How To Install Rigid Foam On Top Of Roof Sheathing

If you have a vented attic it makes no sense to install rigid foam above the roof sheathing.

How to install rigid foam on top of roof sheathing.

Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space. However if you want to use rigid foam in place of wood sheathing it needs additional bracing to prevent racking. If rigid foam sheathing is used on top of wood sheathing this doesn t matter. Nail it around the edges with roofing nails.

This retrofit assembly is appropriate for homes with conditioned attics or where the retrofit is intended to create a conditioned attic. The illustration shows two layers of osb or plywood roof sheathing. Updated on december 15 2017 with information on the u factor alternative. Benefits of rigid foam on top of sheathing.

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. Remove existing roofing and non adhered underlayment to expose roof sheathing. The exposed edges of the 3 layers of rigid insulation are no longer exposed. However most cathedral ceilings and.

A roof over a vented unconditioned attic does not need to include any insulation. Box beam gable framing new gable overhang is framed in the form of a box beam hanging off of a new layer of roof plywood roof sheathing cantilevered over the top of the 3 layers of rigid insulation. How to install rigid foam on top of roof sheathing. A vented attic is basically outdoors so installing rigid foam above your roof sheathing is a waste of money and a waste of rigid foam.

Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize space. Install insulating sheathing above the roof deck on existing homes. Installed on the roof exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams. Use the irc to determine foam thickness.

If the foam is too thin the roof sheathing will be cold which can lead to problems with condensation or moisture accumulation. You might as well put the rigid foam in the branches of a tree in your back yard.