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Foam Board Insulation Types

I’ve written several posts about how to insulation basement walls in which I promote the use of foam board insulation as the first line of defense against moisture and mold. Because of this I often get questions about which type of foam board insulation to use and what R values these products provide.

There are three basic foam board insulation products on the market produced under several different manufacturer names. They include expanded polystyrene, extruded polystyrene,  and polyisocyanurate unfaced or foil faced.

Expanded Polystyrene Foam

Expanded polystyrene foam (EPS) is the cheapest and least used foam board insulation product on the market. This product typically has an R value of 3.6 to 4.0 per inch of thickness. Expanded polystyrene insulation is similar to the foam used for packing “peanuts” and it’s typically used for insulated concrete forms also knows as ICF’s. It is also sometimes used on commercial buildings for roof and wall panel insulation which is typically sandwiched between light gauge metal.

Cost = Cheapest of the foam insulation boards.

Extruded Polystyrene Foam

Extruded polystyrene foam (XPS) also known as blue board or pink board comes in many different thicknesses and edge profiles. This insulation board is probably one of the most widely used foam board insulation products in the residential construction industry. XPS has an R value of 4.5 to 5.0 per inch of thickness.

This is the product that I typically use to insulate basement walls. It’s reasonably priced, light weight and easy to use. This product is also used to insulate the outside of foundation walls and even under slabs.

Cost = This product is the middle of the road for these types of foam board insulation products.

Polyisocyanurate

Polyisocyanurate also known as polyiso is seen in all kinds of commercial building applications and more recently with residential building projects. Polyiso is typically used with a foil facing and it has an R value of 7.0 to 8.0 per inch of thickness. The reflective foil facing makes it an excellent insulation board when radiant heat is involved. The foil facing also makes it very easy to seal with good quality foil faced tapes.

Cost = Polyiso is the most expensive of the foam board insulation products however it’s the highest R value.

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