Rigid Foam Over Roof Sheathing

Plywood has an r value of 1 25 and fiberglass batts have an r value of 3 14.

Rigid foam over roof sheathing.

Apply continuous air control membrane to existing roof sheathing or implement continuous air control at 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. Installed on the roof exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space.

A lower layer conventionally nailed to the rafters and an upper layer installed as a nailing surface for the roofing material on top of the rigid foam. Then a second layer of plywood sheathing and asphalt shingles following the steps explained in this article. 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. Benefits of rigid foam on top of sheathing.

Remove existing roofing and non adhered underlayment to expose roof sheathing. I am in zone 7 and considering adding foam to the exterior since i am residing. 4 of polyiso under 4 of eps all above the original roof sheathing. Johns manville r panel rigid roof insulation board offers r values of up to r 23 6 providing high thermal efficiency.

R panel is manufactured with a closed cell polyisocyanurate foam core bonded to fiberglass reinforced facers and designed for use over metal nailable and non nailable roof decks with a variety of membrane systems. 3 benefits of rigid foam sheathing. Or is this just over kill. Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize space.

Thanks for any replys. Nail it around the edges with roofing nails. The exposed edges of the 3 layers of rigid insulation are no longer exposed. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers.

We live in zone 5 suburb of chicago and are hopefully about to put rigid foam above the roof sheathing on just the northeast roof portion of our roof.