Know Your Roof
Attic Ventilation Terms Explained
Attic ventilation lets outside air in low at the soffit and out high near the ridge, carrying off heat and moisture. When the balance is off, it shows up as ice dams, attic frost, mold and shingles that age early. These guides and terms explain how it works.
Looking for a single word? See the roofing terms glossary, A to Z.
Attic Ventilation guides
Ridge Vent
A ridge vent is the exhaust vent along the peak of the roof. Air comes in low at the soffit, rises as it warms, and leaves through the ridge vent, so it only works if air can get in at the bottom. Together, the two carry heat and moisture out of the attic.
Key terms in this topic
- Air Sealing
- Closing gaps between the living space and the attic so warm, moist air doesn't leak up.
- Attic Condensation
- Moisture that forms on cold surfaces in the attic. Frost on nails in winter is a common sign.
- Attic Insulation
- Material on the attic floor that keeps conditioned air in the house. It works with ventilation, not instead of it.
- Attic Mold
- Mold growth on rafters or deck, often from condensation or a slow leak.
- Attic Ventilation
- The system that moves air through the attic to carry off heat and moisture. Read more about Attic Ventilation
- Balanced Ventilation
- Intake and exhaust that roughly match, so air actually flows through the attic.
- Bathroom Exhaust Duct
- The duct that should carry moist air outdoors. Venting into the attic adds moisture.
- Box Vent
- A low, hooded vent with no moving parts. Also called a static vent.
- Exhaust Vent
- A vent high on the roof, like a ridge vent, that lets warm air out.
- Gable Vent
- A louvered vent in the gable end wall.
- Intake Vent
- A vent low on the roof, usually in the soffit, that lets outside air in.
- Net Free Area
- The real open area of a vent after screens and louvers, measured in square inches. Vents are rated by it.
- Power Attic Vent
- An electric or solar fan that pulls air out. It can draw air up from the house if the attic lacks intake.
- Turbine Vent
- A wind-spun vent that pulls air out. Often called a whirlybird.
- Vapor Retarder
- A layer that slows moisture moving from the living space into the attic.
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