What type of insulation is often applied as exterior sheathing?

Sheet insulation is commonly used as exterior sheathing due to its effectiveness in providing continuous insulation and thermal barriers in building envelopes. This type of insulation, typically made from materials like polystyrene or polyisocyanurate, offers several benefits when applied to the exterior of structures.

Firstly, it helps minimize thermal bridging, which occurs when conductive materials, like wood or metal framing, create pathways for heat transfer through the insulation. By installing sheet insulation on the exterior, the amount of heat loss or gain through these framing members is significantly reduced. This leads to more consistent indoor temperatures and improved energy efficiency.

Additionally, sheet insulation provides a protection layer to the underlying structure from environmental factors such as moisture and air infiltration. Its rigid nature helps mitigate air leaks, further enhancing the overall performance of the building's thermal envelope.

Other types of insulation, like spray foam or fiberglass batt, while effective in certain applications, are typically used in different contexts. Spray foam is more suited for filling gaps and providing an air seal, fiberglass batt is primarily used in between studs and joists, and blown-in insulation is usually employed for attic spaces or closed cavities. These applications do not align as closely with the primary role of exterior sheathing insulation as sheet insulation does.