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Spray Foam Insulation

Published July 16th, 2015 by Devteam

WHY USE SPRAY FOAM INSULATION?

Spray polyurethane foam (SPF) is better than any other type of insulation at reducing air leakage.

With foamed-in-place insulation, it is relatively easy (though not inexpensive) to fill wall and ceiling cavities completely. Closed-cell spray foam provides a higher R-value per inch (6.5) than less expensive insulation types like cellulose and fiberglass (3.5 to 3.7).

Most spray polyurethane foam is called “two-component” foam. Two ingredients—conventionally called “A” and “B” components—are mixed on site using special equipment mounted in a trailer or truck. Heated hoses convey the components to a mixing gun that sprays the chemicals on the surfaces to be insulated.

A chemical reaction begins as soon as the chemicals are mixed. The liquid mixture foams, expands, and eventually hardens.

WHAT TYPES OF SPRAY FOAM INSULATION ARE USED?

CLOSED CELL:

Two-pound foam, also known as closed-cell foam, has a density of about 2 lb. per cubic foot and an R-value of 6 to 6.5 per inch. Two-pound foam is significantly more expensive than half-pound foam.

Closed-cell foam is a vapor retarder. Two and a half inches of closed-cell foam have a permeance of 0.8 perm.

The blowing agents in most types of closed-cell spray polyurethane foam are hydrofluorocarbons (HFCs) with a high global warming potential. Because the global warming potential of these damaging blowing agents is 1,430 times more potent than carbon dioxide, many green builders avoid the use of closed-cell spray foam.

Closed-cell is more expensive and does not perform well in this zone.

OPEN-CELL:

Half-pound foam, also known as open-cell foam, has a density of about 0.5 lb. per cubic foot and an R-value of 3.5 or 3.6 per inch.

Open-cell foam is relatively vapor-permeable. Three inches of open-cell foam have a permeance of 16 perms.

Some of the low-density foams are made in part from bio-based raw materials — for example, soybean oils — in place of a portion of the petrochemicals. Open-cell foams use water or carbon dioxide as the blowing agent.

Compared with closed-cell polyurethane, open-cell products use significantly less material, making them attractive from a resource-use standpoint. However, open-cell foams have a lower R-value per inch than closed-cell foams.

Open-cell seals as well as closed and is more economical than Closed-cell and performs well in this zone. For this reason, Pyramid Homes uses open-cell spray foam insulation when building homes.


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