Spray foam and fire protection
Hello, I have been asking various people about the following and am getting many different opinions. I understand that sprayed in place foam needs to be covered with a building material to provide a fire retarder, usually approx 15 minutes.
My question is, “is there any type of sprayed on foam insulation that will not ignite when exposed to an open flame?” I did watch a television program that showed a sprayed foam installed to the ceiling area between the floor joists in a basement. They held a torch to the material and it did not burn. Does this material need to be covered if it is installed in a area that people live?
Thanks for any input. Dave.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
David,
If it gets hot enough, any foam will burn.
There is at least one brand of spray foam that can be installed in a crawl space, basement, or attic without a covering of gypsum wallboard as fire protection. The foam is called Staycell One Step 255, and it is manufactured by a company called Preferred Solutions.
This type of foam cannot be used uncovered in the main living area of the house. Moreover, some building inspectors may not accept the use of the foam without drywall protection. You can read more about the product here: New Green Building Products.
In some instances you'll be allowed to use an intumescent paint on sprayed foam, which will stand up to direct flame for some period of time, even after the polyurethane is well above it's flashover ignition temp.
Not all foams are alike, from a fire hazard point of view. Polyurethane (and it's cousin polyisocyanurate) will not melt- it will char in place even when fully engulfed and burning on it's own. This makes it in some ways safer than polystyrene (XPS, EPS), which will melt, streaming burning gobs of liquid away as it burns, making ignition & thermal barriers even more important when rigid EPS or XPS is used than when polyiso or polyurethane are the foam in question.
But used properly & judiciously, they're all good.
In applications where fire resistance is at a premium, nothing quite matches the performance of rock wool though.