jetty_junkie t1_j9qybin wrote on February 23, 2023 at 10:50 PM

no, you aren't overthinking it. when i was doing my fan i did some reading an apparently 3" duct can olny handle so much air, so when you adapat a larger fan you often get backpressure because its pushing air in faster than it can go out.

as for the changing it the vent it can be super easy or impossible depending on your house and how the vent pipe is routed because 4" vent isn't going to fit in a 2x4 framed wall cavity so if it's a 2nd floor bathroon with attic access thats easy, but if its a 1st floor bathroom that vents through the roof that's a different story

ItCouldaBeenMe t1_j9s79o8 wrote on February 24, 2023 at 4:23 AM

If the bathroom is on an exterior wall and the joists are going perpendicular to it, you could vent out the exterior wall.

rayw1983 OP t1_j9scrhw wrote on February 24, 2023 at 5:14 AM

Thanks for your response, makes me feel better that some back pressure is expected.

I’ve done my bathrooms upstairs which was fairly easy but this time unfortunately it’s the downstairs bathroom. It does vent up through the roof so I unless I open up walls I guess this will have to do.