Spray Foam Insulation In Vented Attic

Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space.

Spray foam insulation in vented attic.

Image courtesy of d7 spray foam insulation houston tx using spray foam insulation in an unvented attic application. By using an air impermeable insulation like spray foam on the roof deck will. Earlier this year i got a question about a home that had spray foam insulation in the attic. 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.

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. An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. Unvented attics sometimes called sealed enclosed or encapsulated attics feature insulation on the underside of the roof decking rather than on the attic floor. However in a traditionally insulated attic insulation on the ceiling the attic is vented.

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. Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. Nothing unusual about that. In comparison to high density spray foam medium density spray foam is applied as a low or high pressure two component polyurethane spray foam.

All insulation materials require proper venting. 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 type of spray foam offers the specific benefits of continuous insulation interior wall cavity fill and unvented attic applications. 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.

The unvented attic space is considered the most effective and up to date building practice particularly by the spray foam industry. 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.