How To Install Rigid Foam On Top Of Roof Sheathing

Nail it around the edges with roofing nails.

How to install rigid foam on top of roof sheathing.

How to install rigid foam on top of roof sheathing. Use the irc to determine foam thickness. This retrofit assembly is appropriate for homes with conditioned attics or where the retrofit is intended to create a conditioned attic. Install insulating sheathing above the roof deck on existing homes.

Remove existing roofing and non adhered underlayment to expose 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. A roof over a vented unconditioned attic does not need to include any insulation. The illustration shows two layers of osb or plywood roof sheathing.

If you have a vented attic it makes no sense to install rigid foam above the roof sheathing. Slightly more expensive adding a layer of rigid foam on top of plywood or osb sheathing will increase the cost of the project. 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. Updated on december 15 2017 with information on the u factor alternative.

Many homes in more urban areas or other places with dense populations are opting for this method because they can better optimize space. If rigid foam sheathing is used on top of wood sheathing this doesn t matter. The exposed edges of the 3 layers of rigid insulation are no longer exposed. However if you want to use rigid foam in place of wood sheathing it needs additional bracing to prevent racking.

However most cathedral ceilings and. Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space. Benefits of rigid foam on top of sheathing. If the foam is too thin the roof sheathing will be cold which can lead to problems with condensation or moisture accumulation.

Start at the bottom of the roof and place the first piece of rigid foam insulation against the metal flashing starting at the center line. 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.