Replaced two bathroom fans in our Vaughan home this spring and learned more than I expected about exhaust fan sizing. The original fans were 50 CFM — technically code minimum — but visibly struggled to clear steam from our 120 sq ft master ensuite.
What we replaced them with:
- Master ensuite (120 sq ft, tiled steam shower): Panasonic WhisperCeiling FV-20VQ3 at 190 CFM — $340
- Main bath (55 sq ft): Broan-NuTone 80 CFM — $85
Installation notes:
- Existing duct was 4-inch flex — upgraded master ensuite to 6-inch rigid metal (contractor ran new duct)
- Added roof cap with proper spring-loaded damper (old one was stuck open all winter — massive heat loss)
- Both fans now on Lutron humidity sensors — auto-run when humidity exceeds 60%, auto-off 20 min after
Labour:
- Master bath (new duct, roof penetration): $485
- Main bath (replacement only, existing duct): $175
Results:
Master ensuite clears mirror fog in under 4 minutes now vs 20+ minutes with the 50 CFM fan. Humidity-sensing switch means it runs without us having to think about it.
Key lesson: size for the actual room. The 1 CFM per sq ft rule is the minimum — for steam showers, go 1.5x.