Open Or Closed Cell Foam For Attic

While the denser closed cell variety does not readily absorb moisture open cell foam can draw it in like a sponge.

Open or closed cell foam for attic.

Using spray foam insulation in an unvented attic application. Closed cell foam can be over three times that with a density of 1 75 pounds per cubic foot or more. Most open cell foam has a density of about 5 pounds per cubic foot. Open cell foam weighs 1 2 pound per cubic foot and closed cell weighs 2 lbs per cubic foot.

There is 300 difference there but the cost they give you is about a third difference and open cell foam at 12 inches will not give you the performance of 2 inches of closed. Open cell spray foam is a perfectly acceptable insulation product to use in attics. If you do not use the attic for a habitable purpose you might want to keep your thermal barrier on the floor of the attic. Closed cell foam can also increase the racking strength of attic walls which.

Open cell should be at least 6 inches in depth and closed cell 4 inches or more of each depending on local code. Light density open cell spray foam insulation and medium density closed cell spray foam insulation. Do it right and your roof will not rot. A foams r value is its resistance to heat flow or in other words how well they insulate.

Others like david butler see his comment below say you need to do it only if a moisture problem develops. This type of spray polyurethane foam can be classified into two different types. Closed cell foam is much denser than open cell foam. There you have it.

The myth that open cell is more economical is bullshit. These two types of spray foam insulation both contain polyurethane that can be potentially dangerous to the environment and to health upon exposure. I have open cell in my house since 2004 and i would not use it in a dogs out house. Lstiburek says to do it for every spray foam attic.