Ventilation for 2 bathrooms/1 roof penetration?

**nola mike** · 01-01-2013, 10:11 PM

I'm installing a bathroom directly adjacent to the existing one. The current vent exhausts air directly into my attic insulation. I'd like to remedy that, as well as install a proper vent in the new bathroom. I'd really like to only need 1 roof penetration. It looks like the way to do this is to have a central fan that exhausts both bathrooms. I would prefer to have a separate fan in each bathroom, and didn't know if there was some type of circular pipe with 2 separate chambers. So that I could have each bathroom have its own piping, but only 1 pipe going through the roof, if that makes any sense. Any other good solutions?

**cacher_chick** · 01-02-2013, 05:12 PM

The fans can be piped together into one outlet. In-line back-draft dampers must be used to prevent each fan from blowing into the opposite bath.

**nola mike** · 01-04-2013, 04:34 PM

Originally Posted by cacher_chick

The fans can be piped together into one outlet. In-line back-draft dampers must be used to prevent each fan from blowing into the opposite bath.

For some reason I thought that wasn't allowed? Do you have a link to the dampers that you're referring to?

**cacher_chick** · 01-04-2013, 04:55 PM

What you might be thinking of is that a kitchen vent hood cannot be connected to other vent systems.
You can get vent dampers at any HVAC supply house.

**djlazar** · 01-04-2013, 07:13 PM

Commercial buildings do this all the time, having one big exhaust fan sucking air out of several bathrooms. The problem would be the extreme cost of this project and the fact that it would be a pain in the ass. If you have an exhaust fan in your attic, it will surely go bad after a few years and you'll be up there changing it out, plus the wiring to it would be a pain. If you put a big exhaust fan on your roof, even more expense and pain the the butt. Do yourself a favor and just put an exhaust fan in each bathroom and vent them separately through their own penetrations, be it through the roof or the soffit. You'll be better off.
Just don't do like you are thinking and connect the ducts. No matter how good you think your backdraft damper is, I can guarantee that you'll smell whatever is going on in the other bathroom.

**nola mike** · 01-05-2013, 06:11 AM

Originally Posted by djlazar

Commercial buildings do this all the time, having one big exhaust fan sucking air out of several bathrooms. The problem would be the extreme cost of this project and the fact that it would be a pain in the ass. If you have an exhaust fan in your attic, it will surely go bad after a few years and you'll be up there changing it out, plus the wiring to it would be a pain. If you put a big exhaust fan on your roof, even more expense and pain the the butt. Do yourself a favor and just put an exhaust fan in each bathroom and vent them separately through their own penetrations, be it through the roof or the soffit. You'll be better off.
Just don't do like you are thinking and connect the ducts. No matter how good you think your backdraft damper is, I can guarantee that you'll smell whatever is going on in the other bathroom.

I wasn't planning on connecting the ducts; what I was hoping for was a circular piece that penetrated the roof. Within that piece would be 2 separate chambers, each of which would be exhausting 1 bath. That way there are 2 separate circuits, but only one roof penetration.