Frequently Asked Questions

The design and construction of buildings in Massachusetts is governed by state law. Energy conservation codes establish requirements for energy efficiency. Their intent is to reduce emissions throughout the lifetime of a building.

Massachusetts currently offers communities three choices of stringency in its building energy codes: the Base Code, the Stretch Code, and the Specialized Code.

• The Base Energy Code defines minimum design and construction requirements for energy efficiency.

• The Stretch Energy Code provides a more energy efficient alternative to the base energy code.

• The Specialized Code builds on the Stretch Code through additional clean energy measures.

As part of the Green Communities Act of 2008, Massachusetts is required to update its building code every three years to be consistent with the most recent version of the International Energy Conservation Code (IECC). This ensures that new buildings are designed and constructed with energy efficiency in mind. The current Base Code in Massachusetts, effective January 1, 2023, consists of IECC 2021 with additional Massachusetts-specific amendments. Fewer than 8% of Massachusetts residents live in Base code communities.

In 2009, Massachusetts adopted an above-code appendix to the Base Code — the Stretch Code — which emphasizes energy performance and is designed to result in cost-effective and energy-efficient construction. This performance-based approach brings in third-party verification, which protects homeowners by ensuring that buildings perform as designed. The Stretch code also has ventilation requirements that include energy recovery systems. The newest phase of updates, incorporating 2021 IECC standards and new guidance, became effective on February 14th, 2025, for both low-rise residential and commercial buildings, building on the 2023 changes. 

As of today, roughly 300 of Massachusetts’ 351 municipalities have adopted the Stretch Code. 

Medfield adopted the Stretch Code at its Annual Town Meeting on April 25th, 2016. 

The Massachusetts Climate Act of 2021 required the development of a new Municipal Opt-in Specialized Energy Code. The Specialized Code consists of IECC 2021 with Massachusetts-specific amendments plus additional Stretch Code and Specialized Code amendments. Its purpose is to ensure that new construction is consistent with a net-zero Massachusetts economy in 2050. The code adds new energy efficiency requirements for mixed-fuel residential and commercial buildings (i.e., buildings that include fossil fuels). There are relatively few changes from the Stretch code and these center around consumer protection — saving people money and unnecessary work to comply with future building code requirements.

• The Specialized Code applies only to new construction, not to existing buildings. There are no additional requirements for additions, alterations, or renovations.

• The Specialized Code adds consumer protection requirements for new buildings that use fossil fuel. For example, mixed-fuel buildings must pre-wire any fossil fuel systems or appliances for later conversion to electricity. During construction, when walls are open, wiring for later transition to all-electric is not difficult and avoids costly retrofits later.

• New homes with fossil fuel will have to install a minimum amount of solar (with some exceptions for shading) to reduce utility costs.

• Homes over 4,000 square feet must install enough solar or other renewables to fully offset the home’s energy use.

• New multi-family housing construction that is over 12,000 square feet will need to meet low-energy-use “Passive House” standards.

• There are no additional requirements for all-electric new construction.

Detailed explanations and more frequently asked questions can be found at the Commonwealth of Massachusetts’s Building Energy Code website.

• If Medfield opts to adopt the Specialized code, it could qualify to join the "Climate Leader Communities" program which gives access to additional funding. To date, Medfield has received over $660,000 in grants for building and equipment upgrades and replacements under the Green Communities program.  These grants are extremely competitive as we saw in the last cycle where Medfield did not receive grant funding, and the types of projects and amounts are limited. Enhanced funding under the Climate Leaders program includes $150,000 in technical grants and up to $1M per 3-year cycle for an extended range of projects including solar installations or an energy manager position. For example, Medfield is working to officially close the landfill, and a large municipal solar array is one of the potential future uses being discussed. A CL grant could also help fund energy efficiency measures at the new school such as heat pumps or a solar array. To date, 28 communities - that is HALF of the Specialized Code Communities, have entered into this Climate Leader program. In 2025, four Climate Leader communities have been awarded a total of $3.7M. https://www.mass.gov/news/healey-driscoll-administration-certifies-nine-new-climate-leader-communities   

In this cycle, MA has set aside $60M in funding for the Climate Leaders program https://www.mass.gov/news/healey-driscoll-administration-designates-three-new-green-communities-announces-60-million-climate-leader-grant-funding 

• In 2021, Medfielders voted to adopt a Net Zero 2050 Goal for the town.  Adopting the Specialized code would ensure that new buildings in Medfield are highly energy efficient and help the town reach that goal.

No, the Specialized Code applies to new construction only.

No, the Specialized Code applies to new construction only.

No, the Specialized Code provides the flexibility to build homes and commercial buildings with mixed fuels (e.g., electric and natural gas).  However, homes with fossil fuels would need to meet additional requirements such as pre-wiring for electrification and installation of solar (with some exceptions).  

Yes, but a mixed-fuel building must meet the mixed-fuel requirements, including installation of electrical service and wiring for eventual conversion of those gas appliances to electric. 

Generators powered with fossil fuels are allowed in all-electric homes under the Specialized Code. Whole-home backup batteries are an option as well. In addition, homes built to meet the higher insulation and air sealing standards of the Stretch and Specialized Codes will maintain comfortable conditions indoors for longer periods of time than conventionally built homes.

• If the home is all-electric and less than 4,000 square feet, there are no requirements beyond the Stretch Code. 

• If the mixed fuel pathway is chosen, the builder would incur additional costs to pre-wire for future electrification. This would be an added cost to the builder but would save the homeowner from the burden of a costly future retrofit. In addition, solar panels would need to be installed, again at a cost to the builder but a benefit to the homeowner. Solar panels are not required if the home is too shady.

• All-electric homes are generally cheaper to build than homes with fossil fuel, as the heat pump replaces both central air conditioning and (typically) a gas furnace. Also, the expense of running a gas line to the home would be avoided.  In addition, MassSave provides rebates of $15,000 to builders for hitting a Home Energy Rating System score of 45, and $25,000 for meeting HERS 35 or Passive House.

• A home greater than 4,000 square feet and heated with fossil fuels, on the other hand, would be more costly to construct due to the enhanced efficiency measures required and the need to add a separate air conditioning system.

• More details on cost and benefits can be found in the DOER presentation to the Selectboard starting at 1:29:40hrs. 

The Specialized Code only applies to new construction, so it won’t impact individuals purchasing an existing home. 

The financial impact to persons purchasing a newly constructed all-electric home is anticipated to be minimal.  

• The Specialized code doesn’t impose any new requirements for all-electric homes relative to the existing Stretch Code.  

• All-electric homes are generally cheaper to build.  

• In addition, MassSave provides generous rebates to builders for meeting the code requirements.  

A home greater than 4,000 square feet with fossil fuels would be somewhat more costly to construct but would have added energy efficiency likely to lower operating expenses.

A heat pump uses technology similar to that found in a refrigerator or an air conditioner, only it works both to heat and cool the home. In heating mode, it extracts heat from a source, such as the surrounding air or geothermal energy stored in the ground transfers the heat to where it is needed. When cooling, it transfers the heat from your home to the outside.. Because most of the heat is transferred rather than generated, heat pumps are far more efficient than conventional heating technologies such as boilers or electric heaters and can be cheaper to run. The output of energy in the form of heat is normally several times greater than that required to power the heat pump, normally in the form of electricity. For example, the coefficient of performance (COP) for a typical household heat pump is around four, i.e. the energy output is four times greater than the electrical energy used to run it. This makes current models 3‐5 times more energy efficient than gas boilers. (from https://www.iea.org/reports/the-future-of-heat-pumps/how-a-heat-pump-works). 

In the near term, homeowners in newly constructed, all-electric homes will likely pay more to heat their homes with electric heat pumps than with natural gas.  However, within the next decade, the cost of heating with natural gas is anticipated to increase relative to electricity as more people electrify their homes and fewer people remain to support the costs of the gas infrastructure.  

Eversource is now offering a winter heating Heat pump rate that lowers electricity bill by about 23%.  Heating with fuel oil, propane, and electric resistance heat is generally more expensive than heating with electric heat pumps.  

Medfield also has a municipal aggregation program, Medfield Community Electricity (MCE), with new electricity supply options that provide more renewable energy and stable prices for all Medfield residents and businesses. The program is a town-vetted alternative to Eversource’s default supply and other third-party electricity suppliers. MCE can provide lower-cost electricity for those who sign up.  

Yes. Eversource, the electricity provider for Medfield, has filed plans to increase grid capacity by 180% to support “full electrification” and a “greener grid” by 2050.

Today, the electric grid is operating at 20% below the all-time system electric peak in 2006, due to energy efficiency measures. While switching from fossil fuels to electric vehicles, electric heat pumps, and electric appliances will increase demand on the regional grid and the local electric distribution system, electrification will result in nearly 50% greater energy efficiency overall. For example, electric heat pumps are 2.5 to 4 times more efficient than the most efficient gas boiler. Stricter insulation and air sealing requirements under the Stretch and Specialized codes will reduce the electric demand of new buildings.  By 2035, building electrification is predicted to cause the grid to switch from summer peaking to winter peaking; this change will not require significant infrastructure upgrades.

Under the Specialized code, in new construction buildings that opt to use fossil fuels, solar panels must be installed (with allowances for shading). This will increase renewable energy supply to the grid during peak summer demand and increase the resilience of the electricity grid.

No, because financial incentives through MassSave and competitive incentives from the Department of Housing and Community Development make development of affordable housing attractive including incentives to meet the Specialized Code. All-electric buildings result in little, if any, additional construction costs. And third-party power purchase agreements can provide solar energy with no upfront cost. 

Recent analysis of housing development in Massachusetts indicates that stronger energy codes correlate with more home building overall. Specialized code communities have added new housing 17% faster than Stretch code communities. Stretch code communities in turn have added new housing 14% faster than Base code communities.  https://phmass.org/2025/12/30/codes-and-housing-supply/ 

Yes, these developments must comply with all applicable building codes, including the Specialized Code.

High-efficiency net-zero municipal buildings are becoming standard practice in comparable communities across the Commonwealth. With a combination of incentives from MassSave and other funding sources, net-zero municipal buildings are often more cost effective to build and maintain over the lifecycle of the building in comparison to conventional and/or mixed fuel buildings. 

As an example, let’s compare some of our existing municipal buildings with new, fully electric ones built to the Specialized code. The energy use of a building is often expressed as the Energy Use Intensity (EUI), which is its energy use per floor area, like Btu/sqft. The higher the EUI, the less efficient the building is and the more energy it uses. The Dale Street school has an EUI of 106, the Public Safety Building’s is 105, Blake as an EUI of 90.  In contrast, the new Lexington High School is designed for an EUI of 25, close to Passive House standards, so it will use about a quarter of the energy per sf as our conventional buildings. Lexington expects to save hundreds of thousands in energy bills over its lifetime, and if you include the battery storage and solar that are planned to be added, they predict millions in savings. Westwood’s new K-5 elementary school, Pine Hill, was also designed for an EUI of 25, but with careful procedures is now operating at an EUI of 18-19.  This is expected to be reduced to an EUI of 7-8 once the school’s solar array is turned on. 

While it is too early to predict what design the Medfield School Building Committee will decide on for the new Dale Street school, the standard for new school buildings in Massachusetts now is typically all-electric or net-zero energy, with some new schools even achieving triple net-zero (energy, water, waste). The MSBA offers a 3-point adder to funding new school building if they are all-electric, and MassSave incentives also lower construction costs for all-electric buildings. A highly efficient ground-source heat pump system would qualify for a 30% federal rebate, further reducing up front cost and long-term operating cost.

• Residential: Single family, two-family, townhouses, and buildings three stories or less in height above grade.

• Commercial: Assembly, business, educational, institutional, mercantile, factory and industrial, storage, high hazard, utility, and miscellaneous; buildings four stories or more in height above grade.

• 56 communities representing over 32% of the State’s population have adopted the Specialized Code. 

• Metrowest communities — many of them Medfield’s neighbors — that have already adopted the Specialized Code include among others Ashland, Dedham, Framingham, Hopkinton, Milton, Natick, Needham, Norwood, Sharon, Sherborn, Wayland, Wellesley, and Weston. https://www.mass.gov/doc/building-energy-code-adoption-by-municipality/download 

• Several more communities have plans to adopt the Specialized Code in spring and fall 2026. 

The Sponsors of Mass Save provide valuable compliance training, technical support, and documentation tools for building industry stakeholders. Building energy code compliance training sessions are available for all Massachusetts code officials and building professionals. Medfield building officials have already benefitted from such training in 2025.

The Sponsors of Mass Save, in partnership with Passive House Massachusetts, have launched a Passive House and All-Electric Homes Training offer to support workforce development and market transformation in the energy efficiency and building construction industries.

Another organization offering education is the Passive House Network. Founded in 2011, the Network is a national 501(c)3 nonprofit that provides education and community to building industry professionals specifically focused on the rapid implementation of Passive House building standards.

No. The rooftop solar requirement for new homes in the Specialized Code provides exemptions where solar access is less than 70% or the roof is too steep.

• New homes do not necessarily need a 400-amp panel. This is because all-electric homes built to the new code have dramatically lower peak heating loads than conventionally built homes. 

• Large new homes are likely already incorporating 400-amp panels due to their size, so no additional upgrades above existing standard practice are required.

• The main increase in electrical demand is the EV-ready requirement at 50 amps for a single-family home, which is not a new requirement or the Specialized code, but already part of the current Stretch code.

The building inspector will continue to be responsible for building code enforcement. Passive House certification (e.g. for large multifamily buildings) is independently obtained and does not require additional knowledge or training of the building inspector.

A HERS rating test can be performed on ADUs whether they are attached or not. The Stretch code and the Specialized code have the same HERS limits. 

No, it would be subject to the existing Stretch Code; the Specialized code has no provisions for additions or renovations. If a home is destroyed for example by fire, and if the restored home is built on the same footprint, it would not normally be considered new construction.  But if the new home is built on an entirely new footprint, it may be considered new construction. The ultimate decisions on what is considered new construction is taken by the local Building Inspector.

The up-front cost of the solar panels is expected to be less than 1% of the cost of a new home.  The average payback period is roughly 5-7 years, and for the rest of the typical 25-year life of the panels they would be reducing the homeowner’s electric bill.

The Specialized Code is not prescriptive in this regard, and the location of the wiring would be up to the building inspector.  For an appliance, the wiring would typically terminate in a plug located near the existing fossil fuel appliance.  For a heat pump replacing a boiler or furnace, the wiring would likely terminate in the basement.  

Construction time depends on a large number of factors. The Specialized code is not expected to affect construction time.

Any new large multi-family housing construction (>12,000 sf) will need to meet highly energy efficient (i.e. low energy use) Passive House standards. Passive House buildings are already being done more and more for affordable housing throughout Massachusetts, even in communities where it is not mandated. According to developers (see this recording and this slide deck) these are some reasons why:

• straightforward and easily implemented standards, with independent verification (no additional knowledge or training needed by Building Inspectors)

• results in significantly lower total life cycle costs and minimal additional construction costs - also see the “Safe at Home” report 

• ensures healthier, more comfortable, more resilient, and more equitable multi-family housing, including the health benefits of excellent ventilation and indoor air quality free of the harmful and carcinogenic gases produced by gas appliances

• small to no cost differential, particularly with experience teams - developers say that there are much bigger cost drivers for their projects including:

  • Parking minimums

  • Lack of multi-family zoning

  • Onerous design requirements

  • Delays in permitting time 

• aligns with community values and climate goals

• avoided health costs of burning fossil fuels

• eligible for significant upfront incentives from MassSave.

• The Department of Housing and Community Development also has a Low Income Housing Tax Credit program that gives extra points for both Passive House and for electrification.

Recent analysis of overall housing development indicates that Specialized code communities are adding new housing faster than Stretch code communities, and that Stretch code communities in turn are adding more new housing faster than Base code communities.  https://phmass.org/2025/12/30/codes-and-housing-supply/

• Another FAQ can be found at the Department of Energy Resources (DOER) website at https://www.mass.gov/doc/stretch-energy-and-municipal-opt-in-specialized-building-code-faq/download

• A recording of the DOER presentation of the Building Energy codes to the Medfield Select board is available at the Medfield TV YouTube channel at 1:12hrs at https://www.youtube.com/watch?v=XYfjDHiphKA&list=PLypOllJHc4M1mT8vN-WUuIe29PmvAG619&index=13&t=6003s

• For current information and updates, please visit the Energy Committee site https://www.town.medfield.net/2308/Specialized-Code and follow us at on Facebook at https://www.facebook.com/search/top?q=medfield%20energy%20committee