Rigid Foam Under Roof 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.

Rigid foam under roof sheathing.

Exterior foam sheathing is often installed on existing homes as an energy saving retrofit when new roofing or siding is needed. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize space. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards.

Installed a new fully adhered membrane to the top of the old board sheathing prior to adding all that rigid insulation. 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. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space. 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.

Install nailbase for cladding. Roof edge detail overhang extended to hide the thickness of the over roofing rigid insulation. 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. Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance.

Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. Rigid foam sheathing is a form of insulation continuous insulation to be exact that s applied to the exterior of the building. Continuous rigid insulation is a construction solution that provides a thermally efficient building enclosure.