Foam Insulation No Roof Vent

Better to have a vent channel and no vent openings than vice versa as the air gap allows some evaporative drying and hygric redistribution.

Foam insulation no roof vent.

The principle behind soffits is to allow air to circulate in and around the attic. To add to what brian said closed cell spray foam ccspf applied directly to the underside of the roof sheathing would seal a ridge vent shut. However second only to an unvented closed cell foamed roof with bituthene membrane a vented roof with fibrous insulation and no vent channel from soffit to ridge is a recipe for disaster. Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof.

In a vented roof foam can seal the openings and serve as an air barrier and a vapor retarder in addition to its insulating function. All insulation materials require proper venting. There is no need for a ridge vent in this application since the ccspf seals the roof. You don t need soffit or gable vents either since the attic is now conditioned space.

In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof. Insulating and venting when there is no roof soffit. In most residential homes the soffit and associated vents is the structural part of the roof that hangs over the side of the home. Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space.

But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used. It has been said that insulating with spray foam insulation at the roof line will lead to moisture problems with the roof sheathing. Rigid foam and spray foam are two of them.