Rigid Foam Insulation Above The Roof Sheathing

Roof edge detail overhang extended to hide the thickness of the over roofing rigid insulation.

Rigid foam insulation above the roof sheathing.

The glass fiber reinforcement contributes to improved fire performance and dimensional stability. Of cellulose insulation in the rafter cavities the roof shown here has an r value of approximately 63. The following measures are necessary to ensure high levels of performance for this roof retrofit strategy. Products provide superior insulating properties.

Deck for a thick roof rigid foam insulation installed above the roof assembly can create an energy smart roof. 3 benefits of rigid foam sheathing. Installed a new fully adhered membrane to the top of the old board sheathing prior to adding all that rigid insulation. Over the foam you will need something to nail the roofing to usually a solid sheet of plywood or osb.

Foamular extruded polystyrene xps rigid foam insulation offers foamular extruded polystyrene xps rigid foam insulation offers a comprehensive line of products choose the strength you need from 15 to 60 psi and exceptional moisture resistance. There are lots of different ways to insulate this type of roof but one of the best methods calls for the installation of rigid foam insulation above the roof sheathing. However for the best performance and for when space comes at a premium it s tough to beat rigid foam insulation. Effective water control is essential to the performance of any attic roof system.

Polyisocyanurate insulation above the sheathing and approximately 91 4 in. Gba taught you that it s a great idea to install rigid foam on the exterior side of your wall sheathing as long as a the rigid foam is thick enough to keep your sheathing above the dew point during the winter and b your walls don t have any interior polyethylene. High moisture areas may benefit from leaving a small air space between roof sheathing and the rigid foam insulation panels. To save a step i would recommend using a nailbase panel foam preadhered to osb or sometimes plywood on one side only see photo facing page.

Insulated roof assemblies can be vented or unvented. Gable end detail overhang cut and then rebuilt to hide the thickness of the over roofing rigid insulation. There are at least two good reasons why this approach makes more sense than installing the insulation under the roof sheathing. Thermax sheathing is a non structural rigid board insulation consisting of a glass fiber infused polyisocyanurate foam core laminated between 1 0 mil smooth reflective aluminum facers on both sides.

With three layers of 11 2 in. More insulation on the exterior is good. 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.