Foam Insulation Underside Of 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.

Foam insulation underside of roof.

You may also need to inspect the foam at intervals to see whether any shrinkage has. But where does the moisture come from. 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. This can cause condensation due to the temperature difference between in this space compared to the rest of the loft room.

To get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. 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. 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. 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.

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. Even small gaps can allow the passage of warm air through the foam rendering the foam all but useless as an insulator. Some houses with open cell spray foam installed on the underside of the osb roof sheathing have had moisture problems. Will your shingle manufacturer void their warranty if any form of insulation is directly to the underside of the roof.

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. The osb got wet and rotted.