Can I Put Foam Board Right Over Cinder Block to Insulate My Garage?

Materials

• According to the Energy Savers website, the two most common materials used to make foam board insulation are polystyrene and polyisocyanurate. Polystyrene is an efficient material for making foam board insulation for your garage, because it has an R-value of around 5 per inch. The R-value is a number used to indicate a material's resistance to heat flow per inch of material. The R-value for polyisocyanurate can vary, but it can reach as high as 9 per inch if a layer of reflective insulation material is added to a polyisocyanurate board.

Double Glazing

• You can improve the efficiency of foam board insulation over your cinder block garage walls by doing what is known as double glazing. You place a layer of polyurethane sheets over your cinder block walls and then mount wooden wall studs directly to the blocks. The foam insulation sheets would go over the studs, creating a space between the polyurethane and the foam insulation. The air in this space helps to prevent warm air from leaving your garage and keeps cold air out.

Thermal Lining

• Polyisocyanurate foam panels that have an extra layer of reflective insulating material can create the same effect as double glazing but without the added work of wooden wall studs and polyurethane sheeting. The foam insulation panels can be affixed directly to the garage cinder block wall using a strong adhesive. The reflective layer of material acts as a secondary lining that can help regulate the temperature in the garage.

Finishing Work

• If you plan on putting paneling or drywall over foam board insulation that has been installed over your cinder block garage walls, you have two solutions. You can install wooden wall studs directly to the cinder block wall, as previously mentioned, and hammer or screw finishing work into the studs. The other alternative is to build wall frames on top of the insulation and attach your finishing work to the frames.