3 Benefits  of Rigid Insulation

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. plywood has an R-value of 1.25 and fiberglass batts have an R-value of 3.14). This is especially critical in preventing damage (such as mold and rot) to framing and walls in areas with extremely cold or damp climates. Since rigid foam is applied on the outside it also prevents thermal bridging. Thermal bridging happens when there is the loss of heat due to an interruption in the insulation by a material that is more conductive. This typically happens when interior insulation intersects things like stud frames or electrical boxes.

Better at controlling moisture: When it comes to controlling moisture, rigid foam serves two functions. It protects the wood sheathing or framing from any rain or water that leaks in under the siding. And it warms the interior sheathing or framing enough to prevent moisture accumulation from the heated interior air in the winter.

Better at preventing air leaks: When sealed with proper techniques and a suitable adhesive, rigid foam is an excellent air barrier. The same principle mentioned above that prevents thermal bridging also applies to air transfer. Unlike house wrap, which works to prevent infiltration (air coming into the building) but is poor at stopping exfiltration (air moving out of the building), rigid foam is able to do both.

Rigid Insulation Applications

Exterior Continuous Insulation: Rigid foam can be used as sheathing—a continuous layer of insulation on wall exteriors attached before the installation of house wrap and siding.

Basements: Indoors, rigid foam is the material of choice on walls where the insulation will be touching masonry. Mostly, this means the exterior walls in basement build-outs, except for daylight-facing walls, such as are found in walk-out basements. Rigid foam stands up to moisture better than fiberglass.

Radiant Heat Floors: Rigid foam is used as a thermal barrier underneath radiant floor heating systems.

Rim Joists: Rim joists around the edge of a foundation can be insulated with rigid foam blocks cut to fill the space and caulked in place. If concrete blocks have open cavities, they should be first stuffed with loosely packed fiberglass insulation.

Other Uses: Rigid foam can provide soundproofing to interior walls or to sequester interior spaces that are not climate controlled. Rigid foam can be used to build temporary privacy walls in shared apartments or dormitories.