Buildings & Development

Sustainable Development

Lexington uses state buildings codes, Town bylaws, and other regulations to promote the development of sustainable and resilient buildings that are healthy and affordable for occupants. The Lexington Sustainable Development Guide provides developers and builders with the information they need about sustainable building requirements and supports to meet the requirements.

Building Energy Codes

In Massachusetts, municipalities have a choice of three energy codes to enforce.

  1. The base code builds off of the International Energy Conservation Code with Massachusetts-specific amendments.
  2. The stretch code builds off the base code with stricter energy efficiency standards. It is required for all Green Communities and around 300 communities use it.
  3. The specialized code is even more stringent code than the stretch code and communities can choose to opt in to use with a Town Meeting vote. It was developed in 2022 after a state climate bill called for the creation of a “net zero” building code.

Code Status in Lexington

Lexington adopted the stretch code in 2010. Recent updates to the stretch code automatically went into effect on January 1, 2023. Lexington Town Meeting passed the specialized code in March 2023, with an effective date of January 1, 2024. The Buildings Department enforces the codes.

To learn more about the updated stretch code and the specialized code, consult the resources below.

Benefits of the Specialized Code


  • All-electric and zero-energy buildings are encouraged, driving new construction closer to net zero emissions. 
  • Buildings using fossil fuels must offset usage with onsite solar and must be pre-wired for future electrification. 
  • The energy efficiency requirements of the specialized code result in lower heating and cooling loads in new buildings.


  • The specialized code encourages upfront electrification, helping building owners avoid inevitable costly retrofits down the road.
  • Heating with ground-source or air-source heat pumps in Massachusetts is less expensive than heating with oil or propane. The Applied Economics Clinic found that it will become less expensive than heating with gas, as early as 2026.
  • The vast majority of net zero projects that already exist in Massachusetts experienced a premium cost increase of less than 1%.
  • Forgoing gas hookups in new buildings can save developers thousands of dollars per building.


  • In Massachusetts, buildings are the second most significant source of air-pollution-related premature deaths. Buildings without fossil fuel hookups reduce pollution, both inside and outside.
  • Children living in homes with gas cooking stoves have a 42% higher risk of asthma. The specialized code encourages the use of electric or induction stoves.