Spray Foam Insulation On Roof Sheathing

Open or closed cell spray foam is applied to the underside of the roof sheathing and additional fiberglass or cellulose insulation is blown in as a cost saving method for meeting high insulation requirements and filling in the cavity space between the rafters to the ceiling deck.

Spray foam insulation on roof sheathing.

I m constructing a new home along the rhode island shore. 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. There are at least two good reasons why this approach makes more sense than installing the insulation under the roof sheathing. Moisture from indoors can diffuse through the foam and find the cold roof sheathing where it accumulates and eventually rots the roof.

Both papers basically came to the same conclusion. 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. A number of factors should be taken into consideration when choosing between these two especially the climate zone that you re building in. Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly.

When installing attic insulation a case can be made for both radiant barrier sheathing with typical types of insulation as well as spray foam insulation. There have been isolated moisture related incidents that raise potential concerns about the overall hygrothermal performance of these systems. Open cell spray polyurethane foam ocspf or closed cell spray polyurethane foam ccspf insulation is sprayed along the underside of the roof sheathing to provide a unvented insulated and conditioned attic space or roof assembly that can be resilient durable and efficient in all climate zones. Insulated roof assemblies can be vented or unvented.

Radiant barrier sheathing is inexpensive and reflects thermal radiation to keep attic spaces cool. The roofing materials are installed and consist of timberline shingles and full coverage ice and water barrier the entire roof. Open cell spray foam insulation is risky in all climate zones we already know open cell spray foam is risky in cold climates. 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 can be accomplished by installing sturdy site built ventilation baffles in each rafter bay made for example by installing 1 x1 sticks and thin. 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.