Foam Insulation Board Over Windows

For the foam sheathing to be an effective air barrier and provide the drainage plane the joints between the boards must be sealed.

Foam insulation board over windows.

Flash the sheathing around the buck to the window opening with tape or liquid flashing before installing the exterior foam insulation. Even with all the joints sealed it is still not recommended to have a vertical joint in the sheathing occur over a window head. One common use of extruded polystyrene foam board is for foundation insulation panels. If your building has outie windows you should use the rigid foam or housewrap installed on the exterior side of the rigid foam as your wrb.

There are basically two types of reflective insulation that can be used by homeowners today. Prepare a rough opening for a nail fin window over exterior rigid foam insulation. The first is a foam backed foil that is much like the blue foam insulation used on a home s outer shell. This is an even more dense and more expensive foam board insulation.

Polyiso comes in several thicknesses and is used over house sheathing underneath siding or in attic spaces where its reflective properties are very effective. Insulating boards are just one of the many types of foam insulation. When to use foam board insulation. The layout of the sheathing board over the wall area should be done with this in mind.

Polyisocyanurate is another option coming in as the densest and more expensive option for foam board. It comes in sheets the same size as plywood and is easy to work with. It provides an r value of 6 per inch of thickness and often comes foil faced to help reflect radiant heat. If you choose asphalt felt or housewrap it should be installed between the wall sheathing and the rigid foam.

Instead you should use zip sheathing asphalt felt or housewrap as your wrb.