Spray Polyurethane Foam On The Underside Of Your Roof Sheathing

There have been isolated moisture related incidents that raise potential concerns about the overall hygrothermal performance of these systems.

Spray polyurethane foam on the underside of your roof sheathing.

This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4. No airsealing hence i want to remove the fiberbatts and spray 3 inches of closed cell spray foam in before putting the fiberbatts back in place. 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. Open cell spray polyurethane foam or closed cell spray polyurethane foam ccspf insulation can be sprayed along the underside of the roof sheathing to provide a conditioned and insulated attic space that can be durable and efficient in all climate zones see figure 1.

Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly. The osb got wet and rotted. Some houses with open cell spray foam installed on the underside of the osb roof sheathing have had moisture problems. You must meet the same minimum code requirements for the spray foam layer and the total assembly as for the rigid foam plus air permeable insulation approach.

The roofing materials are installed and consist of timberline shingles and full coverage ice and water barrier the entire roof. But where does the moisture come from. Polyurethane or polystyrene spray foams can provide thorough coverage to roof rafters and attic walls in much less time than is needed for other materials. The attic will be a conditioned space and i m planning to apply spray foam insulation to the underside of the roof sheathing.

Unvented roof strategies with open cell and closed cell spray polyurethane foam insulation sprayed to the underside of roof sheathing have been used since the mid 1990 s to provide durable and efficient building enclosures. The attic is unvented for instance no ridge vent exists. I have a conditioned attic currently insulated with r19 fiberbatts between the rafters. If you are installing spf on the walls of the crawlspace then you need to leave an inspection strip around 6 wide on the walls.

Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.