Rigid Foam Exterior Roof Sheathing

Exterior foam sheathing is often installed on existing homes as an energy saving retrofit when new roofing or siding is needed.

Rigid foam exterior roof sheathing.

If you have a vented attic it makes no sense to install rigid foam above the roof sheathing. Rigid foam sheathing is a form of insulation continuous insulation to be exact that s applied to the exterior of the building. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards. Continuous rigid insulation is a construction solution that provides a thermally efficient building enclosure.

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. Not only that foam sheathing will soon be mandated by code in some climate zones. Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. Nailbase must be vented in high snow load areas.

Rigid foam must be thick enough to prevent condensation on the roof sheathing. A vented attic is basically outdoors so installing rigid foam above your roof sheathing is a waste of money and a waste of rigid foam. Foamular family of products brochure pdf v 1588677951000 7 13 mb. Foamular insulating sheathing is xps insulation is used as sheathing over all exterior walls in wood or metal framing construction to create an effective insulating envelope over the entire structure.

By patrick mccombe issue 273 feb mar 2018 when combining exterior foam insulation with fiberglass cellulose or mineral wool roof insulation the foam layer must be thick enough to keep the sheathing temperature above the dew point. You might as well put the rigid foam in the branches of a tree in your back yard. Exterior rigid foam improves air tightness adds r value reduces the chance of condensation in wall cavities and greatly reduces thermal bridging through studs. Install nailbase for cladding.