Rigid Foam Roof Sheathing

Exterior rigid foam improves air tightness adds r value reduces the chance of condensation in wall cavities and greatly reduces thermal bridging through studs.

Rigid foam roof sheathing.

1 inch and 2 inch thicknesses are common. Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize space. Remove existing roofing and non adhered underlayment to expose roof sheathing. Foamular 150 1 1 2 in.

Foamular 250 2 in. 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. 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. Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency.

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. It spans the rafters to support the roofing and in the case of panel sheathing such as plywood or osb it acts as a diaphragm with the walls to resist horizontal loads. 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.

R 10 scored squared edge insulation sheathing. Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space. Not only that foam sheathing will soon be mandated by code in some climate zones.

Foamular 150 1 in. The boards are available in several thicknesses and r values. R 7 5 scored squared edge rigid foam board insulation sheathing. If you have a vented attic it makes no sense to install rigid foam above the roof sheathing.

Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. 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. You might as well put the rigid foam in the branches of a tree in your back yard.