Bath exhaust fan opinion

I have renovated many bathroom myself but would like an opinion from you guys. I have a two story cape house with a full basement. A “doggy dormer” was added in the 80’s for a 2nd floor bath, but no exhaust fan. I am guuting bathroom and I am going to install anew bath fan. My question is have any of you seen the ductwork piped to the basement, then exit the house. The reason I would even consider this is because of the “doogy dormer” and the exhaust grill placement would look like crap. I have a old dryer vent opening in the basement that I could pipe through. My concern is the moisture that might accumulate where the exhaust pipe elbows in the basement to run through the exterior wall.Any opinions welcome.

Is it a full bath? From the standpoint of damage to the structure exhausting a bathroom with a shower poses a much greater potential risk than a powder room.

I any case, one concern in the setup you are discussion is that the longer the run and the more turns the more condensation in the vent pipe. If you have low spots, likely you will eventually get substantial corrosion.

Assuming it was properly pitched, from the standpoint of effective exhaust with a long run and multiple turns one option would be to use a fan with a 6" exhaust, such as the NuTone QTXN line.

But IMO a better solution if you are concerned about the aesthetics would be a vertical exhaust via a roof cap (roof jack):

Isn’t this just a bathroom exhast.
Would it not serve you better to use plastic flex duct.
Less expensive.Easier to route.Will not corrode.Is made for this specific application.


I’d agree it’s not nearly as much an issue as for a dryer vent, but if you are looking for a supportable position, most manufacturers prefer smooth, rigid pipe; see for example pp 6, here:

Minimum standards (and common sense) require that ducting in a residence be at least resistant to fire and the sreading of flame or smoke.

Plastic ducting fails in this respect. If a fire starts in any part of the house near plastic ducting, it might spread very quicly along the route of the ducting.

Whether you decide to route your ducting to the basement and outside or directly through the exterior wall or roof, use ducting that will allow no or minimum fire and smoke spread. Look for the UL 181 listing on your ducting.

(I vote for exhausting through the roof or an exterior wall near the bath, myself.)

Just to clarify the “doogy dormer” looks like a dog house built in to the existing roof. I have not seen venting whether plumbing(pipe) or exhaust(ductwork) penetrate through the side or through the roof of one of these dormers.I was going to use a Continental fan locating it in the basement.It has almost 250 CFM, probably more than double than your normal bath fans

You’ve got plenty of options staying on the same level of the bathroom…

Why send air down through your wall which can cause unnecessary moisture issues and probably Mold build-up if this vent leaks air.

I’ve never seen bathrooms vent to the lower portion of the house. It’s very risky.

Stay on the same level. There are all sorts of options.