The Importance of Proper Attic Ventilation

shutterstock_136347395Many people think that the purpose of attic ventilation is to allow heat that builds up in the attic during hot summer days to escape. That’s true, but it’s only part of the big picture. During winter, attic ventilation is important for allowing moisture that could damage the structure of your roof to escape.

Without proper ventilation, an attic can get incredibly hot during the summer. When the outside temperature reaches 32 degrees C, the temperature at the roof deck can hit 77 degrees C (170 degrees F). At the attic floor, the temperature can be as high as 60 degrees C (140 degrees F). The heat from the attic can make the living areas of your home unbearably hot. An improperly or poorly ventilated attic will also retain much of its heat through the night. Extreme heat in a poorly ventilated roof can cause shingles to curl and deteriorate prematurely.

Properly installed attic vents act like chimneys. Hot air from the attic rises and escapes through the vents and is replaced by cooler air from outside. Ironically, the more attic insulation you have, the more important it is to have proper attic ventilation. A thick layer of insulation absorbs and retails heat.

In colder climates like Calgary, attic ventilation is crucial for preventing the buildup of moisture in the attic. Warm air laden with moisture from cooking, laundry, and bathing inevitably makes its way from the living areas of the home into the attic in a process called vapour diffusion. Water vapour can make its way through drywall and gaps around ceiling mounted light fixtures. Even vapour barriers cannot completely stop the process.

When moist warm air hits cooler roof sheathing, joists, and rafters, water can condense. Not only can the condensed water cause wood rot and mould, it can drip down onto insulation, compressing it and reducing its effectiveness.

During winter, proper ventilation allows cool outside air to flow along the underside of the roof sheathing and replace warm moist air with cooler dry air. The result is a cool, dry attic. A properly ventilated attic is also important for preventing the formation of ice dams.

For all of your roofing installations, repairs, and inspections in Calgary and area, contact The Roof Hospital.

By Eric Gilbert

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