If you have two bathrooms which are close to each other and one of them has an exhaust fan and the second doesn’t, you could wonder if you can connect a new exhaust duct to the one that is already in place. No, you can’t do that. Many times, you’d blow air from one bathroom into the other, and the local construction inspectors wouldn’t let you get away with it.

However, while it is not possible to have two fans with a single vent, it is possible to have one fan and one vent serving two bathrooms. For this configuration, an in-line centrifugal fan positioned in the attic must be used to take air from both bathrooms at the same time.

A grille in each bathroom connects to ducts, which are then connected to a “Y” connector at the ceiling fan by a “Y” connector. A single exhaust pipe leaves the building through the roof. Each bathroom will have a switch installed. This system is also quite quiet. Since the fan is in the attic, you won’t be able to notice it very well. Look for the specific fans at dealers who sell heating and cooling equipment.

Although it will require another hole in the siding or roof, it is cheaper and more expensive to just install a fan in the second bathroom and separate the venting. If you choose to go this way, look for a fan that includes a built-in humidity sensor. A quick increase in humidity, such as after a shower, is detected, and the fan is activated by an automated sensor. Although the fans that come with this update are not inexpensive, they do away with the necessity for a timed switch.