Spray polyurethane foam, or SPF, is a spray-applied insulating foam plastic that is installed as a liquid and then expands. Many manufacturers offer open-cell, low-density products as well as closed-cell, two-pound foams. For builders looking for the most cost-effective mix, a hybrid system of the foamed-in-place options may suit their needs.
The 2013 New American Home in Las Vegas did it right. The builder is using open-cell spray foam on the exterior walls and closed-cell for the roof. Josh Anderson, president of Element Building Co. told BUILDER: "On top of being an incredible water-proofer, it also adds R value to the roof. We're getting an effective R value on the roof in the high 40s or 50s."
As a vapor barrier, air barrier, and insulator, the open-cell insulation from Bayer Material Science that Anderson installed is well-suited for the demands of the Las Vegas climate.
One LinkedIn commenter offered this simple rule: "Where moisture is an issue, closed-cell it is" the solution.
Open-Cell Spray Foam
Closed-Cell Spray Foam
3.7 per inch
6 per inch
|Able to deflect water/|
reject bulk water
|Able to accommodate seasonal movement|
|Typical Blowing Agent|