Great Stuff foam: very useful for gaps — but better solutions for fireblocking
bvillebound
| Posted in Energy, Heating & Insulation on
Hello all!
We are wrapping up the deep remodel of a beach house built in 1950 — which required up-to-Code upgrades for insulation, air sealing, fireblocking, etc, etc.
I discovered some interesting facts about Great Stuff foam during the process. Here is a quick recap. I hope this helps with your project:
- Great Stuff is the perfect solution for sealing the seams in foam board, and filling holes cut for pipes, electric cables, etc.
- Great Stuff is ideal for sealing exterior surfaces and holes, e.g. windows, doors and panels of foam board. It will not degrade like water-based foams.
- Great Stuff is closed cell polyurethane foam, so the insulation properties are similar to foam board.
- Great Stuff is also very flammable, like all polyurethane foam products. The cured foam will ignite at just 240 degrees F, significantly less than the ignition temperature of wood. In other words, Great Stuff will begin to burn before your wood studs. DO NOT install uncovered Great Stuff near any sources of flame or hot surfaces, e.g. furnaces, fireplaces, enclosed light fixtures, etc.
- You can significantly increase the yield from every can by spritzing the surface (and the foam) with water from a hand-held spray bottle. This will not affect adhesion on the surface. (Another big Thank You to FHB for this great article! It works!)
- DOW offers a “Fireblock” version of Great Stuff, which looks like another convenient solution. Many builders and electricians are switching to Great Stuff Fireblock, instead of the fireblock sealant used in commercial buildings. I thought this version of Great Stuff included fire retardants that made it non-flammable. I was surprised to discover that it also ignites at 240 degrees F! Yes, a “fireblock” product that will ignite BEFORE your wood studs! Curiously, this key fact is not included in the MSDS that I downloaded from the DOW website. We switched to the non-flammable fireblock sealants sold by Home Depot and Lowes, e.g. 3M and DAP.
I hope this is helpful!
Mark
Replies
So what is it you're selling anyway, or is someone simply paying you to slam Great Stuff?
Just want to help other FH members avoid this problem
Dear Dan:
As I noted in this post and a number of others, Great Stuff foam is an excellent solution for sealing windows, doors, foam insulation panels, etc. We used boxes of it on a recent 'deep remodel' project. The 'windows' version remains flexible, which is ideal for windows, doors and 'cut-and-cobble' installations of foam board in walls.
The problem is the very flammable 'firestop' version of Great Stuff -- and DOW is not alone; Hilti, 3M and a number of other manufacturers make similar foam based 'firestop' products.
I have no connection to any manufacturer in the industry, except as a customer. I simply hope that this information will help other tradespeople and customers avoid the problems we encountered.
Mark