What does a soffit vent do on a house, and how can you tell if yours work?
Short answer. A soffit vent is an opening in the underside of the roof overhang that lets outside air into the attic, where it rises and leaves through vents near the ridge. They are working if you can see daylight or a clear baffle channel at the eaves from inside the attic, and the vents are not painted over, crushed or buried in insulation.
What they look like
- Perforated panels: vinyl or aluminum soffit with rows of small holes, on every panel or only some of them.
- Continuous strip vents: a long, narrow louvered strip, usually 2 or 3 inches wide, running down the middle of a wood soffit.
- Individual rectangular vents: louvered metal vents spaced along a wood soffit, often 16 inches long and 4 to 8 inches wide.
- Round plug vents: small circles, often 2 to 4 inches across, in narrow soffits or frieze boards.
A ten minute check
- Outside, look for vents painted over, missing louvers, or panels that have dropped out of their channels.
- In the attic on a sunny day, switch off your flashlight at the eave end of a few rafter bays and look for daylight or a clear baffle path.
- Look for insulation packed against the underside of the roof deck over the walls, which means the vents behind it are blocked.
- Confirm the attic has high exhaust. Soffit vents need a ridge vent or vents near the peak to pull air through them.
What they do for the roof
In Georgia summers, airflow from soffit to ridge carries heat off the underside of the deck, which helps shingles last and eases the load on an attic air handler. In winter it carries away household moisture before it condenses on the cold deck. Many shingle warranties assume balanced intake and exhaust. If your soffits are solid with no vents at all, intake can usually be added by cutting in vents or swapping panels. See roof ventilation basics.