Two Bathroom Fans One Duct

I m adding bathroom fans to two back to back bathrooms on a single story house.

Two bathroom fans one duct.

Thanks for any info mike. I just installed two panasonic bath fans in two adjacent rooms and joined them together in the attic it works fine with no backdraft from one fan to the other. One in line centrifugal fan can be mounted in the attic to exhaust the moisture from two bathrooms. The classic example occurs in multifamily units if one tenant is a smoker the tenant next door can smell tobacco smoke that enters the bathroom through the exhaust fan.

Rather than two cheap axial fans into one duct outlet how about two ducts into a more powerful centrifugal fan which is a bit more expensive but has a lot more oomph. Each fan vents separately out the roof. Was replacing bathroom fan 1 and while it was disconnected from its duct pipe the fan in the bathroom 2 was on and. You should not put more than one fan into a common duct each fan should have its own duct run to atmosphere.

Can they share one t top going out of the roof. Afaik if the fans you installed have built in dampers then you can wye them together and use one outlet without a problem. The 2 fans have their own ducts but just before they vent out the roof their duct pipes are attached to a common duct upside down y which means they vent out the same hole in. If you try to combine them into a common duct it will bring with it a number of problems including an unbalanced system with positive negative air pressures which play havoc with the fan motors and could cause motor failure.

I vote to keep the ducts separate. I felt air coming from bathroom 2 s fan down through the metal duct pipe for venting bathroom 1. Each bathroom has its own exhaust fan.