Options for Insulating Your Basement

by Murray Anderson

During the winter does your main floor feel cool? Do you often find yourself turning up the thermostat to try to keep your home comfortable? Well the cause of your problem and the reason your heating bills are so high could be just below your feet - an uninsulated basement. According to the US Department of Energy, you could be losing as much as 30% of the heat in your home through an uninsulated basement. When it comes to insulating your basement, there are three proven methods, insulating the ceiling, insulating the exterior of your foundation walls or insulating the interior of your basement walls.

Insulating the basement ceiling

This is by far the easiest and quickest way to insulate your basement. Simply install fiberglass bats between the floor/ceiling joists in the basement. Since floor joists are commonly 16” on center and made from 10” lumber you can install up to 10” of fiberglass insulation (approximately R-30) between the joists. Fiberglass bats can be cut to length and then pressure fit in between the joists to provide insulation on the underside of your main floor, and helping keep it warm and comfortable.
The downside to this method is primarily cost (covering the entire floor with up to 10”of insulation can be pricey, and by insulating the basement ceiling you are effectively eliminating potential development of your basement space in future. (Similar to the way the space in your attic above your ceiling joists is unlikely to be developed).

Insulating the exterior foundation walls

This is a highly effective way to insulate your basement, however, it's usually done when a home is under construction and it becomes a major project in an existing home since it is time consuming, labor intensive and expensive.
Insulating your basement exterior requires digging a trench around your foundation, applying rigid glass fiber or polystyrene boards directly to the walls then carefully back filling the excavation.
Once the job is completed, you not only have a warmer basement, your basement will be much drier and healthier since the exterior insulation also helps block any moisture intrusion through the walls of the foundation.

Insulating the interior walls

This is by far the most popular way of insulating a basement since it is a job a confident DIY'er can take on, relatively inexpensive and perhaps most important for many people, allows for future development of the basement space for things such as a home office, bedrooms or even a media room..
Insulating the interior basement walls involves building stud walls (wood or metal) around the exterior of the basement, installing insulation either between the studs or directly on top of them and then covering the insulation with a plastic vapor barrier and drywall.
When insulating the interior basement walls it's important there is no moisture getting into the basement so ensuring proper drainage around the perimeter of your home is vital if the insulating method is to work well.