Massachusetts Is About to Make Spray Foam Insulation Much Harder to Justify

Massachusetts is developing embodied carbon requirements that will fundamentally change which insulation materials make financial sense for multifamily construction. Closed-cell spray foam, one of the most commonly specified insulation materials, has one of the highest embodied carbon footprints in the industry.

If you are designing a project today that will be permitted in 12 to 18 months, the materials you specify now may face penalties under rules that are actively being developed.

What Embodied Carbon Rules Mean

Current energy codes focus on operational energy: how much energy the building uses once it is occupied. Embodied carbon is different. It measures the carbon emissions associated with manufacturing, transporting, and installing building materials.

A building can have excellent operational energy performance (low HERS score, efficient systems) while still having a massive carbon footprint from the materials used to build it. Embodied carbon rules address that gap.

Massachusetts is among the first states to incorporate embodied carbon into building codes. The specific mechanism is still being finalized, but the direction is clear: materials with high embodied carbon will face cost penalties or compliance hurdles.

Why Spray Foam Is Vulnerable

Closed-cell spray foam insulation uses hydrofluorocarbon (HFC) blowing agents that have extremely high global warming potential. The embodied carbon of closed-cell spray foam is 5 to 10 times higher than fiberglass batts and 15 to 20 times higher than cellulose insulation for equivalent thermal performance.

Open-cell spray foam is better than closed-cell but still significantly higher than fiber-based alternatives.

Under embodied carbon scoring, specifying spray foam throughout a building's exterior walls could add enough carbon penalty to affect compliance or trigger offset requirements. The exact thresholds are being developed, but the risk is real for projects in the permitting pipeline.

What to Specify Instead

The alternatives are proven, cost-effective, and in many cases cheaper than spray foam.

Dense-pack cellulose. Excellent thermal performance, outstanding air sealing when properly installed, and one of the lowest embodied carbon values of any insulation material. Cellulose is made from recycled paper and actually stores carbon rather than emitting it.

Wood fiber insulation board. Used as continuous exterior insulation, wood fiber board provides thermal bridging reduction, moisture management, and carbon storage. It scores extremely well under embodied carbon metrics.

Mineral wool. Higher embodied carbon than cellulose but significantly lower than spray foam. Excellent fire resistance and sound attenuation. Works well as exterior continuous insulation.

Fiberglass batts with separate air barrier. The most cost-effective wall insulation when combined with a dedicated air barrier system (like airtight drywall approach or a membrane air barrier). R-21 batts with proper air sealing outperform R-38 spray foam on a cost-per-HERS-point basis on most multifamily projects.

The Timeline

Embodied carbon requirements are in active development at the state level. While the specific rules and timeline are not finalized, the regulatory direction is clear. Projects being designed now should consider the risk that these rules may be in effect by the time construction starts.

The smart move is to specify low-carbon materials now, before they are required. The materials perform well under current energy code, they cost the same or less than spray foam in most applications, and they position your project to comply with future requirements without redesign.