What can we do about it?
Basic Building Science Principles are to control the flow of heat, air and moisture in our homes. Cool attics usually result in cool roofs which will prevent the snow melting that creates the ice dams in the first place. This is the first line of defense.
The attic generally becomes the first place that comes to mind when we think of adding insulation. It has relatively easy access and few obstructions that make the attic a favourite starting point for homeowners.
Adding more insulation, however, is only half the battle.
Heat wants to move from any area of warmth to areas of cold. Many people believe that because hot air rises, most heat loss will be through the ceiling. Not necessarily so. Heat moves in any direction, up, down, or sideways – as long as it is moving from a warm spot to a colder one. Warm air that leaks into the attic accounts for substantial heat loss, especially during the winter when our houses operate like a big fat chimney whereby air tends to enter at the lower levels and exit at the upper levels.
Air leaks are usually found at penetrations or discontinuities. The best line of defense is a systematic identification and sealing of as many of the air leakage paths as possible. Comprehensive air leakage control cannot be understated.
Some examples of common air leak areas are electrical outlets, bypasses around chimneys and plumbing stacks that can channel air directly from the basement to the attic, recessed spot lights, gaps under baseboards, pocket doors, exhaust grilles, attic hatches, cold air returns, ducting for fans or heating systems, bulkheads, top plates and any breaches in the air barrier system.
In Building Sciences, it is important to understand too that your house works as a system. Each part is related to all other parts. Any change in one place causes an effect elsewhere. For example, reducing air leakage makes the house more comfortable and protects the envelope from moisture damage, but it will also increase humidity levels in your home, since less water vapour escapes. This may create an increase of condensation on the windows.
If you find your home has more than average winter leaks (all homes are unique from each other) you may want to consider a professional air sealer. Professional air sealing companies often use a depressurizing fan test to identify and measure the air leaks in a house.