Why is my ridge vent not working?
Short answer. The most common reasons a ridge vent does not work are that the slot under it was never cut or was cut too narrow, the soffit intake is blocked by insulation or paint, or another exhaust vent such as a gable vent, box vent or power fan is short circuiting it. Less often the filter is clogged or the vent body was crushed by overdriven nails.
Check in this order
- Is there a slot? From the attic on a sunny day, look for daylight along the peak. Solid wood means no slot was cut.
- Is the slot full length and the right width? Short or narrow cuts limit airflow.
- Is intake open? Look for daylight and baffles at the eaves. Insulation packed against the deck blocks intake.
- Are other exhaust vents competing? Gable vents, box vents, turbines or a power fan in the same attic let the ridge vent pull from them instead of the eaves.
- Is the vent crushed? A wavy ridge line suggests overdriven nails.
- Is the filter clogged? Uncommon, but pollen, dust and paint overspray can collect.
Symptoms
- The attic stays hot well into the evening.
- Staining and rusty nails low on the deck near the eaves.
- Frost on nail tips after cold nights.
Fixes
Cutting a missing slot means removing and reinstalling the cap shingles, a job best done carefully or during a replacement. Opening intake can often be done from the attic with baffles. Closing gable vents from the inside is simple. If a power fan competes, disconnect it and plan to deck over its opening. Read ridge vent vs box vents and roof ventilation basics.