Foam Insulation No Roof Vent

The movement of air into indirect conditioning of an unvented attic is a slow gradual process that will not be noticeable by occupants and typically will not put any strain on the hvac system.

Foam insulation no roof vent.

Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space. All insulation materials require proper venting. In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof. One of the most common reasons to put spray foam on the roofline is to avoid having to air seal the attic floor because the attic is connected with the air in the house and indoor air is more humid than outdoor air which can cause moisture problems.

It has been said that insulating with spray foam insulation at the roof line will lead to moisture problems with the roof sheathing. The principle behind soffits is to allow air to circulate in and around the attic. 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. Foam insulation can play an important role in both vented and un vented roof assemblies.

You don t need soffit or gable vents either since the attic is now conditioned 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. In most residential homes the soffit and associated vents is the structural part of the roof that hangs over the side of the home. 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.

Insulating and venting when there is no roof soffit. There is no need for a ridge vent in this application since the ccspf seals the roof. Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof.