Spray Foam Insulation In Vented Attic

Installed in vented attics conditioned air is lost to the exterior.

Spray foam insulation in vented attic.

And because vented attics are subject to extreme high and low temperatures additional energy march 2007 i jlc i 2 insulating unvented attics with spray foam figure 1 spray foam is a good choice for roofs that are difficult to vent like a turret with converging rafters. Thanks to its air sealing properties foam insulation for vented attics particularly in cold and dry climates helps curb a stack effect where heated air escapes through the ceiling and eventually the attic and is replaced in lower levels of the home by drawn in outdoor air. An open cell foam low density spray polyurethane is a spray applied to provide continuous insulation and an air sealing barrier. There is no need to install any spray foam on your attic floor since you will be moving your air barrier and your insulation layer to the sloped roof assembly.

If the atmospheric combustion appliances start off in a vented attic the building code doesn t require those vents because the appliances are already connected to the outside and should get plenty of air. The two products most often used in an unvented attic assembly are medium and low density sprayed polyurethane foam spf. In typical construction and climates building code tables can be followed when using spf as an insulation and air seal. The most important reason to transform your vented unconditioned attic into an unvented conditioned attic is to bring your air handler and ductwork inside your home s conditioned space.

However in a traditionally insulated attic insulation on the ceiling the attic is vented. When we seal the attic with spray foam it s as tight as a butter tub. There are numerous ways in which an unvented attic insulated with spray foam can reduce a home s energy consumption. This spray foam is applied as a low or high pressure two component polyurethane spray foam that can be applied onto walls in unvented attics to ducts and ceilings and in vented attics and crawl spaces.

One huge benefit of the spray foam insulated attic is that conditioned air leakage from the ac furnace duct system is contained and used to condition the attic. This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4. Foam insulation for vented attics placed on the attic floor can also work to minimize moist warm indoor air from entering the attic and causing potential roof damage from condensation on the roof deck in. The insulation reduces wildly high temperature spikes and so the attic becomes a conditioned part of the home like any other room.

When spray foam is installed on the underside of the roof deck the attic space is insulated from heat that otherwise would be entering the attic. Whether the home is old or new however anyone considering spray foam insulation would be wise to ask this question.