Test and clean the bathroom exhaust fans
Annual · typically June
Why it matters
Every shower puts about a pint of water into the air, and the little fan in the ceiling is the only exit. Even in your moderate climate, a bathroom generates its own weather twice a day — the fan is what keeps that weather from becoming the wall's problem.
The failure that matters most is invisible from the bathroom: where the duct goes. A correct install exits through the roof or an exterior wall. A lazy one dumps into the attic — pumping a pint of steam per shower into cold framing and insulation. That single shortcut causes attic mold and sheathing rot that costs four figures to unwind.
What skipping it costs
$400–$6,000
The bathroom fan is the only machine standing between a daily steam bath and your paint, drywall, and window trim. A dead or furred-up fan means every shower's moisture soaks into the room — peeling paint and specked ceilings first, rotted trim and real mold remediation later. And a fan that vents into the attic instead of outside is quietly running a mold farm above your bedroom.
Two ways to get it done
Do it yourself
You'll need: Step stool, Vacuum with brush attachment, Square of toilet paper (the test instrument), Warm soapy water for the cover.
- The suction test: fan on, hold a single square of toilet paper flat against the grille. A healthy fan pins it there hands-free. If it flutters and falls, the fan or its duct is failing.
- Clean the cover: most pop down by squeezing two spring clips. Wash it in the sink — the felted lint on it is throttling airflow all by itself.
- Vacuum the fan: with the cover off, brush-vacuum the blades and housing. (Flip the breaker if you'll be poking anything more than a vacuum in there.)
- Trace the duct: from the attic, follow the fan's duct with your eyes. It should leave the building through a hooded exit. A duct ending at the soffit, at nothing, or "near" a vent is the finding of the year — that's your fix.
- Retest with the paper square. Still weak with a clean fan? The duct run or its exit damper is blocked — birds' nests and stuck flappers at the wall/roof cap are the usual suspects.
- Habit: run the fan during every shower and 15–20 minutes after. A $20 countdown timer switch makes the after-run automatic and is the best small upgrade in this room.
Hire it out
$90–$180National fair range — local labor moves this number.
An electrician or handyman visit runs $90–$180 — the right call for a dead motor (replacement fans install $150–$400 all-in), a clogged duct run, or rerouting an attic-dumping duct to a proper roof or wall cap ($200–$500, and worth every dollar given what it prevents).
Sizing, if you're replacing anyway: about 1 CFM per square foot of bathroom, so a 5×8 bath wants a 40–50 CFM fan minimum, and quiet ones (under 1.0 sone) cost only a little more and get used far more. The upsell to walk past is anything that starts at one weak fan and ends at a whole-home ventilation redesign.
Ask the tech
- Where does this fan's duct actually terminate — outside through the roof or wall, or somewhere in the attic?
- What's the fan's CFM, and is it enough for this bathroom's size?
- Is there a damper flap at the exit, and does it move free?
Red flags you're being upsold
- A whole-house ventilation system pitch out of a $150 fan visit. Fixing one weak bathroom fan doesn't require re-engineering the house.
- Mold-remediation framing for an ordinary steamy bathroom with dingy grout. A working fan and a repaint with the right primer is a few hundred dollars; 'remediation' is a few thousand.
- A fan replacement quoted without checking whether the duct is just clogged with a decade of lint — the fan's usually fine; its pipe is furred shut.
The call
DIY the test and the cleaning — it's toilet paper and a vacuum. Hire it only if the duct itself is clogged or the fan's genuinely dead, and never let a steamy bathroom get upsold into 'remediation.'