Rigid Foam Insulation Above The Roof Sheathing

Performance imperatives for high r value roof retrofit using insulating sheathing above the roof deck plus cavity insulation in roof framing.

Rigid foam insulation above the roof sheathing.

The main issue people encounter with insulation above sheathing is when it expands. 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. The glass fiber reinforcement contributes to improved fire performance and dimensional stability.

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. More insulation on the exterior is good. 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. Deck for a thick roof rigid foam insulation installed above the roof assembly can create an energy smart roof.

Polyisocyanurate insulation above the sheathing and approximately 91 4 in. Insulated roof assemblies can be vented or unvented. There are at least two good reasons why this approach makes more sense than installing the insulation under the roof sheathing. Plywood has an r value of 1 25 and fiberglass batts have an r value of 3 14.

3 benefits of rigid foam sheathing. With three layers of 11 2 in. However for the best performance and for when space comes at a premium it s tough to beat rigid foam insulation. High moisture areas may benefit from leaving a small air space between roof sheathing and the rigid foam insulation panels.

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. Over the foam you will need something to nail the roofing to usually a solid sheet of plywood or osb. 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. 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.

Roof edge detail overhang extended to hide the thickness of the over roofing rigid insulation. Gable end detail overhang cut and then rebuilt to hide the thickness of the over roofing rigid insulation. Products provide superior insulating properties.