Poor attic ventilation in the uppermost part of your home can cause a lot of issues, but most commonly the one’s below. The three parameters for attic condensation in cold climates are – interior house humidity, ceiling airtightness and pressures, and attic ventilation.
During the winter, moist air can collect in an attic that is not properly ventilated. During the summer, hot and humid air can also build up in the attic, putting stress on your roof. High attic humidity usually shows up as dampness or frost on the underside of the roof sheathing. Moisture can also lead to mildew or warping, and mold can start grow, leading to major structural issues. If heat rises into the attic during the winter, it can cause snow to melt and refreeze as ice (ICE DAMMING), which can lead to leaks and further damage!
Here are the four most common reasons to explain the practice of venting attics:
- To reduce the chance of moisture build-up in the attic or condensation on the underside of the roof sheathing.
- To make roofing shingles last longer.
- To lower cooling bills during the summer.
- To reduce the chance of ice dams.
Natural airflow occurs by drawing in the air from outside, pushing it up and out through the vent at the top of the house. This is called passive ventilation.
- Passive ventilation relies on the differences of air pressure from the outside and the inside of your attic. Cooler air is heavier and denser; is pulled into the attic from the soffit, where it warms up and becomes lighter and less dense, and then escapes through the Ridge vent in the gable or attic fans. This pressure creates a vacuum, drawing in the cold air to replace the hot air that has been lost through the gable. However, if you do not have eaves or if you have soffits, ventilation can be a challenge.