Rigid Foam Under Metal Roof On Purlins

Basically speaking ignoring sub insulated roofs which are a special case with rigid foam board insulation directly under the metal roofing the roofing needs proper support to be able to handle snow ice loads wind loads and walking on during installation cleaning and maintenance.

Rigid foam under metal roof on purlins. The best material for use with metal roof insulation is in the form of foam batting. This foam can be used on either the outside or the inside of the sheathing. I am getting ready to put a metal roof on my house it presently has 1 layer of shingles on a 6 12 pitch and iam in florida i am think of putting r foil under 1 x 4s battens or the styrofoam boards between the battens and also a solar attic fan w elec option and the metal will be a light color from douglas metal roofing does this sound like a. This will provide an air space above the foam insulation to improve ventilation on the underside of the metal roofing.

Commonly these use metal deck panels over the roof structure thus supporting the insulation and a vapor retardant material on top of the deck. In this insulation approach rigid foam insulation board is used to achieve the sought after energy performance. Then a second layer of plywood sheathing and asphalt shingles following the steps explained in this article. 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.

Avoids nails or screws which could penetrate the metal roof and cause leaks. This is different from the normal roll up type of insulation as it comes in panels rather than paper covered fiberglass. Will that be a concern with metal roofing. Use rigid foam insulation to cover wider spans of roof sheathing between joists.

Purlins are 2 by 4 feet and are installed much like metal roofing. 4 of polyiso under 4 of eps all above the original roof sheathing. First nail 1x2s to the rafter sides up against the roof strapping. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.

Metal roof purlins are installed horizontally under metal roofs. Plywood sheathing then roofing felt than 1 5 rigid foam metal roofing. Cut each sheet to the desired size using a utility knife then fasten it in place using staples or adhesive. Insulating with spray foam insulation.

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. It is possible to insulate from below as you suggest with rigid polystyrene insulation. I have a 90 year old stone cottage in portland oregon.