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Insulation and air sealing

If your home is properly insulated and air-sealed it will be more comfortable and use less energy. That means lower heating and cooling costs and less environmental impact. If your home is older, it may not have enough insulation and be prone to air leaks.


Insulation slows the flow of heat into or out of your home, making it easier to keep your home warm in the winter and cool in the summer, and reduce noise from outside. The measure of how well insulation material resists heat transfer is called its R-value. The higher the R-value of a product, the better the product insulates. The measure varies for different materials, so when comparing products, be sure to specify the R-value instead of thickness.

Loose fill insulation

  • usually made of cellulose, or glass fibre;
  • relatively low cost, but the R-value per inch is also lower, so you will need more insulation to reach the same R-value as other kinds of insulation;
  • typically used in areas where there is a lot of space and high R-values are needed, such as attics; air flows through this material easily, so dedicated air sealing is needed before you add the insulation;
  • usually installed with a blower, but can also be poured out of the bag.

Batt insulation

  • available in glass fibre or mineral wool, pre-cut to standard sizes and thicknesses;
  • can be used in horizontal or vertical spaces (for example, attics or walls);
  • R-value per inch is similar to or slightly higher than loose fill insulation
  • typically used between framing members (joists or studs) of a wall, in an area such as a basement;
  • provides minimal resistance to air flow, so dedicated air sealing is required.

Rigid or semi-rigid insulation

  • available in either expanded (EPS) or extruded (XPS) polystyrene, polyisocyanurate (polyiso), or mineral wool, and comes in standard sizes and thicknesses;
  • higher R-value per inch than batt or loose fill insulation types;
  • can be applied to the interior or exterior of a home, but is limited on below grade or foundation applications;
  • rigid insulation is most commonly applied to the exterior walls of a home;
  • when applied properly, acts as continuous insulation and may provide adequate air sealing when used in conjunction with sealants or tapes.

Spray foam

  • available in medium density (2 lbs/ft3) through select insulation contractors;
  • can be applied to the inside or outside of a home, including below grade or foundation applications;
  • highest R-value per inch;
  • has air sealing properties that allow it to act as an air or vapour barrier when installed to a minimum thickness of 2 inches;
  • convenient for installation in tight or difficult spaces;
  • one-component foams or foam kits that are sold through building supply centres are not the same as medium density polyurethane foam.

Air sealing

Air leakage can make a room uncomfortable (for example, drafty windows and doors), increase energy costs, and can damage your home. Air leaks most commonly occur at windows and doors, basement rim joists, and electrical or plumbing holes through the wall or in the attic. Air sealing will reduce air flow into or out of your home.

Detect air leaks by clipping a light tissue onto a coat hanger. If the tissue flutters when held against a closed window or door, or in front of an electrical outlet, there is an air leak.

While drafts are obvious and make you uncomfortable, leakage into the wall or attic space can damage your home. In the winter, warm, moist air flows through these holes and comes into contact with cold surfaces, which causes condensation. Reducing the flow of air slows down this process, protecting your home.

Air sealing can be done at any time, but it is often cost-effective to do this work while the walls or attic are being insulated. Sealing your home may change the amount of moisture (humidity) in your home. Read more about managing humidity.


  • draft-proofs your home by sealing the gaps and cracks with weatherstripping;
  • available in a wide range of material types, shapes, and colours suitable to your existing window and/or door system such as:
    • window and door gaskets;
    • weatherstrips and caulking;
    • door sweeps/bottoms;
    • door jamb strips and thresholds.

Window insulating film

  • clear plastic film that can be applied to your windows or doors to reduce drafts and insulate;
  • applied to the window or door frame and is designed to trap a pocket of air between the glass and film, acting like a temporary extra pane of glass;
  • reduces frost and condensation by insulating and sealing the window or door;
  • easy to install and remove, and it shrinks tight for a transparent, wrinkle-free fit;
  • best to install in late fall or early winter.