How do a ridge vent and soffit vents work together, and what if there is no soffit?
Short answer. Soffit vents are the intake and the ridge vent is the exhaust: cooler air enters under the eaves, rises along the underside of the deck and leaves through the ridge, so each one only works if the other is there. A ridge vent with no soffit intake will pull air from the house or from other vents instead; homes without soffits can use edge intake vents installed along the bottom of the roof.
Ridge vent vs soffit vent: not competitors
People sometimes ask which is better, but they do different jobs. Exhaust without intake is like a chimney with the bottom sealed. The ridge vent creates the pull, mostly from warm air rising and wind passing over its external baffle, and the soffit vents supply the replacement air along every rafter bay.
Getting the balance right
- Aim for intake at least equal to exhaust; many installers prefer a little more intake.
- Spread intake along the full length of the eaves, not just a few vents near the corners.
- Put baffles in each rafter bay so insulation does not choke the opening.
- Close off gable vents and remove old box vents near a ridge vent, or the ridge vent may draw from them instead of the soffits.
If your house has no soffit
Many older Georgia ranches and some contemporary designs have tight eaves or none at all. Options include:
- Edge intake vents installed at the bottom of the roof deck under the first shingle courses.
- Fascia vents where the eave construction allows.
- Skipping the ridge vent if no intake is possible, since a ridge vent alone can draw conditioned air and moisture up from the house.
For how much of each you need, see roof ventilation basics; for exhaust choices, ridge vent vs box vents; and for the edge itself, drip edge explained.