News Brief

California Approves Flame-Retardant-Free Insulation Below Grade

Though products are not yet on the market, a state commission has given the go-ahead for select foam insulation without flame retardants or fire testing.


That’s how plastic foam insulation will have to be marked following a decision by the State of California Building Standards Commission to allow flame-retardant-free products to be used below grade. The boards will also have to say, in ½-inch-high red lettering, “This product is required to be installed below a minimum 3.5-inch-thick concrete slab on grade,” among other text explaining how the insulation must be used. Packaging will also instruct jobsite workers about storage requirements for the insulation, which will contain no flame retardants and have no fire-testing requirements.

That’s if this type of insulation ever makes it to the market, which is not guaranteed (manufacturers will need to see demand for the product and be willing to take the potential legal risk). But health advocates are claiming a “huge victory,” with an email from the Green Science Policy Institute (GSPI) declaring that flame retardants have “no fire safety benefit” and stating that the institute “applauds this very positive first step.”

The push for this type of ruling started bigger, with GSPI and others arguing to the International Code Council that flame retardants should not be needed in insulation that’s installed behind gypsum wallboard or underneath a concrete slab. A 2012 petition to change the rules in the International Residential Code was voted down, but work has continued at the state level, resulting in this first code ruling of its kind.

More on flame retardants in insulation

Getting Flame Retardants Out of Foam Insulation

New Flame Retardant for Polystyrene: Too Much Like the Old?

Increase Fire Safety Without Flame Retardants, Group Urges

For more information:

Green Science Policy Institute


Published March 4, 2019

Melton, P. (2019, March 4). California Approves Flame-Retardant-Free Insulation Below Grade. Retrieved from

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March 19, 2019 - 6:36 pm

Manufacturers have traditionally sold a separate below grade polystyrene insulation product.  It was sometimes a different color and had ribs on one face to drain water away from the slab or foundation wall. It seems like an easy fix to remove the flame retardants from an already existing product.  Secondly, under slab polystyrene insulation has other applications where fire retardancy is irrelevant.  Structural engineers often use it for void forms in places like open-air parking garage ramps, where its only purpose is to support a slab until the concrete cures.  Civil engineers sometimes use it to create a temporary pour joint between concrete slabs in road and bridge work - another application where fire retardancy is irrelevant.  

Taking an unnecessary toxic chemical out of foam insulation seems like a no-brainer.  I hope there are some insulation manufacturers willing to step up to the plate and oppose the fear-mongering by the chemical industry.  The designers and specifiers of green buildings will welcome the opportunity to specify below grade foam insulation without flame retardants. 

March 21, 2019 - 11:25 am

GSPI is going to propose a version of this to the ICC again this year. If that goes through for all of North America, I suspect manufacturers will be more interested in producing the special foam.