Thursday, Sep 27, 2012

Winter comfort starts with insulation

The right insulation can save you money, reduce the amount of energy you use and make your home more healthy and comfortable.

You can suspect an insulation problem if your walls or floors are cold to the touch in winter or you have uneven temperatures in different rooms within the house. High heating costs or mold growth may also indicate ineffective insulation.

Insulation effectiveness

Insulation is a critical part of the building envelope system, which includes the roof, walls, windows, doors and foundation of your house. Effective building envelope systems slow the movement of heat and deal with the movement of moisture and air at a reasonable cost. The components of an effective system include: an air barrier; carefully installed insulation; a minimum of thermal bridges to prevent heat escaping; a vapour retarder such as polyethylene sheeting; and some drying potential, which is the ability to release any moisture that gets into the envelope system.

R-values and their metric equivalent, RSI values, are a way of labelling the effectiveness of insulating materials. Basically, the higher the R-value, the more resistance the material has to the movement of heat. But it’s important to note that proper installation also plays a large role in the effectiveness of your insulation.

Attics and basements

The attic is often the most cost-effective place to add insulation. Usually, a contractor blows loose fill into and over top of your ceiling joists. However, batts laid sideways on existing insulation are an easy alternative if you want to do it yourself. The key to effective attic insulation is to ensure the air barrier at the ceiling line is well sealed, to prevent warm, moist air from the house from getting into the cold attic and condensing.

Basement walls are unique because they must handle significant flows of moisture from both inside and outside the house. Basement walls can be insulated from the outside or the inside, and there are advantages and disadvantages to both options. The preferred method is to insulate the wall on the outside with rigid insulation suitable for below-grade installations, such as extruded polystyrene or rigid fibreglass.

If that’s not possible, interior insulation can also be used. Unfortunately, with interior insulation, the basement walls are now at the temperature of the soil or the outside, so any moist air moving through the wall from the inside will condense on the foundation wall. Also, there is usually a moisture barrier against the foundation wall and a vapour retarder on the room side of the insulation. As a result, the wall has poor drying potential. For these reasons, you should never apply interior insulation to a basement wall with moisture problems. You will need to fix the problems before insulating.

If your home is poorly insulated, it pays to upgrade the insulation. It’s important to choose the proper insulation system for your needs, and when in doubt, it’s wise to consult a professional.

To help you learn more about the benefits of insulation and the different types of materials available, Canada Mortgage and Housing Corporation (CMHC) has a free About Your House fact sheet called “Insulating Your House.” To order your copy, visit us online at or call our toll free number: 1-800-668-2642.

Mark Salerno is district manager for the GTA at the Canada Mortgage and Housing Corporation. You can reach him at 416-218-3479 or

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