Are roof vents worth it, and which kinds are worth paying for?
Short answer. Passive roof vents such as ridge, box, and soffit vents are almost always worth it, because they cost little relative to the roof and help protect the decking and shingles from heat and moisture. Powered attic fans are less clearly worth it; they cost more to run and maintain and can pull cooled air out of the house if intake is short.
What you are paying for
Roof vents do not make a house dramatically cheaper to cool when the ceiling is well insulated and sealed. Their real value is protecting the roof assembly: drier decking, fewer moisture problems, less heat stress on shingles, and staying within the ventilation expectations of the shingle warranty.
Value by vent type
- Ridge vent: strong value on gable roofs, especially when added during a replacement.
- Soffit intake: the most overlooked bargain. Adding or unblocking intake often improves airflow more than adding exhaust.
- Box vents: inexpensive and simple, good for hip roofs, but each one is a separate penetration that can crack in hail.
- Turbines: move air well in wind, but bearings wear and squeak, and damaged ones can leak.
- Power and solar fans: helpful in a few situations, but motors and thermostats fail, and without generous intake they can depressurize the attic and draw air from the living space.
When vents are not worth adding
If the attic is already balanced and dry, more vents just add holes. If the home is being converted to a sealed spray foam attic, vents work against the design. And if the roof is near the end of its life, plan ventilation upgrades into the replacement instead of paying to cut new vents into old shingles. For the basics, see roof ventilation basics and how heat and humidity affect roof life.