Bathroom Fan Venting & Exhaust Ducting
I vent bathroom exhaust fans to proper exterior terminations, clearing moisture out of the home instead of into the attic, where it causes condensation and mould.
What I do
- Route fan ducting to exterior wall or roof terminations
- Replace flexible duct with insulated rigid duct
- Seal and insulate runs to cut condensation
- Add or relocate exterior vent caps
- Correct fans that dump into attics or soffits
Common problems I fix
- Fans vented into the attic, soffit, or crawlspace
- Condensation, mould, or staining around the fan
- Long, sagging flex duct that traps moisture
- Missing or blocked exterior vent caps
Good-fit projects
- Bathroom and ensuite renovations
- Older homes with improperly vented fans
- New bathrooms added in a renovation
- Moisture or mould complaints upstairs
A bathroom fan only works if its duct carries the moist air all the way outside. In a lot of homes it does not: the fan vents into the attic, into a soffit, or into a long sagging flex duct that traps water. I route bathroom exhaust to a proper exterior termination so moisture leaves the home.
Where does a bathroom fan need to vent?
A bathroom fan must terminate outside the building, through an exterior wall or the roof with a proper vent cap. Venting into the attic or crawlspace pushes humid air into a cold space where it condenses, soaking insulation and framing and growing mould.
Why fans cause condensation and mould
Three things cause it: uninsulated duct in a cold attic, flexible duct that sags and holds water, and runs that never reach the exterior. I replace sagging flex with insulated rigid duct, keep the run short and sloped, and seal it to an outside termination.
Common in renovations and older homes
Bathroom fans are often added or moved during renovations, and the venting is the part most likely to be done poorly or skipped. Getting the duct routed and terminated correctly while the ceiling is open is far easier than fixing condensation damage later.
Where I provide this service
I serve Squamish, Whistler, Pemberton, and nearby Sea to Sky communities. See service areas.
Related services
Frequently Asked Questions
Can a bathroom fan vent into the attic?
No. A bathroom fan must vent to the outside, not into the attic, soffit, or crawlspace. Venting into the attic dumps humid air into a cold space where it condenses, causing moisture damage and mould. I reroute the duct to a proper exterior termination.
Why does my bathroom fan cause condensation or mould?
Usually the duct is uninsulated, sags and traps water, or never reaches the exterior. Warm humid air hits cold duct or attic surfaces and condenses. I replace sagging flex with insulated rigid duct and run it to an outside termination.