Image Credit Lloyd Alter
It's getting harder and harder to know what to use in green building. Sprayed polyurethane foam is a favourite among green builders because of its high R value and tight seal, but the Environmental Protection Agency is raising some questions about its safety.
Tristan Roberts at BuildingGreen explains that the issue is "Isocyanates, such as MDI (methylene diphenyl diisocyanate), that are chemicals that react with polyols to form polyurethane."
It is evidently not a problem when it is cured, but more and more do-it-yourself types are using the stuff.
According to the EPA,
EPA is concerned about potential health effects that may result from exposures to the consumer or self-employed worker while using products containing uncured (unreacted) MDI and its related polyisocyanates (e.g., spray-applied foam sealants, adhesives, and coatings) or incidental exposures to the general population while such products are used in or around buildings including homes or schools.
Tristan Roberts writes:
As Steve Owens, assistant administrator for EPA's Office of Chemical Safety and Pollution Prevention, put it, "There has been an increase in recent years in promoting the use of foams and sealants by do-it-yourself energy-conscious homeowners, and many people may now be unknowingly exposed to risks from these chemicals." You can add to that a growing number of complaints about adverse health effects from homeowners and occupants of office buildings where SPF has been applied during energy retrofits.
Tristan reports that builders " have tended toward defense of SPF and annoyance (that's putting it politely) at EPA. The undercurrent seems to be: Is the whole industry going to get stained because of some untrained DIYers?" Polyurethane foam has really high R-Values and seals really tightly to studs, solving air leakage and insulation in one application, and many green builders love the stuff. But Robert Riversong writes in his thoughtful comment:
There is a large and growing number of anecdotal complaints about the health impacts of field-applied SFP foam, particularly low density or "open cell" proprietary urethane foams. These are without exception professionally-installed spray urethane foam insulations, not DIY projects.... In far too many instances, the home-owners have had to permanently vacate their new or newly-renovated homes because of chemical sensitivity apparently initiated by the insulation. As we know from other chemical sensitizers, such as formaldehyde, initial exposure causes increased and sometimes debilitating reactions to a wide variety of chemical substances.
I am often concerned that in America, green means energy efficient and health doesn't matter much; otherwise heat recovery ventilators would be mandatory in every new home, like they are in Canada, to ensure that tightly sealed, energy efficient homes get some fresh air. So a lot of green builders think we are nuts to talk about the dangers of fire retardants in stryrofoam or outgassing from polyurethane.
But the tighter we seal our houses, the more we should be worrying about the toxicity of what we put into them.