When it comes to ventilating your home’s attic, the right amount of air flow and air volume can make a significant difference to the comfort and durability of your home. There are four primary reasons to ventilate, two of which relate to the comfort of your home and all of which can affect its durability. The four reasons for ventilating are:
Reduction of summer time heat in attics: Proper ventilation will improve flow of the sun-heated air and direct it out and away from the attic space, reducing heat that radiates into living areas. For flat roof designs, it is critical to cross ventilate through perimeter vents and unobstructed air movement channels within the roof’s joist cavity. For steep sloped roofs, ventilation is typically achieved through eave and ridge vents with at least 50 percent of the ventilation capacity located high on the roof’s ridge. Your local Building Department and current Building Code will provide specifics regarding Code compliant installations.
Reduction of winter time moist air and condensation in attics: Attic moisture as vapor can condense to water droplets when coming into contact with a cooler surface, and then can drip onto attic insulation, gypsum board ceilings and wood framing causing them to stain or deteriorate. Proper attic ventilation can help to eliminate moisture and discharge stagnant attic air, reducing the potential for condensation.
Ice Dams: An ice dam is a buildup of ice at the edge of a roof, which prevents melting snow water from freely draining off the roof. Roof temperature imbalances cause the dam to form as melting snow flows down the roof but freezes again at the point where the roof is below 32°F. The ice builds up over time as more water collects at the roof edge and freezes again. Then the water above that has not yet reached freezing backs up behind the ice dam.