Vented Attic With Spray Foam

An unvented attic system relies on an air seal and no vents to make the attic a conditioned space.

Vented attic with spray foam. When we seal the attic with spray foam it s as tight as a butter tub. Using foam insulation for vented attics 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. Both low density open cell and medium density closed cell spray foam can be used in an unvented attic to provide the needed thermal resistance and airtightness. All insulation materials require proper venting.

Rigid foam and spray foam are two of them. Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope in this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within. Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof. Spray foam insulation in vented attics will resist any heat transfer from that airflow so you don t have to worry about the rest of your house getting hot as well.

Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. Earlier this year i got a question about a home that had spray foam insulation in the attic. Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space. A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits but then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents.

In a vented attic all of that expensive airflow is lost to the environment. The unvented attic space is considered the most effective and up to date building practice particularly by the spray foam industry. Nothing unusual about that. Spray polyurethane foam is a chemical product that is created by two materials isocyanate and polyol resin that will react with each other when they are mixed and will expand up to 30 to 60 times its liquid volume as it is sprayed in place.

By using an air impermeable insulation like spray foam on the roof deck will. This alternative to traditional building insulation fiberglass can be applied into wall cavities holes concrete slabs and even onto roof tiles and.