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Bathroom ventilation duct length

1848 Views 1 Reply 2 Participants Last post by  Gary in WA
Hi all,

I'm replacing two bathroom fans. Both have runs about 25ft to the gable wall. I'd prefer to not run them vertical through the roof if I can avoid this. Accessing side wall where soffit vents are is pretty much impossible d/t cramped space/roofing nails protruding.

Is a 20ft horizontal run too far? (80cfm and 110cfm fans)

The roof does have some vents at the top. They'd be about 10 foot run, but they aren't termination vents. Previous homeowner vented to these with 3" PVC, ending with a 90deg bend facing toward said vent. Could I vent through these or is that frowned upon?

Thanks for any advice
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Usually on the box instructions... or;

PS. moved you to HVAC.
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