Climate + Building Science Guide
Attic ventilation matters more than most homeowners realize, and it’s the thing most installers do incorrectly. A roof with great shingles and bad ventilation will fail 5–10 years early. Understanding the rules takes 10 minutes.
Attic ventilation works by air movement. Cold outside air enters at the soffits (the underside of the eaves), warms as it rises through the attic, and exits at the ridge (the peak of the roof). For this to work, intake area must roughly equal exhaust area. A ridge vent with insufficient soffit intake doesn’t ventilate — air can’t enter, so air can’t exit. Most attics in NE are intake-starved.
Code specifies a minimum net free area (NFA) of vent. Without a vapor barrier in the ceiling below: 1 sq ft of vent per 150 sq ft of attic floor. With a vapor barrier: 1:300. Half should be at the intake (soffits), half at exhaust (ridge). ‘Net free area’ is the actual open area of the vent — not the gross size of the screen or grill; a louvered vent with screen has maybe 60% NFA.
Common misconception: ventilation is about winter ice dams. Actually, summer matters more for shingle life. Without adequate ventilation, an attic in NE summer can reach 140°F. That heat cooks the shingles from underneath — accelerating granule loss and asphalt aging. A properly ventilated attic stays within 10–15°F of outside temperature. Shingles last 5–10 years longer in a properly ventilated assembly.
Power fan vents (electric attic fans) seem like a solution but often short-circuit the natural airflow — drawing conditioned air UP through the ceiling from inside the home, increasing cooling load. Most building scientists recommend against them. Gable-end louvered vents work but conflict with ridge vents — air enters one gable, exits the other, never sweeping the deck. The right combination is soffit intake + ridge exhaust, full stop.
Go in your attic. Look at the soffits — can you see daylight through them? If yes, intake is probably adequate. Look at the ridge — is there a continuous vent strip? If yes, exhaust is present. Measure: a 2,000 sq ft attic with vapor barrier needs about 6.7 sq ft of NFA total — 3.3 sq ft intake, 3.3 sq ft exhaust. Compare to what you see. Most older NE homes have 30–60% of required NFA.
Adding soffit vents to an existing soffit: $200–$800. Cutting in a continuous ridge vent during a re-roof: $400–$900 incremental cost. Most ventilation fixes are inexpensive and high-return. Schedule with the next roof replacement, or as a standalone project before then if your attic is clearly under-ventilated.
Need help on this in person?
We do this work across CT, ME, MA, NH, RI, and VT. Photo-documented assessment, written quote, lifetime workmanship warranty.
Next step
Photo-documented assessment. Itemized quote. We’ll tell you if repair makes more sense than replacement.