Why is it so important to have proper ventilation on your building?
Your ventilation setup extends the life of the entire roof system, especially shingled roofs in warm regions, by minimizing the temperature differential between the attic air and the outside air. This helps prevent condensation, mold, and ice dam formation while simultaneously providing sustainability via efficient energy usage.
Benefits for Warm Regions
In warm regions, during the dog days (and months!) of summer, proper ventilation on your building will help keep the roof cool, ultimately extending the life of the roof. Keeping your roof cool is important, as excess heat causes shingles to curl and deteriorate.
Example (Fig. 1): Without proper ventilation, the left side of the attic is heating up to roughly 140 degrees, causing the roof sheathing to be 170 degrees. Meanwhile, the right side has a solid ventilation setup in place, resulting in the attic being roughly 25 degrees cooler while helping prevent premature shingle deterioration.
Studies conducted by Oak Ridge National Laboratories found that ventilation can reduce the heat gain through the roof assembly up to 45% when compared to an unvented system.
Benefits for Cold Regions
In cold regions/winter months proper ventilation also helps minimize the temperature differential between the attic and the outside air (Fig. 2), thus reducing the risk of moisture buildup which can cause rust and corrosion in metal roofs, insulation damage, and mold/mildew.
One of ventilation’s biggest benefits is preventing freezing/thaw cycles that cause ice dams. There are three keys to preventing ice dams:
Proper insulation: see the U.S. Department of Energy recommended R-values for each region.
Use of ice and water shields
The U.S. Department of Energy has specific recommendations to properly insulate a building based on the climate, type of heating and cooling system, and the part of the building you plan to ventilate.
Proper Ventilation At-A-Glance
Proper ventilation minimizes the temperature differential between the attic and outside air
This prevents freeze/thaw cycles that cause ice dams by bringing in outside air at the eave and exhausting it at the ridge