How do you tell if a roof vent is clogged?
Short answer. You can tell a roof vent is clogged when you see debris, nests, or pollen packed in its screen from the roof or ground, when no daylight shows through it from inside the attic, or when the attic stays unusually hot and humid with signs of condensation. Many clogs are actually on the intake side, where insulation or paint blocks the soffit vents.
Signs from inside the attic
- No daylight: on a sunny day, you should see light through a ridge vent slot, box vent openings, and soffit vents at the eaves.
- Stuffy, hot air: an attic that feels stagnant and stays hot long after sunset.
- Moisture: condensation, frost, mildew, or rusty nail tips on the underside of the decking.
- Insulation at the eaves: packed tight against the roof deck with no baffle.
Signs from outside
- Leaves, pine needles, or a yellow pollen mat around box vents and on ridge vent filters.
- Bird or wasp nests in gable vents, turbines, or soffit openings.
- Soffit perforations filled with paint or cobwebs.
- A turbine that does not spin in a breeze.
- Roof caps for dryer or bath vents with lint or debris at the flap.
Simple tests
- Tissue test: hold a tissue or smoke source near a soffit vent on a warm afternoon. Air should be drawn in.
- Temperature and humidity: a small logger in the attic shows whether it cools off in the evening and how humid it gets compared with outdoors.
- Look at the ridge: with binoculars, check whether the ridge vent filter looks matted.
Clearing a clog
Brush or vacuum soffit screens, remove inactive nests, pull insulation back and install baffles, and clean dryer caps. Leave steep roof work to a professional, and do not pressure wash vents, which can push water into the attic. See the Georgia roof maintenance checklist and roof ventilation basics.