Healthier Insulation

Why are flame retardants in building insulation?

All foam plastic insulation sold in the U.S.--polystyrene (XPS and EPS), polyurethane, and polyisocyanurate--contain flame retardants to meet building codes. This is one of the leading uses of flame retardants, most of which are harmful to health and do not provide a fire safety benefit.

Since energy efficiency is important to reduce climate change, the use of foam plastic insulation is increasing. Unless flammability standards change, flame retardant use in insulation products will continue to grow similarly. Building codes for many uses of foam plastic insulation should be updated to allow the choice of flame retardant-free foam.

Do flame retardants in foam plastic insulation make us safer?

No independent studies have demonstrated a fire safety benefit from flame retardants in foam plastic insulation. The Steiner Tunnel test--currently used to measure the flammability of insulation--does not accurately measure the fire risk of materials which melt and drip like foam plastics.

Further, flame retardant chemicals do not increase fire safety when used beneath a foundation or behind thermal barriers. Building codes already require that insulation be protected by a thermal barrier, such as gypsum wallboard, capable of withstanding 15 minutes of flashover fire.

Building codes in Sweden, Norway, Finland, and Spain allow flame retardant-free insulation behind barriers. Consequently, the market in Scandinavia is dominated by polystyrene boards without flame retardants. A UN Risk Management Evaluation stated, "By using thermal barriers it is possible to fulfill fire safety requirements in most uses in construction and buildings with EPS and XPS without a fire retardant.” The evaluation added that flame retardant-free EPS and XPS insulation “do not represent a higher cost to the manufacturer." Fire losses in these countries have not increased in the years since this code reform.

Learn more about the harms and lack of fire safety benefit from flame retardants in building insulation here. 

What are healthy building insulation options?

Alternative insulation materials with preferable toxicological or environmental profiles are available. Natural wool, cellular glass, cork, phenolic thermosets, and cementitious foam can meet flammability standards without the addition of harmful flame retardant chemicals. Some of these materials are cost-competitive when compared by insulation performance.

What has the Institute done?

We work with architects, builders, policymakers, and fire safety experts to update building codes so that builders have the choice to avoid flame retardants in insulation when they do not improve fire safety.

In 2013, we supported California Assembly Bill 127 (AB 127), which directs the State Fire Marshal to reexamine flammability standards for building insulation, and to allow flame retardant-free building insulation while maintaining fire safety.

In 2019, the California Building Standards Commission approved our proposal and voted unanimously to update the state’s building codes to allow below-grade use of foam plastic building insulation without flame retardants.

Now California builders and architects can begin to specify flame retardant-free insulation for use below the concrete foundations of buildings and residences. The next steps are similar changes in the international model code and behind all thermal barriers.

We also have conducted research and published peer-reviewed journal articles on flame retardants in insulation (see resources below).