Attic Closed Cell Foam Underlayment

The underlayment is a vapor barrier called rooftop guard.

Attic closed cell foam underlayment.

Many builders in cold climates use closed cell spray foam instead because of its lower water vapor permeability which means it doesn t need the extra step of installing a vapor retarder. Closed cell foam can be over three times that with a density of 1 75 pounds per cubic foot or more. Open cell spray polyurethane foam or closed cell spray polyurethane foam ccspf insulation can be sprayed along the underside of the roof sheathing to provide a conditioned and insulated attic space that can be durable and efficient in. It also stops air flow through and.

But foam also traps moisture in the roof in case of a leak. Control rain in any roof assembly an underlayment e g. Closed cell foam has a higher r value than open cell foam usually about 6 0 per inch. But open cell spray foam with a vapor retarder can work too.

Closed cell foam can also increase the racking strength of attic walls which is the ability of a structure such as a wall to withstand horizontal forces. But some closed cell foams like tiger foam s e84 closed. A foams r value is its resistance to heat flow or in other words how well they insulate. Unvented roofs with spray foam applied to the underside of the roof deck have been used since the mid 1990s.

Closed cell medium density spray polyurethane foam ccspf insulation can be used to create an unvented roof assembly for any climate zone. In general most closed cell foam and many open cell foam products can be installed without the need of an intumescent coating in an unvented attic and therefore can go bare provided a drywall ceiling 15 minute thermal barrier directly below the attic exists. Closed cell spray foam works in all climates but especially well in climate zones 5 through 8 where high r values are desired and where air impermeable insulation also must be a vapor retarder. Low density open cell foam is permissible but in climate zones 5 and above it has to be covered with a vapor retarder coating like rigid foam or.

A sealed and insulated roof deck can t dry inward to the attic if the roofing happens to let water.