How Much Closed Cell Spray Foam do I Need? New York NY

The thickness of spray foam really depends on where it’s being applied and what you’re trying to accomplish.

Now generically speaking, we usually recommend open cell spray foam to be 6- to 10-inches on a roof deck or ceiling and 3-inches in the walls. Closed cell spray foam should be 4- to 5- inches on the ceiling and 2- to 3-inches in the walls.

This might come as a surprise to you, but honestly, this is all the spray foam it takes to get the biggest bang for your buck with the air seal and thermal resistance needed for certain areas of the home. We have had homeowners in the past request 8 – to 10 -inches of closed cell on their roof deck.

The idea is that the more foam, the higher the R-Value, but that’s not how that works either. R-Value does matter, however thermal resistance is what R-Value measures. If you have an air seal, that’s the most important thing. Stacking R-Value on top of R-Value diminishes your return and you’re just wasting money.

After you reach a certain threshold, like the amount required to create an air seal, you don’t see anymore return on investment by adding the extra foam.

The measurements we use come directly from the manufacturer and those measurements create not only an air seal but also thermal resistance.

At the end of the day, a good contractor doesn’t want to see a homeowner wasting money. The whole point with creating an air seal is to create a more comfortable and energy-efficient home that will save money in the long run.