Roof Venting With Spray Foam Insulation

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.

Roof venting with spray foam insulation.

Unless you re bulk filling rafter bays between 2 10 or 2 8 rafters with closed cell spray foam this approach will likely require you to fur out the rafters to accommodate additional insulation to achieve desired r values. This alternative to traditional building insulation fiberglass can be applied into wall cavities holes concrete slabs and even onto roof tiles and. All insulation materials require proper venting. While fiberglass insulation is an excellent and effective product for insulating most building cavities in areas where there is extra risk of trapping moisture and thus rot or mold infections such as crawl spaces and cathedral ceilings where roof venting may be absent or minimal we prefer to use closed cell foam insulation products or spray.

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. For best performance the airspace in the vent chute should be a minimum of 2 in. Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space. But today i m focusing on roofers because of something i saw recently.

Attic ventilation and spray foam don t mix. 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. Spray foam insulation can even be applied with roof vents. Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof.

However many people think that roof vents cannot be used in conjunction with spray foam insulation. Roof vents are great for allowing air to move and for removing toxic odours from the home. They could be in any trade really insulation hvac drywall. Rigid foam and spray foam are two of them.

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.