by Paul Scelsi
It Affects Indoor Air Quality, Energy Use, and Roof Life
Most homeowners rarely think about airflow through their attic. But balanced attic ventilation can provide significant indoor air quality, energy usage, and roof longevity benefits.
Attic ventilation is a combination of intake air (vents installed in the soffit, overhang, or low on the roof) and exhaust air (vents installed at or near the peak of the roof or the gable end of the house). When balanced 50% intake and 50% exhaust, ventilation can effectively fight heat, moisture, and ice dams.
During the warmer months, radiant heat from the sun bakes the roof, where temperatures can reach 180°. Some of that heat is transferred into the attic and can radiate into the living space, making it uncomfortable and causing air conditioners to run longer. Homeowners reported 20% energy savings when the attic ventilation was corrected. Heat buildup can contribute to premature aging of the roof shingles–up to 24%.
We generate 2 to 4 gallons of water vapor daily while cooking, cleaning, doing laundry, showering, and breathing. During the colder months, this water vapor is attracted to a cooler, dryer place–the attic. If it’s not vented out, it can condense as frost or water droplets, causing mold, mildew, or wood rot. These can compromise the attic insulation and affect indoor air quality.
Another winter concern is ice dams, which trap snow melt on the roof and trigger damage to the gutter, fascia, the roof, and the house interior. Balanced ventilation helps keep the attic temperature close to the outdoor temperature so that the snow melts more uniformly, minimizing ice dam formation.
WHAT YOU CAN DO TODAY
Look in your attic (or ask a roofing pro) to check if the insulation is mistakenly blocking the intake vents. Make sure the bath fan ductwork exits the roof or gable side of your house to a dedicated bath vent. You don’t want that moisture overwhelming the ventilation system. Most importantly, do you have 50% intake and 50% exhaust for the size of your attic? There are online tools to help you calculate this, including gibraltarbuildingproducts.com and the AirVent YouTube channel.
