What are roof ventilation intake vents, and which type is best?
Short answer. Intake vents are the low openings, usually in the soffit under the eaves, that let outside air into the attic so exhaust vents near the ridge have something to pull. Continuous soffit vents or fully vented soffit panels give the most even intake; where there is no soffit, edge intake vents at the bottom of the roof deck or fascia vents can do the job.
Types of intake
- Continuous strip soffit vent: a narrow aluminum or vinyl strip running the length of the soffit, feeding every rafter bay evenly.
- Vented soffit panels: perforated vinyl or aluminum panels. Only as good as the opening behind them; over old wood soffit, holes must be cut.
- Rectangular undereave vents: individual louvered vents, commonly 16 by 4 to 16 by 8 inches, spaced along the soffit. Their net free area is well below their face size.
- Round plug vents: small circular vents set into soffit or frieze blocks. Low capacity, so many are needed.
- Edge intake vents: installed at the lowest part of the roof deck under the first shingle courses, for homes without soffits.
- Fascia vents: slots behind the gutter board on certain eave designs.
Why intake is the bottleneck
Exhaust gets the attention because it is on the roof, but intake is the part that most often fails. Insulation blown into the eaves, painted over vents and solid wood behind vented vinyl all choke the system. Without intake, exhaust vents pull air from the house.
How much
Aim for intake at least equal to exhaust, about half of the total required net free area, spread along the eaves on all sides.
See roof ventilation basics, and gutters, sizing and guards for how gutters and fascia interact with intake.