Part of The Complete Guide to HVAC Maintenance
It's mostly a ventilation problem
Attics are supposed to have continuous airflow — cooler air entering low (usually at the soffits, under the roof eaves) and hot air escaping high (at a ridge vent, gable vent, or attic fan). When intake or exhaust is blocked or undersized, heat has nowhere to go and builds up, sometimes reaching well over 100°F even on a mild day.
Common culprits
- Soffit vents blocked by insulation pushed too far into the eaves
- Not enough exhaust ventilation at the roofline for the attic's size
- Bathroom or kitchen exhaust fans venting into the attic instead of outside (this also introduces moisture, which is its own problem)
- Insufficient attic insulation, letting heat from the living space below add to the problem
Why it matters beyond comfort
A hot attic radiates heat into the rooms below, making your AC work harder. It also shortens asphalt shingle lifespan from the underside, and in cold climates, an attic that's too warm relative to the roof surface can contribute to ice dams in winter.
What homeowners can check
Look for visible soffit vents from outside and confirm they aren't painted over or blocked by insulation from inside the attic. Confirm bathroom fans actually vent outside, not just into the attic space. Beyond that, proper ventilation sizing is a calculation based on your attic's square footage, and is worth having a professional assess if the basics check out and it's still a problem.
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