Bathroom fan size
Shawnnixon1
| Posted in General Questions on
My bathroom size is 10.3×10.3 with 8 foot ceiling. Current have 50cfm fan which is almost useless and loud. I have a stand up shower, toilet and freestanding tub (barely use).
My exhaust fan duct goes to a soffit in the roof. The distance is about 6 feet or so.
how much CFM fan do I need?
Current duct size is 3”. Should I change to 4 or 6”?
Bathroom fan should I get 110cfm? Is 150 overkill?
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Replies
The IRC requires 50 cfm intermittent or 20 cfm continuous for bathrooms, regardless of size.
I recently installed a 110 cfm fan in my bathroom, which is a little smaller than yours, and it clears the air quickly. It's a Panasonic Whisper series and it's nearly silent. I used (and recommend) rigid 4" ducting with as few turns as possible.
Here's how I recommend venting, when possible: https://www.finehomebuilding.com/2018/03/01/bath-fan-venting-cold-climates