In Summary:
Spray Foam products marketed as being healthier may be formulated without some of the hazardous chemicals traditionally found in SPF products, but don’t replace the really bad actor chemicals.
  • SPF insulation - even those with improved formulations - remain at the bottom of our Stoplight chart, in dark red.

In Detail:
It’s a familiar scenario: Healthy Building Network will present the HomeFree stoplight chart on insulation, which lists SPF at the bottom in dark red.  Someone - usually a contractor - will raise their hand and offer something along the lines of,
“SPF works so well, and is so easy to install… what if we use the ‘green’ kind?”

Good question. SPF products marketed as being “green,” or “natural,” or otherwise improved are beginning to hit the market.  Project teams may be tempted to use these products.

But our review of these products confirms that, while these products are free of some of the traditional bad actor chemicals found in SPF foams, they still contain hazardous substances, and should be avoided whenever possible.

Here’s why. (Warning! Science ahead!)

The hazards from SPF come from two issues: 1) the fundamental limitations of polyurethane chemistry; and 2) additives that provide various performance characteristics.

Polyurethanes are made by reacting two types of substances - a polyol and an isocyanate.  Exactly which polyol and which isocyanate can be variable, depending on the type of end product desired.  

Some polyols based on soy or other plant derivatives are available for use in polyurethane products.[1]  While this is an important shift in the market, when used in SPF these polyols represent only a portion (we’ve see up to around 20%) of the finished foam.[2]  

Typically, half or more of an SPF product is comprised of isocyanates.[3] These substances are extremely potent asthmagens - as little as one drop could be enough to cause someone to develop asthma.[4]  These isocyanates continue to react after the SPF has hardened (there’s no agreement in the industry about exactly how long it takes to fully cure),[5] and building occupants can be exposed.

The other half is a mixture of polyols and other chemicals. An expert recently testified that he draws from a list of 200 chemicals in developing mixtures for his SPF clients.[6] Manufacturers don’t typically disclose many of them.
There are two general types of SPF, open cell and closed cell. Open cell SPF includes water as a blowing agent. But almost all closed cell SPF contains halogenated blowing agents, and these are problematic. For many years, closed cell SPF formulations have relied upon a class of blowing agents called hydrofluorocarbons (HFCs), which are potent greenhouse gases. The industry is shifting to a new class of blowing agents called hydrofluoroolefins (HFOs). They are not potent greenhouse gases, but create another atmospheric problem. They use a chemical called carbon tetrachloride in their production. Carbon tetrachloride is a powerful ozone depleting chemical that is not regulated if it is a feedstock for producing other chemicals.  We are already seeing increases in emissions of CTC into the atmosphere as HFOs become more widely used.[7]

In addition to these problematic blowing agents, SPF includes a variety of other harmful chemicals like amines (which may contribute to respiratory effects [8]), and chlorinated flame retardants, which have been the focus of global attention recently for their ability to impact both human health and wildlife.[9]

For more information on the composition of SPF, see its Common Product Profile.

Note: Originally published in Feb, this blog was updated April 4, 2017 to reflect new findings about the linkages between the blowing agents used in SPF and ozone depleting chemicals.


[1] See for example, BioBased Technologies. “Agrol 2.0 - 4.0 Technical Data,” September 2016.

[2] See for example, “Agribalance.” Demilec Inc. Accessed March 15, 2017.

[3] See for example, Demilec. “A-PMDI Safety Data Sheet,” March 11, 2015. which is mixed in a 1:1 ratio parts A and B.

[4] Parrish, Meagan. “$90B Whistleblower Suit Targets World’s Biggest Chemical Companies.” Chem.Info, September 19, 2016.

[5] US Environmental Protection Agency. “Vacate and Safe Re-Entry Time for Spray Polyurethane Foam Application.” Overviews and Factsheets. Accessed March 7, 2017.

[6] Testimony of George Thompson in Beyer, et al, Plaintiffs -versus- Anchor Insulation Co., Inc., Defendant, Case No. 3:13-CV-01576 (United States District Court, District of Connecticut), March 13, 2017.

[7] Honeywell is producing HFO-1234ze at a chemical plant in Louisiana. This blowing agent is used in SPF. Carbon tetrachloride releases soared after the plant began producing HFO-1234ze in 2015.

[8] “Staff Review of Five Amine Catalysts in Spray Polyurethane Foam.” Status Report. United States Consumer Product Safety Commission, September 19, 2012.

[9] DiGangi, Joseph, Arlene Blum, Åke Bergman, Cynthia A. de Wit, Donald Lucas, David Mortimer, Arnold Schecter, Martin Scheringer, Susan D. Shaw, and Thomas F. Webster. “San Antonio Statement on Brominated and Chlorinated Flame Retardants.” Environmental Health Perspectives 118, no. 12 (December 2010): A516–18. doi:10.1289/ehp.1003089.