Rigid Foam Under Roof Sheathing

Install it anywhere from the roof to the foundation.

Rigid foam under roof sheathing.

Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. Exterior foam sheathing is often installed on existing homes as an energy saving retrofit when new roofing or siding is needed. The boards are available in several thicknesses and r values. Install nailbase for cladding.

Rigid insulation is one of the best tools to reduce your energy costs. 1 inch and 2 inch thicknesses are common. Rigid insulation provides thermal protection and it can also serve as an air and moisture barrier. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.

Rigid foam insulation also known as insulating boards provide high r values. In my local area there is a green building consultant that recommends a ci panel which is basically eps foam glued to osb. Almost every house i see with exterior rigid foam in my online wonderings is covered with blue and pink xps the osb sheathing is nailed directly to the studs and is completely covered with the rigid foam. A leak free roof membrane that is fully adhered to the roof sheathing should be installed.

The way this is installed would be the osb to the exterior. You can even place it under the foundation slab. Nail it around the edges with roofing nails. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards.

Start at the bottom of the roof and place the first piece of rigid foam insulation against the metal flashing starting at the center line. They keep your home at a comfortable temperature without the need to crank your heat. The purpose of the requirement that rigid foam installed above roof sheathing meet certain minimum r values is to ensure that the roof sheathing stays warm enough during the winter to avoid moisture accumulation and possible sheathing rot. Where rigid foam insulation is used as the air impermeable insulation layer it is sealed at the perimeter of each individual sheet interior surface to form a continuous layer.