Bathroom exhaust vent sizing in 2×4 walls
We recently bought a front to back split so there are essentially three levels with our master bedroom and bathroom at top. It turns out the bathroom exhausts for all three bathrooms run into the attic but luckily there doesn’t appear to be much mold. They used flexible duct.
We are replacing all of the old, rattling fans ducts, but we have 2×4 interior walls and a long run for the basement bathroom.
Can we use rectangular metal duct for the vents or do we need to stick to round?
The basement bathroom is on the back exterior of the house so would it be okay to vent there to get a shorter run even though it’s not a gable end?
What are the best covers to put on the exterior of the house to prevent critters from getting into the house?
I greatly appreciate any advice. Thank you.
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Replies
Allysn,
You probably want to start by reading this article: Bathroom Exhaust Fans.
A duct designed to fit between 2x4 studs is called wallstack. You can use 3 1/4" x 10" wallstack to vent a bathroom fan if you have to, as long as you use a minimum number of fittings and keep the duct as short as possible.
The best exterior terminations for your bath exhaust fan are probably the ones made by Seiho. Model RCC-S is sold as a dryer vent, but it should work for a bathroom exhaust duct. It includes a backdraft damper. Here is a link: https://www.seiho.com/product/index6.html.
You don't have to vent your basement bathroom through your attic. Go through the rim joist or an exterior wall, as close to the bathroom as possible.
-- Martin Holladay