Foam Insulation Roof Ventilation

The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow.

Foam insulation roof ventilation.

Zones 5 6 7 and 8 in that the manufacturers of these materials assume that roof deck may require ventilation to assist drying. Nothing unusual about that. In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof. Sometimes humidity levels spike in an attic after a spray foam job.

Rigid foam and spray foam are two of them. Foam insulation can play an important role in both vented and un vented roof assemblies. All insulation materials require proper venting. If a blower door test reveals that your spray foam insulation reduced ventilation beyond an acceptable level you may need to install one of these units in your home.

Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space. If spray foam is used a vent space may still be needed directly under the roof deck. Earlier this year i got a question about a home that had spray foam insulation in the attic. 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. Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. 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. This alternative to traditional building insulation fiberglass can be applied into wall cavities holes concrete slabs and even onto roof tiles and.

Care should be taken with these assemblies particularly in cold climate zone locations i e. For the same reason insulation shouldn t touch the roof s underside. Staple plastic or foam baffles to the roof sheathing near the eaves to keep the material away.