Exterior Basement Insulation

If your remodeled basement isn’t already insulated then you really should consider insulating it in order to save on energy bills in your home, the same can also be true of simply improving the insulation in your basement. The cost of efficiently insulating the basement will be paid back within a few years, due to savings on your energy bills.

Another reason for improving the insulation of your basement could be to convert it into an area that can become part of the living space in your home, rather than just a utility or junk area. When insulating a basement relatively few people think about the exterior basement insulation options and only insulate inside the basement.

What is Exterior Basement Insulation

A basement is typically an underground room with seven to ten foot high walls rising from the foundations of the building. Exterior basement insulation does not mean having to excavate all the earth from beside the exterior basement walls and insulating them.

Exterior basement insulation can be applied to just the proportion of the basement wall that might be above ground level, usually less than 25% of the wall. There are two types of insulation materials used for external basement walls: Reflective Insulation and Rigid Insulation.


Quite simply the heat loss from an un-insulated basement can be as great as the heat loss from an un-insulated attic, whilst the portion of an exterior basement wall below ground level will benefit slightly from the insulating properties of the surrounding soil; an exposed portion of the wall will leak heat as badly as if you’ve left a window open.

Also, don’t forget, heat rises, so any warm air in the basement will naturally rise to top and come into contact with the colder air at the top. The net result of this will be condensation.

As well as retaining heat in your basement you’ll want to avoid condensation, so having effective and equalized insulation throughout the basement is essential. Don’t forget as well that effective insulation will help to keep the basement cool in the summer, so there’ll be no need to fit an air-con unit down there.

Reflective Insulation Materials

These prevent heat loss by reflecting heat (radiant energy) back into the basement. The material used for this form of exterior insulation is a sandwich of two layers of Aluminum foil with either a layer of foam or plastic bubble-sheet in between them. Very light, flexible and strong, it can be nailed, stapled or glued onto the exterior basement wall.

As well as providing heat insulation the foil will also add to the soundproofing properties of the basement wall. The foil is entirely weather-proof in its own right; however, after installing it you might want to consider adding a layer of cladding over it any area exposed above ground level - perhaps faux stone panels? Not only will this add another layer of weather-proofing and insulation, but will also disguise what will otherwise appear to be a rather ‘stark’ foil wrapping around the wall.

Rigid Insulation Materials

To prevent heat loss by conduction and convection rigid foam boards can be fixed to the exterior walls of a basement. The foam itself can come in three forms: expanded polystyrene, extruded polystyrene or the relatively new polyiso. Accordingly the three materials increase in both price and insulating properties, with polyiso being the best.

These rigid products are both lightweight and easy to install. The foam boards themselves can be fitted with nails, staples or glue to a stud framework, with any joints being sealed with an aluminum foil tape. The same as with a reflective insulator, the rigid foam insulation can then be disguised with a cladding.