOER Energy Efficiency Division Deputy Director Ian Finlayson said. Hitting a 42 HERS score in construction with fossil fuel hookups will require additional interventions, such as triple-glazed windows, better insulation, improved air sealing or heat recovery, he said.

A new specialized opt-in stretch energy code proposed by DOER would create a third option for towns and cities. It would incorporate the same requirements, but with added conditions for homes that use fossil fuels. Those homes would have to install on-site solar panels where feasible and include electrical wiring needed for easy conversion to electric systems. DOER proposed the same solar and electric-ready requirements for commercial buildings.

Both stretch code proposals would require single-family homes to be wired for one electric vehicle parking space. The existing stretch code and specialized opt-in code would require setting aside 10% and 20% of spaces in multifamily building lots for EVs, respectively.

Commercial building code 'almost eliminates' heating needs

For updates to the stretch energy code for commercial buildings, DOER focused on finding ways to significantly reduce heating loads by improving building envelopes and energy recovery.

"For most buildings, the heating loads in our proposed code will be on the order of 90% smaller than our current code," DOER Efficiency Engineer Paul Ormond said. "It's not an exaggeration to say our proposed code almost eliminates heating of commercial buildings."

The updated stretch code includes five pathways for achieving compliance, but many buildings would be subject to a single, newly established pathway. Developers would use modeling to demonstrate proposed buildings can operate within certain heating and cooling limits. Doing so makes it easier to electrify the building, a "key goal" for DOER, Ormond said.

For the new specialized opt-in stretch energy code, DOER proposed phasing in passive house requirements for large multifamily buildings through 2024. Passive house is a design approach that prioritizes rigorous efficiency, a tight building envelope and other principles to drive down heating and cooling needs. Achieving passive house status — which equates to a HERS score of about 34 in Massachusetts — is another compliance pathway in the residential and commercial building codes.

DOER plans to host a series of stakeholder engagements and faces a deadline to release the specialized opt-in code by December 2022. To ease implementation, the department said it will aim to make all three code options effective by January 2023.