Rigid Foam Over Roof Sheathing

Johns manville r panel rigid roof insulation board offers r values of up to r 23 6 providing high thermal efficiency.

Rigid foam over roof sheathing.

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. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. I am in zone 7 and considering adding foam to the exterior since i am residing. Installed on the roof exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams.

Furring strips on sheathing behind rigid foam would installing vertical furring strips next to the sheathing and behind the rigid foam help the wall to breathe and still maintain r values. 4 of polyiso under 4 of eps all above the original roof sheathing. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space. 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.

Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing. 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. Thanks for any replys. 3 benefits of rigid foam sheathing.

Remove existing roofing and non adhered underlayment to expose roof sheathing. The illustration shows two layers of osb or plywood roof sheathing. Nail it around the edges with roofing nails. The exposed edges of the 3 layers of rigid insulation are no longer exposed.

Plywood has an r value of 1 25 and fiberglass batts have an r value of 3 14. 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. Then a second layer of plywood sheathing and asphalt shingles following the steps explained in this article. Or is this just over kill.

More effective insulation with r values ranging from 3 6 to 8 0 rigid foam sheathing has much better insulation per inch than other materials i e.