Installing Rigid Foam Over Roof Sheathing

Foam sheathing can help protect walls from moisture problems but only if it is thick enough and installed properly.

Installing rigid foam over roof sheathing.

Interior moisture can enter the wall from air leaks or diffusion through the wall finish. To lessen heat buildup in the summer we installed dupont tyvec attic wrap on the top of the rafters and then nailed 1 furring strips on top of the rafters then installed the. The plywood was fastened through the rigid foam to the rafters with long screws. Measure the depth of the rigid foam.

Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. Rigid foam over roof sheathing we are in the process of building a home with all the ceilings in the house paralell to the roof and used 2 x 10 rafters throughout. This type of insulated roof assembly limits thermal bridging through rafters. 1 use a thick enough layer of foam to minimize condensation on its interior face.

Exterior foam sheathing is often installed on existing homes as an energy saving retrofit when new roofing or siding is needed. Box beam gable framing new gable overhang is framed in the form of a box beam hanging off of a new layer of roof plywood roof sheathing cantilevered over the top of the 3 layers of rigid insulation. Use a straight edge knife or utility knife to cut the panels to size. There are three key issues with foam sheathing.

You can install rigid foam on the inside of a wall as well but adding exterior foam increases the r value of a wall or roof without eating up interior living space. For extra protection dab a small amount of caulk over each nail used to secure the rigid foam insulation to the plywood. Rigid foam offers tremendous boost to a home or office s r value. A helpful hint for installation is to use a straight edge along the cut line to ensure the panels fit best.

The exposed edges of the 3 layers of rigid insulation are no longer exposed. If you are building a new home there are two basic ways to install rigid foam on the exterior of a wall. To serve as a drainage plane the seams in the foam sheathing must be properly taped with sheathing and flashing tapes to provide continuity of the drainage plane at joints between panels. When rigid foam insulating sheathing is installed on the exterior walls of a home the foam can serve as a drainage plane taking the place of house wrap for time and cost savings.

Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. Install nailbase for cladding. You may need to buy longer roofing nails to reach the plywood through the.