Healthier Insulation


Problem: For improved energy efficiency, foam plastic building insulation (polystyrene, polyisocyanurate, and polyurethane) is increasingly used in “green” buildings.

To meet flammability standards, the manufacturers often add flame retardant chemicals that are either known to be toxic or lack adequate health and environmental information. These chemicals do not increase fire safety when used below-grade or behind thermal barriers. (Navigate to Research to learn more.)

We have been working with architects, builders, policymakers and fire safety experts to reduce the use of flame retardants in building materials when they do not improve fire safety.

Foam plastic building insulation is used:

  • in wall and ceiling cavities, including attic insulation (spray foam or foam board)
  • below-grade foundation (foam board)
  • under concrete slabs (foam board)




Flame retardant chemicals in building insulation


In recent decades, the brominated flame retardant HBCD was added to polystyrene insulation (EPS and XPS). It bioaccumulates in fat, becoming more concentrated as it moves up the food chain. Marine mammals have on average 100 times greater levels of HBCD in their bodies than small aquatic organisms.

HBCD is associated with adverse reproductive, developmental, and neurological health effects. This harmful flame retardant was banned from use by the Stockholm Convention, a global treaty adopted by over 180 countries in order to reduce the release of Persistent Organic Pollutants (POPs).

PolyFR – brominated styrene butadiene copolymer

As manufacturers phased out HBCD, they substituted PolyFR, a polymeric brominated flame retardant. Adequate data on PolyFR is not currently available; according to the EPA,  it is very persistent in the environment. PolyFR also presents serious lifecycle concerns, as research shows it breaks down into smaller and likely more toxic molecules. Like other brominated flame retardants, it may produce potentially carcinogenic compounds during combustion.

TCPP – (Tris(1-chloro-2-propyl) phosphate)

The chlorinated flame retardant TCPP, is used in most polyurethane and polyisocyanurate insulation (spray foam insulation). Research shows TCPP can accumulate in the livers and kidneys of rats, may be neurotoxic, and may cause reproductive toxicity in female mice.

HBCD bioaccumulates up the foodchain. (Covaci, 2006)





HBCD and TCPP are global pollutants found in:

  • the environment and animals
  • soil, sediment, and sewage sludge
  • indoor air and dust
  • and breast milk

Facts: Flame retardant chemicals in building insulation

Flame Retardant Name and ID#Use in insulationChemical ClassHealth and Environmental ConcernsLegal restrictions




Expanded and extruded (EPS and XPS) foam board insulation

Brominated organohalogen flame retardant

Neurodevelopmental toxicity

Strong potential to bioaccumulate

Persistent in air and subject to long-range transport

Very toxic to aquatic organisms

Banned by the European Union in 2015

Recommended for global elimination by the Stockholm Convention

Phased out by Canada in 2016


Tris (1-chloro-2-propyl) phosphate


Polyurethane and polyisocyanurate insulation (foam spray and boards)

Chlorinated organophosphate flame retardant

Persistent in the environment

Accumulates in livers and kidneys

Potential carcinogen, endocrine disruptor, reproductive toxin, and neurotoxin

Lack of data

European Union: Regulated in toys under Toy Safety Directive

Under study at the U.S. Environmental Protection Agency and National Toxicology Program

Listed on the California Safer Consumer Products Candidate List

Poly FR

Brominated styrene butadiene copolymer

CAS RN: 1195978-93-8

Expanded and extruded (EPS and XPS) foam board insulation

Brominated organohalogen flame retardant

Persistent in the environment

Lack of data


In 2013, California passed Assembly Bill 127 (AB127), directing the State Fire Marshal to reexamine flammability standards for building insulation, and if appropriate, to propose changes to the building and fire codes allowing for certain applications of foam plastic building insulation without the addition of chemical flame retardants, while still maintaining overall building fire safety.

Research makes the case for updating building codes

Flammability study finds adding flame retardants to below-grade foam plastic insulation provides no added fire safety benefit

The California Office of the State Fire Marshal (OSFM) directed researchers at Oklahoma State University to study foam plastic building insulation installed below-grade with and without added flame retardants.

The study found that:

  • Adding flame retardants to foam plastic insulation does not significantly change peak heat release rates.
  • The time to ignition for foam plastic insulation without flame retardants is comparable to other combustible construction materials.
  • When installed below grade, insulation without flame retardants has no risk of fire spread to the structure and will not endanger occupants or responders.
  • California’s residential building codes can be safely updated to allow use of below-grade foam plastic insulation without added flame retardants.

Read the full report, published on the California Office of the State Fire Marshal’s website.

Peer-reviewed paper: A case for re-evaluating building codes

Our interdisciplinary peer-reviewed paper, Flame retardants in building insulation: a case for re-evaluating building codes, explores the history, fire safety, health and environmental issues of flame retardants in building insulation. After extensive review of fire science studies, we concluded that flame retardants in building insulation do not provide a fire safety benefit for many applications.

We found that:

  • Since 1961, building codes have required foam plastic insulation materials to meet flame spread requirements as measured by the Steiner Tunnel test. 
  • The Steiner Tunnel test does not accurately measure the flame spread of foam plastics.
  • Flame retardants are added to foam plastic materials to pass the Steiner Tunnel test, but they do not provide fire safety benefits in many building applications.
  • Fire safety for foam plastics is provided instead by code provisions requiring firestopping and thermal barriers.

Read the full study, published in Building Research & Information
Read more on our blog


Picture shows the Steiner Tunnel test, which does not accurately measure the flame spread of materials which melt and drip like foam plastics. Photo: Intertek Testing Services, Inc.

Code Change

For healthier and energy-efficient buildings, codes and standards need to be updated to reduce the use of harmful flame retardant chemicals while maintaining fire safety.

In 2018, the California Office of the State Fire Marshal (OSFM) submitted a proposal to allow below-grade polystyrene insulation without added chemical flame retardants.

This proposal was based on research conducted by internationally-recognized fire science experts at Oklahoma State University (see above) and supported by a diverse group of stakeholders. On January 16, 2019 the  California Building Standards Commission voted unanimously to update the state’s building codes to allow below-grade use of foam plastic building insulation without flame retardants. As a result of this decision, California builders and architects will now be free to choose flame retardant-free insulation for use below the concrete foundations of buildings and residences.
A similar code change proposal has been submitted by the fire science engineering firm Reax Engineering to the International Code Council in for consideration at their May meeting in Albuquerque.

To learn more about this proposal and below-grade polystyrene insulation without added flame retardants, please refer to either:



Architects and Builders

Press: Healthier Insulation

SF Chronicle: Law may cut use of flame retardants in buildings

Gov. Jerry Brown has signed a law that may lead to a change in state building standards that would discourage the use of potentially hazardous flame-…

08 Oct 2013

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KQED Science: An environmental catch-22: fire safety chemicals in in…

Last year, Gov. Jerry Brown directed state agencies to reduce water use and greenhouse gas emissions through a green building action plan to “shrink the st…

26 Jun 2013

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CBS5 ConsumerWatch: East bay lawmaker wants toxics out of insulation

Assemblywoman Nancy Skinner of Berkeley is calling for a change in the state’s building code that would lessen the need for toxic chemicals in insulation. Julie Watts repo…

27 May 2013

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SFGate: S.F. ex-firefighter now battles cancer

Tony Stefani used to be a firefighter and a cancer patient. The two, he believes, had something to do with each other. Stefani was a firefighter i…

05 Feb 2013

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SFGate: Flame retardants may leach from your walls

Couches throughout the nation have become notorious for containing flame-retardant chemicals that may do more harm than good. Now, it turns out, t…

04 Feb 2013

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KQED Science: Flame retardants, redux: from toxic couches to buildin…

Speaking before a roomful of breast cancer researchers and activists in San Francisco earlier this month, Arlene Blum revealed her latest pla…

28 Nov 2012

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Scientific American blog: The environmental fallout of greener build…

Newer homes are remarkably energy tight thanks to superior insulating materials that are in wide circulation today. The energy savings can be substa…

28 Nov 2012

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Science Daily: Health and environmental risk in flame retardants in …

From Science Daily Researchers in the United States are calling for a change to the US building codes, following a study showing that the mandatory flame retardants r…

25 Nov 2012

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Washington Post: Concern grows over use of flame retardant HBCD

From the Washington Post Hexabromocyclododecane, commonly known as HBCD, is a flame retardant that is starting to give a lot of green builders headach…

04 Mar 2011

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Science & Policy Blog: Healthier Insulation

HBCD is on the way out – but use of questionable alternatives will p…

This week, the United States celebrates Thanksgiving. But internationally, countries that have signed the Stockholm Convention on Persistent Organic Pollutants have a dif…

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A new year, with promising new regulations

2013 was a productive year for fire safety and for environmental health! Two important regulatory changes that take effect this year have the power to reduce the use …

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USGBC honors leaders, unveils new building health initiative

The US Green Building Council Northern California Chapter’s annual Super Hero Awards gala, held last Tuesday in San Francisco, honored leaders in the nonprofit, education…

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HBCD alternatives assessment: narrow focus misses large problems

Polymeric flame retardant evaluated as HBCD alternative in Environmental Protection Agency’s Design for the Environment (EPA DfE) assessment presents unknown risks and po…

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World sees the light and bans HBCD. US stays in the dark.

In a historic decision, over 100 governments from around the world have agreed to list HBCD (hexabromocyclododecane) for global elimination. This ban means you can’t prod…

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New study: health and environmental risk in building insulation

Foam plastic insulation materials such as polystyrene, polyurethane, and polyisocyanurate are important to increase the energy efficiency of buildings and reduce carbon f…

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Presentations: Healthier Insulation

Fire Safe and Healthy Building Insulation

Speaker: Joe Charbonnet, Ph.D. Staff Scientist Event ICC Local Chapter Meetings Date October 15, 2019 Location Be…

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Sewers to Slabs: Radically Reimagining a Less Toxic World

Speaker: Joe Charbonnet, Ph.D. Staff Scientist Event Sewers to Slabs: Radically Reimagining a Less Toxic World Date Ju…

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Flame Retardants in Recycled E-waste: Implications for the Circular …

Speaker: Joe Charbonnet, Ph.D. Staff Scientist Event Webinar: The Future of Electronics in the Circular Economy Date J…

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How To Limit Flame Retardant Use: The Class Concept Or Code Reform?

Speaker: Joe Charbonnet, Ph.D. Staff Scientist Event 9th International Symposium on Flame Retardants (BFR) Date May 17…

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Improved Building Codes For Fire Safety and Health

Speakers: Arlene Blum, Ph.D. Executive Director Joe Charbonnet, Ph.D. Staff Scientist Event Safer Insulation Dinner …

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Improved Flammability Standards for Fire Safety and Health

Speakers: Arlene Blum, Ph.D. Executive Director Event Flame Retardants in Furniture and Building Insulation Date Apr…

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Flame Retardants in Furniture & Building Insulation Foams: Policies …

Speaker: Avery Lindeman Green Science Policy Institute, U.S. Event DIOXIN 2016 Date Sunday, August 28 - Friday, Septemb…

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Inventing Green Chemistry Alternatives to the “Six Classes” of Harmf…

Speaker: John Warner, PhD President, Warner Babcock Institute for Green Chemistry Event The Flame Retardant Dilemma and Beyo…

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Healthier Materials = Healthier Lives, the Next Chapter of Affordabl…

Speaker: Gina Ciganik Advisor of Housing Innovation at Healthy Building Network Event The Flame Retardant Dilemma and Beyond…

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A History of Thermal Insulation Regulations in California

Speaker: Justin Paddock, JD Chief, California Bureau of Electronic and Appliance Repair, Home Furnishings and Thermal Insulation (BEARHFTI) [toggle header="More about …

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What designers need: A restorative material economy

Speaker: Robin Guenther, Principal, Perkins + Will Event BIFMA Healthy Furniture Workshop: An Investigation into Stain-Repell…

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Chemical Management Policy Issues in China: Social and Economic Anal…

Speaker: Jianguo Liu, Ph.D., College of Environmental Sciences & Engineering, Peking University, Beijing, P. R. China Event S…

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