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.

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. Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize 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. 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.

I am in zone 7 and considering adding foam to the exterior since i am residing. Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing. 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. Thanks for any replys.

4 of polyiso under 4 of eps all above the original roof sheathing. The exposed edges of the 3 layers of rigid insulation are no longer exposed. Benefits of rigid foam on top of sheathing. Then a second layer of plywood sheathing and asphalt shingles following the steps explained in this article.

Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. 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. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space. Installed on the roof exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams.

3 benefits of rigid foam sheathing. Remove existing roofing and non adhered underlayment to expose 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. Johns manville r panel rigid roof insulation board offers r values of up to r 23 6 providing high thermal efficiency.

The illustration shows two layers of osb or plywood roof sheathing.