[gthomson]

So they could put one of these on each side to keep one side from going to the other?
4" Backdraft Damper, Balancing Barometric Backdraft Butterfly Damper Draft Stopper Backflow Preventer (4" / 100mm) - - Amazon.com

I had two bathroom fans going through the roof, but re-routed them out the side of the house instead before I had the roof replaced 5 or 6 years ago. But I just kept them separate, and wanted to get rid of both vents out the roof. I like less holes in the roof, and also wanted fewer things on the roof so it was easier to do solar without having to work around them.

Cutting through that stucco on the side wall was fun

 

[gthomson]

I don't know if this makes sense for you - I only share in case it triggers any ideas on how to do things.
And the bathroom vents I did to the side wall might not be to code - I'm not sure what code is on that.

But this is what I did...

I wanted the bathroom vents and general vents off the roof.
So on the roof re-do, I went with ridge vents on the roof.
And I moved the bathroom vents to the left side of the house.

I used these vents on the outside wall for the bathroom vents going out the side.

HVACQuick - Seiho SBP and SFBP Series Aluminum Dryer Vents with Backdraft Flapper and Tail Piece

Is it the right way to do it - I don't know.
Is it to code, I don't know.
But it's what I did.
I wanted fewer holes in the roof, and wanted fewer things on the roof for the future solar panels to have to work around.
I'm a little OCD on that side of things - when the solar panels are all crazy having to work around the various vents, that drives me batty.

So, it's what I did - comments welcome on what I screwed up on in doing it this way

Roof with vents before -

New roof after with vents moved -

Bathroom vents out the side -