Attic ventilation
Attic ventilation: a roof that breathes, without condensation
Blocked soffits, condensation, ice dams? We install baffles, vent the bathroom fan, range hood and dryer outside, and restore airflow under the roof deck.
The path of the air, from soffit to ridge
- Cold outside air comes in through the soffits, under the roof overhang.
- It passes over the top plate, through the space the baffle keeps open.
- It runs up along the roof deck, picking up moisture on the way.
- It leaves at the top, near the ridge.
As long as that current flows, the roof wood stays dry. Block the way in at the soffit, and everything else stops.
What cuts it off
A soffit gets blocked more easily than you’d think: wood closing off the air intake, or insulation blown right to the edge of the roof, with no baffle. The soffit is still there, outside. It just doesn’t do anything anymore.
The other problem is moisture sent up there without anyone knowing. A bathroom fan, range hood or dryer whose duct ends in the attic blows steam-laden air into it, and warm air rising through ceiling leaks adds more.
What you notice when the air stops moving
Outside, in winter: thick icicles along the roof edge, an ice dam in the eavestrough. Heat escaping from below melts the snow, and the water refreezes at the edge.
Inside: condensation on the roof deck, then stains on the wood, a musty smell upstairs. If mold is already there, see our page on attic mold removal.
From below
The soffit lets the air in
Cold air comes in through the soffit and passes over the insulation, thanks to the baffle. As long as it flows, the roof wood stays dry.
What we install, and what we vent outside
The wood blocking the soffits, removed. Then a baffle at every soffit: set against the roof deck, above the top plate, it keeps a passage open for air even when insulation is blown right to the edge.
Ducts for the bathroom fan, range hood and dryer, vented outside. The steam leaves the house instead of ending up on the roof wood.
Ceiling air leaks, sealed, so warm air stays downstairs, where you’re paying to heat it.
Then the insulation, blown to R‑51 minimum without touching the soffits: that’s on our attic insulation page.
What stays in place
Ventilation proves itself in winter, with snow on the roof.
The baffles stay under the insulation, at every soffit, keeping the passage open from one season to the next. The ducts end outside. If you ever go up to the attic, look at the roof edge: the insulation stops at the baffle, and the air gets through.
FAQ
The questions we get the most
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- I already have soffits, isn’t that enough?
- Only if air gets through. When insulation covers them from the inside, they’re just for show.
- Why baffles if I’m only adding insulation?
- Because that’s exactly where it gets blocked. A lot of jobs blow insulation right to the roof edge without putting anything over the top plate. At Isolation Cornerstone, a baffle goes in at every soffit before we blow.
- My bathroom fan vents into the attic, is that a big deal?
- Every shower sends its steam onto the roof wood. We vent the duct outside.
- Icicles along the roof edge, is that the ventilation?
- Often it’s both at once: warm air leaking up, and cold air no longer getting in. Isolation Cornerstone fixes both on the same job.
- Is it done at the same time as the insulation?
- Yes, and always first. At Cornerstone, we don’t blow insulation into an attic whose ventilation hasn’t been fixed.
Get your free quote
We look at your soffits, ducts and roof deck, and tell you what’s blocking the air.
Or call us at (438) 544-6512