Spray Insulation Roof Ventilation

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.

Spray insulation roof ventilation.

This illustration shows a sloped roof with cavity spray foam insulation sprayed on the underside of the roof deck and covered with sprayed on thermal or ignition barrier coating. For the same reason insulation shouldn t touch the roof s underside. 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. Nothing unusual about that.

Earlier this year i got a question about a home that had spray foam insulation in the attic. Rigid foam and spray foam are two of them. Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow.

Care should be taken with these assemblies particularly in cold climate zone locations i e. Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly. This alternative to traditional building insulation fiberglass can be applied into wall cavities holes concrete slabs and even onto roof tiles and. If spray foam is used a vent space may still be needed directly under the roof deck.

Moving the air control layer and thermal control layer to the underside of the roof deck has significant advantages in cases where the hvac system is located 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. Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof. Zones 5 6 7 and 8 in that the manufacturers of these materials assume that roof deck may require ventilation to assist drying.

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. The most important thing to remember is to use the correct type of insulation and to ensure it is installed correctly. Covering up the soffit vents with loose fill or batts which can happen if you stuff insulation along the eaves is a huge no no.