Foam Insulation Underside Of Roof

This can happen when the roof becomes damaged on the outside and water gets into the space between the spray foam and the underside of the slates.

Foam insulation underside of roof.

The osb got wet and rotted. Will your shingle manufacturer void their warranty if any form of insulation is directly to the underside of the roof. 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. It will help you to eliminate problems that may come when the house becomes extremely cold in the winter and terribly hot in the summer.

If yes consider doing a cold roof which uses baffles to leave an inch of air flow between the seal of to the inside of the house and the roof sheething like a roof under a roof. In addition to installing the foam board on the underside of the roof deck you can attach it to the bottom edges of the rafters in the same manner you would hang drywall. Some houses with open cell spray foam installed on the underside of the osb roof sheathing have had moisture problems. But where does the moisture come from.

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. 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. 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. You may also need to inspect the foam at intervals to see whether any shrinkage has.

The authors of the first paper cited a study in south carolina where the relative humidity in the attic was way too high in summer 80 to. Even small gaps can allow the passage of warm air through the foam rendering the foam all but useless as an insulator.