The Signal: News and Notes from the Pharos Team

Foam Board Insulations: Plagued By Ozone, Global Warming and Fire

Tom Lent May 20th, 2010 4 comments

Foam board insulation presents one of the tougher challenges for green building. With excellent performance characteristics and high R values - from 4 to 5 per inch or beyond - foam boards have been very popular for insulating foundations, walls and roofs in high performance designs. As we’ve reviewed the chemistry of these foams for the Pharos Project, however, we’ve learned that the chemistry that goes into making the most popular foams - polyisocyanate, such as Thermax, expanded polystyrene (EPS) such as Falcon Foam and extruded polystyrene (XPS) such as Styrofoam - is highly problematic for human health and the environment.

The manufacturing processes for both polyisocyanate and polystyrene are based upon highly toxic chemicals that receive red flags in Pharos as materials of very high concern. The toluene diisocyanate (TDI) building block for polyisocyanate is a known carcinogen and the styrene component of polystyrene is connected with a range of hazards from asthma to endocrine disruption, neurotoxicity and cancer. That, however, is just the beginning of the problems.

These plastics work their thermal magic thanks to the foaming process that creates countless tiny insulating pockets in the board. The CFC (chlorofluorocarbon) chemicals originally used to do this foaming were among the most potent ozone destroying chemicals. The Montreal Protocol, the international agreement to protect the earth’s ozone layer, has slowly forced the industry to phase out the worst ozone depleting agents and find alternatives. Some manufacturers are converting to HFCs (hydrofluorocarbons) while others are finally getting away from halogenated compounds entirely, converting to pentane-based foaming agents with little or no ozone destructive potential.

Avoiding damage to the ozone layer, however, has come at a cost. Some of these blowing agents, such as the HFC-134A used in Styrofoam are even more potent global warming gases than the CFCs they replaced, leading to serious questions about the basic efficacy of this insulation to fight global warming, an issue that warrants further attention. Furthermore, the hydrocarbon blowing agents being used instead of the HCFCs are adding to the flammability of these plastics. While manufacturers rarely disclose their fire retardant on a product’s Material Safety and Data Sheet (the MSDS), our research indicates that halogenated fire retardants are used in virtually all US production - usually TCPP (tris(chloropropyl) phosphate) in polyisocyanates and HBCD (hexabromocyclododecane) in the polystyrenes.

The HBCD fire retardant in polystyrenes is now the target of high concern globally. This persistent, bioaccumulative, and toxic chemical is associated with hormone disruption and reproductive disorders and is one of the top sixteen chemicals being studied for elimination on the European Commission’s “Substances of Very High Concern" list. According to the Green Science Policy Institute (GSP), “It has been widely detected in household dust, sewage sludge, breast milk and body fluids as well as wildlife and the global environment. HBCD is also used with fabrics and plastic; however 85% is used with polystyrene insulation, which is likely the primary source of the global contamination.”

The TCPP in polyisocyanates is not yet as well studied as HBCD, but indications are that it may not be any better. This neurotoxic chemical is a close relative of tris, the carcinogenic compound that was banned as a fire retardant in baby pajamas in the late 70s. 

So what is a green designer or builder to do?

* Speak up and push for disclosure - Let your foam insulation sales reps know that you don’t like the choices currently available on the market, and push them to disclose what they are using and explore alternatives. European firms are beginning to employ safer non-halogenated fire retardants like triethyl phosphate (TEP).

* Ask for versions without fire retardants for below grade - As Environmental Building News noted in an excellent article on the topic, a significant percentage of insulation applications are below grade and hence have zero fire risk and have no need for retardants. Ask your insulation reps to provide a well-marked retardant-free option for these applications.

* Avoid the toxic foam boards entirely - Use a blanket or batt insulation that does not require halogenated flame retardants where possible. Where a board insulation is needed, check out the fiberglass and mineral fiber-based boards. We’ll discuss the options for formaldehyde-free binders and bio-based fibers in these blankets and boards as well as aerogel technology in blogs in the near future.

Some very creative alternatives are on the horizon, including Ecovative Design’s board made from agricultural byproducts woven together by the mycelium roots of mushrooms. Sounds implausible, but they’ve already demonstrated a class 1 fire rating and passed a battery of ASTM tests for mold growth, water sorption, and vapor transmission. It’s only available as a packaging material this year, but we’ll be watching them and rooting for their success.


Bill, January 28th, 2011

Let us all install foam insulations on our homes. It will really help us a lot and not only us but also the mother earth. I hope this post really helps us protect our home and the earth as well.

Tom Lent, December 17th, 2010

The California Environmental Contaminant Biomonitoring Program (CECBP) Scientific Guidance Panel (SGP) undertook a thorough evaluation of the science on TCPP and concluded that "TCPP is structurally similar to three chemical compounds that have been identified as causing cancer. Tris(2-chloroethyl)phosphate and tris(2,3-dibromopropyl)phosphate are listed as known to cause cancer under Proposition 65, and tris(1,3-dichloropropyl)phosphate was identified as a probable human carcinogen, based on sufficient evidence in animals, by the U.S. Consumer Product Safety Commission." (from "Brominated and Chlorinated Organic Chemical Compounds Used As Flame Retardants, Additional Information on Four Flame Retardants" from the CECBP SGP

The Sailor, December 17th, 2010

In this article the author made various statements regarding the toxicological properties of HBCD and TCPP, both flame retardants which are used in plastic and foam board insulation. The statements on TCPP are incorrect and suggestive as none of the statements can be backed up by science. TCPP has been evaluated recently in the EU in a thorough risk assessment and more recent in the REACH registration, where the extensive dataset has been evaluated by external experts and EU authorities, including data on neurotoxicity and genotoxicity. The conclusion was that TCPP is not a neurotoxin nor a carcinogen, and is not an environmental pollutant. In addition, the substance should not be compared to TRIS, which is obviously not a “close relative” to TCPP when it comes down to the toxicological profile, based on comparison of all the data generated for both products.

Craig, June 2nd, 2010

This is a great start to the full disclosure of the potential dangers of the ubiquitous foam insulations. With a stated goal of 83% reduction in U.S. energy use by 2050 the feds have put the pressure on building professionals to enhance residential thermal performance. In Maine, where I reside, most of the housing stock was built before 1970 when oil as cheap and houses were designed to breath. Indoor air quality could not be more closely linked to our choices of materials we envelope ourselves in. Using less fuel oil and oil based materials is critical to the health of this planet but we must also pay even greater attention to the quality of indoor air as we "button up". Thanks for your great work.

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