A bathroom is an ideal place for mold to take root. It is moist, warm, and can remain in that state for quite a while if there is no ventilation. A bathroom exhaust fan is one of the best ways to keep the humidity in your bathroom at a comfortable level and keep mold at bay. Use it in conjunction with a device that measures humidity and you'll be able to keep your bathroom dry and mold free.
There aren’t many options for routing an exhaust fan to the outside of the house. There are really only three venting options.
Through the Wall
No matter the location of the bathroom, you can vent the exhaust fan through the wall. Ductwork is what will connect the fan to the outside. The location of the bathroom will determine how extensive the ductwork will be. You may be able to configure a short route. However, bathrooms that are further from an exterior wall will usually have a longer, more complex route.
Since the roof doesn’t have to be cut, the chances of this venting method causing a leak is less likely. Gravity helps this because when water hits the side of the house, it will run to the ground. Holes that are cut into the sides of building usually don’t have problems with taking on water.
Directly Through an Exterior Wall
There is a fan that you can purchase that can be vented directly from the bathroom to an exterior wall. While this seems the easiest option, this fan usually requires that a new electrical line be installed. Therefore, this option is the least popular of the three among do-it-yourselfers.
If you are doing a complete bathroom remodel or have to have electrical wiring done anyway, you may want to consider this option. It eliminates the need for routing ductwork through the house and these fans usually dry the bathroom more quickly.
Through the Roof
Depending on the location of the bathroom, it may be easy to vent the exhaust fan through the roof. This involves running ductwork from the fan, usually though an attic, and out through the roof. In order to accomplish this, the roof has to have a hole cut in it. It is because of this that many builders tend to advise against this method. Most professionals believe that the roof should not be cut unnecessarily.
Construction professionals will tell you that they go out of their way to avoid having to cut into a roof. Though flashing and roof boots can be used to prevent the penetration of water, eliminating openings all together is the best defense against intruding moisture. While this is a viable option, it should be used only as a last result and it will require additional maintenance to the roof area to make sure that water is not seeping into the house.
You can now make an informed decision on which way you will vent your bathroom exhaust fan. This decision will probably be easier than choosing the actual fan!