Rigid Foam Over Roof Sheathing

Not only that foam sheathing will soon be mandated by code in some climate zones.

Rigid foam over roof sheathing.

Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards. Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space.

The boards are available in several thicknesses and r values. 1 inch and 2 inch thicknesses are common. Exterior foam sheathing is often installed on existing homes as an energy saving retrofit when new roofing or siding is needed. Add air conditioning to premises on second floor with a split unit.

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. 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 insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. Rigid insulation provides thermal protection and it can also serve as an air and moisture barrier.

Install nailbase for cladding. 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. Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize space. The exposed edges of the 3 layers of rigid insulation are no longer exposed.