As Fall approaches, it is a good time to consider the importance of proper attic ventilation. Improperly ventilated attics are more vulnerable to Hoar Frost that can grow to become ‘sheets of ice’ during extended periods of extreme cold temperatures; then, during a Calgary Chinook it can literally rain inside of your attic which can destroy your insulation, and cause mold and mildew. An ideally-ventilated attic will have ‘soffit-to-ridge-airflow’. This is achieved by having ventilated soffits at the eaves and vented ridge at the peak of the roof, but do not vent the soffits at the gable-ends… because escaping air from the roof peak would be replaced from the closer soffit vents at the gable ends rather than pulling air into the attic from the eaves. Similarly, it is advisable to close off any ‘other’ venting such as gable-end vents, roof turtle vents, etc.
A properly ventilated attic will allow the home to be warmer during the winter because the ‘super cold’ midnight-to-6:00-AM air can be replaced with warmer morning air surrounding the eaves; also, the house will be cooler in the summer because the ‘super hot’ 1:00 PMto-4:00 PM afternoon heat can be replaced with cooler evening air allowing you to sleep more comfortably at night. Another reason to have ‘soffit-to-ridge’ venting is that during high humidity and sudden cooling temperatures, the snow/ ice accumulation on the roof at the eaves, creates a situation where the roof deck become ‘wet’ under the shingles, as well as the attic underside, because moisture is attracted from the air to anything that is colder than it is. Soffit-to-ridge air flow dries this area faster than static air will, plus when hoar frost accumulates, sublimation can occur (the frost will turn to vapour without becoming liquid first). It is extremely important to have soffit venting, working with ridge venting in ‘open beam’ ceilings in order to cause air flow between the trusses (your insulation will be much more effective, and retain it’s desirable qualities longer). Roof ‘turbines’ placed far apart, and near the roof peak, will also work with vented eaves soffits, because the turbine fins are constructed to keep rain & snow from entering the attic (do not cover them in the winter), and to draw the attic air out, creating the ‘updraft’ that is necessary for eaves-to-ridge attic air flow. Power vents, wind turbines, and ridge venting all work with vented soffits at the eaves to optimize attic conditions. Most roof ‘turtle vents’ do not give satisfactory results! Have a good Fall & Winter, and protect your home.
If you are uncertain whether your attic is vented adequately, consult ‘An Expert’.