Homeowner Tips
Roof Ventilation Mistakes That Are Quietly Cooking Your Shingles
Poor attic ventilation shortens shingle life and raises cooling bills. Here are the ventilation mistakes we find most often on Panhandle and New Mexico roofs.
By Taylor Smith · · 5 min read
We pull off a lot of roofs that failed years early, and ventilation is the culprit far more often than the shingle brand. A 160-degree attic bakes the asphalt from underneath, where no warranty covers it. Here's what we find over and over.
Mistake 1: Exhaust without intake
Ridge vents and turbines can only move the air that gets in. If soffit intake is blocked by insulation — extremely common after an attic top-up — the exhaust vent pulls conditioned air out of the house instead. You want roughly balanced intake and exhaust, with intake never the smaller of the two.
Mistake 2: Mixing exhaust types on one attic space
A ridge vent plus box vents plus a powered fan on the same attic doesn't add up to better airflow. It short-circuits: the nearest opening becomes the intake for the fan and the far end of the attic stops moving air entirely. Pick one exhaust system per attic space.
Mistake 3: Venting bath fans into the attic
Still surprisingly common. Warm humid air hits cold decking, condenses, and shows up as "a roof leak" that appears only in winter. Every exhaust fan needs a dedicated duct to a roof or wall termination.
Mistake 4: Undersized net free area
The rule of thumb is 1 square foot of net free ventilating area per 150 square feet of attic floor, or 1:300 with a proper vapor barrier and balanced placement. Note it's net free area, not vent size — screens and louvers cut usable opening by half or more, and plenty of installs never do the math.
Mistake 5: Sealing the attic halfway
If you're converting to an unvented, conditioned attic with spray foam, it has to be done completely and correctly. A half-sealed attic with some vents still open is the worst of both approaches — you get moisture problems without the efficiency gain.
Why it's worth fixing at replacement time
Correcting ventilation during a re-roof costs a fraction of doing it later, because the crew is already up there with the deck exposed. It's the highest-return line item on most estimates and the one homeowners cut first. Don't.
