One bathroom fan or two?
I have an existing dwelling with two bathrooms on the upper level. These bathrooms share a wall, and the previous owner installed a single fan in each that exhausts into the attic. I know how that can lead to moisture problems in the attic, and I want to vent the bathrooms out the roof. Is it preferable to install a single, remotely located exhaust fan with an inlet duct in each bathroom and a single exhaust through the roof, or to duct each of the two existing fans to discharge separately?
Ted Olmert, Burlington county, NJ
Editorial adviser Mike Guertin replies: Either option would work fine. You might choose a remote fan if you have a tight house and plan to use the fan for continuous ventilation. Also, remote fans can be quieter than individual fans. Finally, with one remote fan, there would be only one exhaust hood on the roof, which is both easier to install than two hoods and would reduce the number of roof penetrations.
On the other hand, separate fans draw air only from the bathroom that requires ventilation (although efi.org offers a damper to prevent this problem with remote fans connected to two bathrooms). In your case, keeping the existing fans might mean less work and less expense since the only thing to do is install new exhaust ports through the roof. Going with a single fan would require you to remove the existing fans, patch and repaint the ceilings, and add new inlet grates. Of course, if the current fans aren’t high quality, they may not work well or may be noisy, in which case you may consider buying and installing new fans.