Venting The Roof Deck Above Foam Insulation

More insulation is needed above the roof deck in colder climates and where indoor relative humidity is above 35 in winter.

Venting the roof deck above foam insulation.

Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t any attic space. Similarly not everyone can afford to spray nearly 10 in. Nail 1 furring along every rafter side against the roof deck. Of open or closed cell spray foam in their roof or to stack a half foot of rigid foam on the roof deck.

All of these materials are supported by quality assurance testing capabilities that. 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. Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e.

If the attic space is going to be conditioned either for living or mechanical purposes or if a home design calls for a vaulted ceiling provision r806 3 in the international residential code calls for the roof deck above the space to be vented continuously from the eave to the ridge. Foam tech creates superior insulation and environmental control solutions by installing safe cost effective and environmentally friendly polyurethane foams. In the knee wall area the insulation is in the floor and on the. Cut and insert 1 or thicker high r foam insulation sheets r 8 per inch against the furring giving a 1 or greater air path between the insulation and the roof deck under the cathedral ceiling.

We have the capabilities to spray and inject a variety of foam systems to achieve a high r value while providing both effective vapor and air barriers. Attach this roof and attic insulation treatment using foam baffles to ventilate insulate and channel cold and hot air to roof vents before insulation is add. High r value unvented roof assemblies will require a proportionally larger amount of insulation above the roof deck for condensation control. 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.

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. Generally 40 of the total assembly r value should be above the roof deck. Heat from the house rises up to the attic but when there isn t one the heat rises up to the roof.