Rigid Foam Under Metal Roof On Purlins

The best material for use with metal roof insulation is in the form of foam batting.

Rigid foam under metal roof on purlins.

Further insulation may be added by the use of high r foam boards placed beneath the purlins. First nail 1x2s to the rafter sides up against the roof strapping. 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 has to be installed on plywood osb or possibly purlins.

Commonly these use metal deck panels over the roof structure thus supporting the insulation and a vapor retardant material on top of the deck. If you want to be sure talk to your roofer or the manufacturer of the roofing panels. This foam can be used on either the outside or the inside of the sheathing. Cut each sheet to the desired size using a utility knife then fasten it in place using staples or adhesive.

In this insulation approach rigid foam insulation board is used to achieve the sought after energy performance. As far as i know standing seam metal roofing can t be installed on rigid foam. The solution i have in mind is to cut 2 foot wide strips of 1 2 thick foil poly faced eps to fit between the purlins 1 2 below the metal roofing. I would seal the eps against the purlins with a high grade permanently flexible caulk or spray foam insulation.

Oh i forgot to mention purlins are best placed 24 inches on center to fit with the most common insulation width and insulation between purlins should be unfaced. Rigid board composite systems. This is different from the normal roll up type of insulation as it comes in panels rather than paper covered fiberglass. Use rigid foam insulation to cover wider spans of roof sheathing between joists.

This will provide an air space above the foam insulation to improve ventilation on the underside of the metal roofing. Insulating with spray foam insulation. The rigid board material costs roughly 23 cents per square foot. Avoids nails or screws which could penetrate the metal roof and cause leaks.

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.