Anyone smart enough to know a reasonable solution to this problem?

[Bill Featherstone]

We have a 60's brick ranch house that we are remodeling ... one story with a full basement ... it has 2 small baths that stack on top of each other, both on the back wall of the house ... the exterior wall on the top bath is brick veneer on wood frame and the the exterior wall on the lower bath is 10" concrete block ... now, the issue we have ...

neither bath has an exhaust fan ... I don't want to just exhaust the upper bath into the attic space and going through the brick wall to the outside would be a pain; however, going into the attic and piping to the soffit (we have a fairly wide overhang) seems like a reasonable solution ... but, what about ...

the lower bath? ... the only options I can come up with to vent to the outside is to go through the concrete block exterior wall (ugh!), go into the space between the two floors and then through the brick exterior wall above (not easy either), or lastly ...

go up and through the upstairs bath and tie into the exhaust pipe in the attic (in other words, share the same exit pipe with the upstairs bath) ... this could be done fairly easily since both baths are currently torn down to the studs ... my question is ...

can or should this be done? ... I've never seen it done before ... it's a long way for the exhaust to go up and out from the lower bath to the soffit on the upper floor ...

any ideas or suggestions about how to solve this exhaust challenge? ...

if my idea makes sense, how should I size each of the exhaust fans? again, both baths are small (about 7' x 7').

Thanks in advance, Bill

[Greg Veal]

Bill

I would try to vent the lower bath by running the vent ductwork through the perimeter band sitting on top of the 8" - 10" CMU/Hollow Block foundation wall, even if you must cut through the brick veneer.
I would vent the top bath by running the ducting up and over the single or double plate of the frame wall, between the joists and then out through the soffit. I am assuming some framing standards, because your post doesn't show your location, and framing practices very somewhat all around the country. I would make sure to install the backdraft damper/flap on each fan unit to prevent cold drafts, possibly even insects or other other intrusions.
Lastly, you could take the approach you have laid out in your posts, but sizing and installation of the ducting will be very important. Most fans require either a 3" or 4" round duct connection. If I were doing what you described, I'd run the lower fan duct full size up to and just past the upper fan, using ridgid pipe if at all possible, and as few elbows as possible. Connect the upper duct, angled with the flow of exhaust and increase at least 1" (ie: 2-3'' ducts should increase to at least a 4"). Tape(Alum.Foil) or apply a firerated mastic to the all joints and/or fittings.
Don't forget the Backdraft Dampers on each Fan Unit. If they didn't come with them, take'um back and get fans with dampers.

Just my opinion, hope it's helpful.

[Bill Featherstone]

[quote=gveal]Bill

I would vent the top bath by running the ducting up and over the single or double plate of the frame wall, between the joists and then out through the soffit. I would make sure to install the backdraft damper/flap on each fan unit to prevent cold drafts, possibly even insects or other other intrusions.

Don't forget the Backdraft Dampers on each Fan Unit. If they didn't come with them, take'um back and get fans with dampers.[quote]

Do backdraft dampers ordinarily come with the Broan fans you can buy at Home Depot? Are they just the flappers that open up in the vent at the exit point? What do they look like?

Thanks for your help, Greg.

[Robert M. Delre]

Hmmm...Aren't you worried about condensation and it running back down through the fan? That is if the downstairs bath has a shower. I wouldn't think that the moisture will be able to escape properly being such a long vertical climb. JMO

[Robert M. Delre]

I would ask the local building inspector what the codes are for that. I am sure there is one.