Fossil Fuel Free Demonstration Program

Lexington is going fossil fuel free as part of the Municipal Fossil Fuel Free Demonstration Program.


The Municipal Fossil Fuel Free (FFF) Building Demonstration Program was announced by the Massachusetts Department of Energy Resources (DOER) in 2022. This pilot program was created to establish a demonstration project where municipalities can adopt and amend general or zoning ordinances or bylaws that require new building construction or major renovations to be fossil fuel-free. More information can be found at

Why No Fossil Fuels?

In Lexington, 73% of our greenhouse gas emissions come from buildings. Much of that is driven by fossil fuel systems used to heat and cool our homes and businesses. By participating in the Demonstration Program, Lexington is ensuring that new and renovated buildings won't use fossil fuels, will be healthy environments for occupants, and won’t require costly retrofits down the line. This strategy is crucial to the successful achievement of local and regional GHG reduction goals.

Lexington’s Bylaw

Lexington passed its own Fossil Fuel Free bylaw in order to participate in the Demonstration Program. The bylaw goes into effect on March 21, 2024 (90 days after Lexington was accepted into the Demonstration Program by the Department of Energy Resources). 

Note: Following recommendations from the Department of Energy Resources (DOER), Lexington staff are bringing two proposed amendments to Town Meeting in spring of 2024. If approved, these changes would go into effect on January 1, 2025. Differences between the original bylaw and the proposed amendments are noted in red italics. See below for the details of the proposed amendments.

What projects does the bylaw apply to?

The bylaw applies only to new construction (including accessory buildings) and all major renovations where over 50% of the home is renovated (gut jobs). Starting January 1, 2025, the bylaw will likely also apply to residential additions or changes of use over 1,000 square feet, commercial additions or changes of use over 20,000 square feet, and commercial and residential additions over 100% of the conditioned area of the existing building. 

What is prohibited?

No building permits will be issued by the Town for new construction or major renovations that include the installation of new on-site fossil fuel infrastructure. This includes piping for coal, natural gas, or other fossil fuels in a building, within the property lines of a premise, or connecting a supply tank to a building.

Are there exemptions?

Yes. The bylaw does not apply to:

  1. Research laboratories for scientific or medical research
  2. Hospitals and medical offices
  3. Piping required to fuel back up generators, indoor or outdoor cooking appliances, indoor or outdoor fire or fire features, or appliances for outdoor heating. Starting January 1, 2025, indoor cooking appliances and indoor fire features are likely to be prohibited.
  4. Multi-family buildings over 12,000 square feet that utilize gas or propane for domestic water heating as the only combustion equipment (permit application must be filed prior to January 1, 2027 for this exemption)
  5. Buildings heated with clean biomass heating systems as the only combustion equipment
  6. Utility service piping connecting the grid to a meter or to a gas meter itself
  7. The extension or modification of heating systems or the modification of radiator, steam, or hot water piping (as long as no new fossil fuel piping is installed)
  8. Repairs of any existing portions of a fuel piping system deemed unsafe by the Plumbing and Gas Inspector

Frequently Asked Questions

Yes. The Building Commissioner can grant a waiver if applicants can prove that compliance with the bylaw makes a project financially infeasible or impractical to implement. All waiver request must be supported by a detailed cost comparison, including available rebate and credits. Waivers may be granted for specific portions of a project, rather than entire projects. The Building Commissioner’s decision on granting a waiver can be appealed to the Select Board within 30 days of receiving the decision.

Proposed Amendments (Effective January 1, 2025 if approved)

The proposed amendments going to Town Meeting in the spring of 2024 would:

  1. Remove the exemption for indoor cooking appliances and indoor fireplaces. Fossil fuel cooking and fire features would no longer be permitted in new construction and major renovations under the bylaw.
  2. Update the definition of a “Major Renovation” to include:
    • Low-rise residential additions over 1,000 square feet and additions exceeding 100% of the conditioned floor area of the existing dwelling unit, 
    • Additions over 20,000 square feet and additions that exceed 100% of the conditioned floor areas of the existing building for all building use types except low-rise residential, 
    • Level 3 Alterations as defined in the International Existing Building Code (IEBC 2021) (which exceed 50% of the existing conditioned floor area) exceeding 1,000 square feet for low rise residential, or exceeding 20,000 square feet for all other building uses, or 
    • Change of use of over 1,000 square feet per International Energy Conservation Code (IECC 2021) Sections R505, or 
    • Change of use of over 20,000 square feet or change of use of 100% of the conditioned floor areas of the existing building for all building use types except low-rise residential, International Energy Conservation Code (IECC 2021) Sections C505.


Starting in 2019, several communities in Massachusetts passed local bylaws that would allow them to restrict the use of fossil fuels in new development. Ultimately, the Massachusetts Attorney General’s Office did not approve these bylaws because state regulations such as the Building Code preempt local bylaws. After this ruling 10 communities passed Home Rule Petitions, asking the state for the authority to restrict the use of fossil fuels. The 10 communities were:

  • Acton

  • Aquinnah

  • Arlington

  • Brookline

  • Cambridge

  • Concord

  • Lexington

  • Lincoln

  • Newton

  • West Tisbury

As a response to these petitions, the 2022 State Climate Act required the Massachusetts Department of Energy Resources (DOER) to establish a demonstration project under which 10 cities and towns are allowed to adopt or amend general or zoning ordinances/bylaws that require new building construction or major renovation projects to be fossil-fuel free. The FFF Demonstration Program is the result of those efforts, and the 10 communities that submitted Home Rule Petitions have been prioritized for acceptance into the program.