Rigid Insulation Over Roof Sheathing

The exposed edges of the 3 layers of rigid insulation are no longer exposed.

Rigid insulation over roof sheathing.

The exposed edges of the 3 layers of rigid insulation are to be sealed with another layer of membrane. This type of insulated roof assembly limits thermal bridging through rafters after installing several layers of rigid foam above the roof sheathing. 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. Zip system r sheathing is the simple all in one structural panel with built in exterior insulation.

1 inch and 2 inch thicknesses are common. Nail it around the edges with roofing nails. Install nailbase for cladding. Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance.

Exterior rigid foam improves air tightness adds r value reduces the chance of condensation in wall cavities and greatly reduces thermal bridging through studs. Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. Foam board sheathing insulation johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency. One of the most efficient and popular methods though is to install rigid foam insulation on top of roof sheathing.

Featuring integrated moisture air and thermal protection zip system r sheathing completely reimagines traditional wall assemblies by streamlining exterior water air and thermal management. Most home and business owners opt for rigid foam on top of roof sheathing because it makes the most sense and it s an eco friendly solution. Polyurethane spray foam metal roof insulation in order to add moisture barrier under metal roof you can spray the undersides of the roof by using a thick layer of polyurethane spray foam. The boards are available in several thicknesses and r values.

It makes the most sense and preforms the best under most conditions. It will help you to eliminate problems that may come when the house becomes extremely cold in the winter and terribly hot in the summer. A roof over a vented unconditioned attic does not need to include any insulation. Rigid insulation provides thermal protection and it can also serve as an air and moisture barrier.

Not only that foam sheathing will soon be mandated by code in some climate zones. 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. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards. Nailbase must be vented in high snow load areas.