A step in the right direction, considering that flame retardants don't actually do that much.
A few years ago I was invited to visit the site of a new school being built out of Cross-Laminated Timber on a media tour day, when usually they pick up the garbage and tidy up the joint. It was perhaps the messiest firetrap of a site I had ever been on and I thought at the time, "Now I know why they put flame retardants in foam insulation."
It turns out I wasn't far off the mark; Paula Melton writes in BuildingGreen that, as of January 2020, California will allow flame retardant-free insulation below grade. It's the one place I never really worried about flame retardants; they aren't likely to get into the home, and as builder Michael Anschel once noted, "The poor worms, what will endocrine disruptors do to them?"But according to Paula Melton who spoke with Robert Agnew, who wrote the California study on its safety, there was still a concern.
The biggest concern from the work group, though—and from Agnew as well—was what might happen on the jobsite with untreated foam.
But as the chief of code development noted, “It’s not the worst thing that would be commonly found on a construction site.” Indeed, at that site where I saw the foam, they were storing jerry cans of gasoline right under the building too.
In the end, another expert tells Melton that all unprotected foam is dangerous, whether it has flame retardants or not.
One thing that we should be very clear about is that foam insulation is flammable, whether is has flame retardants in it or not,” he [Joe Charbonnet] told BuildingGreen. Flame retardants, he said, give “a false sense of security. All foam needs to be treated as a flammable material.” He said when any foam is installed under concrete or behind gypsum wallboard, that configuration “is much more effective at protecting lives from fire death than any chemical.”
Many insulations no longer have the really bad HBCD flame retardants that we have been complaining about forever; last year Dow and other manufacturers switched to polymeric flame retardants that are a “butadiene styrene brominated copolymer” that supposedly doesn't bio-accumulate. But according to Brent Ehrlich at Building Green, that still doesn't give it a totally clean bill of health.
This polymeric flame retardant is not benign, however. It is still a brominated compound that is persistent in the environment. Its long-term life-cycle impacts are unknown, and that has chemist Arlene Blum at the Green Science Policy Institute, and others, raising red flags.
So the option of using foam without a flame retardant at all underground is a welcome option. Think of the worms.