What kinds of soffit vents go under the eaves, and which work best?
Short answer. Under-eave vents come in four common styles: continuous strip vents, fully perforated soffit panels, individual rectangular undereave vents and small round plug vents. Continuous strips and fully vented panels give the most even intake, while rectangular and round vents work but usually need more units than people expect, because their net free area is much smaller than their face size.
The four styles
- Continuous strip vents: a narrow louvered strip set into a slot along the soffit. Even airflow into every rafter bay, and a clean look.
- Fully vented soffit panels: perforated vinyl or aluminum across the whole soffit. Plenty of area, provided nothing solid sits behind them.
- Rectangular undereave vents: individual louvered vents, commonly 16 inches long and 4 to 8 inches wide, spaced along wood or fiber cement soffits.
- Round plug vents: small circular vents pressed into drilled holes. Low capacity each, so many are needed.
Open eaves
Homes with exposed rafter tails and no enclosed soffit use vented blocks, sometimes called bird blocks or frieze blocks, between rafters at the top of the wall, screened to the code range.
Placement tips
- Spread intake along all eaves rather than concentrating it.
- Do not count soffit over a porch roof that does not connect to the main attic.
- Keep intake away from bath or kitchen exhaust outlets.
- Keep paint out of the louvers.
Face size vs net free area
A rectangular vent's face is its gross area; louvers and screen reduce the net free area to a fraction of that. Use the stamped rating when counting how many you need. Read roof ventilation basics and roof anatomy explained.