Rigid Foam Roof Sheathing

The boards are available in several thicknesses and r values.

Rigid foam roof sheathing. Rigid insulation provides thermal protection and it can also serve as an air and moisture barrier. 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 sheathing 3. Alterations to roof ceiling wall or floor cavities which are insulated to full depth with insulation having a minimum nominal value of r 3 0 in.

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 foam insulation packs a lot of r value into a thin package but not all rigid foam performs the same. Metal panel on metal framing figure a 1. 1 inch and 2 inch thicknesses are common.

Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency. Install nailbase for cladding. Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers.

Not only that foam sheathing will soon be mandated by code in some climate zones. One of the keys to over roofing is to tie the air control layer of the roof assembly to the air control layer of the wall assembly. Exterior rigid foam improves air tightness adds r value reduces the chance of condensation in wall cavities and greatly reduces thermal bridging through studs. You can even place it under the foundation slab.

Cold formed metal framing c. This foam is applied over the top of the membrane that came down from the roof deck catching the wall control layers. Install it anywhere from the roof to the foundation. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards.

Detail roof wall intersection and all openings and penetrations to provide a continuous air barrier system. Replacement of a roof membrane where either the roof sheathing or roof insulation is not exposed or if there is existing roof insulation below the roof deck. On the gable ends this was pretty easy. Rigid insulation is one of the best tools to reduce your energy costs.