Stay warm with 4 basement insulation techniques

A well-insulated basement is key to a comfortable home. Follow these tips for a space cozy as can be.

Although they're mostly hidden from view and seem safely tucked underground, foundations and basement walls take a lot of abuse from our harsh Canadian climate. Factor in the moisture generated by everyday living inside and you'll realize how important a well-insulated basement is to a comfortable home.

Thankfully, there are many techniques for insulating basement interiors.

When it comes to insulating a home, the most important concept is R-value.

R-value is an industry standard indicating an insulating product’s strength – the higher the number, the better it is at keeping hot and cold temperatures separated. And just as you can put a sweater under a heavy winter coat to dress more warmly, you can increase a basement wall’s insulation strength by layering R-valued building materials.

Many insulating products are firm or rigid while others are soft and pliable "batt" material. There are also insulating foam sprays, which come out of a can as liquid, expand quickly and harden as they dry.

Several years ago Canadian researchers studied home basement insulation methods and costs in several cities – Toronto, Ottawa, Halifax, Edmonton and Victoria – and determined best insulated basements had the same things in common: floor-to-ceiling insulation with an R-20 value. A U.S. study suggests increasing a basement’s insulation to R-20 is worth it. Homes with basement insulation that notched R-20 saved owners up to $390 per year in electricity costs.

What are the best ways to go? Be sure to:

Most commonly, a plastic polyurethane sheet is attached at ground level and draped right down the wall, about a foot into the room. Studs are placed on top, insulating to full wall height. Then a vapour barrier is added on the inside, joining the two sheets from the bottom up to the top, so that it forms a “J” shape. It’s important to ensure that there is no barrier on the part of the wall above ground level on the cold side behind the insulation, so that moisture can escape. The vapour barrier on the warm indoor side should cover the full wall.

These come in boards or sheets. You should start by calculating how much you should need. Be sure to consider not only an extra 10 to 15 per cent for mistakes and odd cuts, but also enough material to cover the wall that may extend above the ceiling and into floor joists. Use the right type of adhesive for the product and use it liberally to ensure proper mounting.

Once the rigid board is mounted properly, use spray foam to fill air gaps. Ideally the spray will entirely fill a cavity, creating a tight seal against moisture or air transfer. Once you’re done with the spray, use insulating tape to seal all seams, not only between insulating products but also where they meet other building materials, such as joists.

Fibreglass batt insulation can be used to boost R-value. However, since the batt material can wick moisture, make sure there’s a vapour barrier in place,such as a polyethylene sheet between the batt and concrete.