Polyisocyanurate

Polyisocyanurate, also referred to as PIR, polyiso, or ISO, has the highest R-value of any rigid foam board insulation commercially available.  It comes with a variety of backers (foil, fiberglass mat, vinyl, and paper), and is very similar to the polyurethane used by spray foam contractors.  It is best suited for use in walls, ceilings, and roofs where high R-values are desired in a limited space.

Extruded Polystyrene

Extruded polystyrene, also referred to as XPS, is the most recognizable rigid foam board insulation on the market today and comes in a variety of colors (blue, pink, green, gray) depending on the brand. It is especially suited for use below grade as concrete footer and foundation insulation as well as under concrete slab with in-floor radiant heat systems.

Expanded Polystyrene

Expanded polystyrene, also referred to as EPS, white board, and bead board, has the lowest R-value of the three rigid foam board insulation types, but is the most economical and versatile.  It can be used anywhere insulation is needed.  It performs well as insulation for garages, pole barns, basements, and crawl spaces. It is also commonly used below grade as concrete footer and foundation insulation as well as under concrete slab with in-floor radiant heat systems.  Commercially it is used on low slope roofs, under stucco, and even as a soil substitute in road construction (sometimes called geofoam). It is simple to cut and shape with common tools, has an excellent bond with drywall and non-solvent type adhesives, resists moisture penetration, does not support bacterial growth, and is mold resistant.