Having a bathroom in the basement can be a great idea for several reasons. It is good utilization of space that may not be used otherwise. In a home where there is an inadequate number of bathrooms, one more will always be welcome. If space is not an issue you can create a luxurious basement bathroom for yourself; a kind of indulgence. However being underground means that there could be certain obvious limitations with regard to ventilation. Ventilation is important not only for getting rid of odors, but also to let in fresh air and prevent the growth of mold, etc. in the bathroom.
General guidelines for ventilating a bathroom
The term CFM is used to refer to exhaust fans for bathrooms – CFM stands for Cubic Feet per Minute. The size of the fan that you install will be determined by the size of your bathroom. A smaller bathroom (of less than 100 square feet) may only need one 50 CFM fan used intermittently (not continuously). Larger fans of over 50 CFM are usually recommended for larger bathrooms.
Also note that if you have enclosed areas within the bath, such an enclosed shower area or an enclosed toilet enclosure, you may need to install more than one exhaust fan. While you can install one large fan to cover the entire bathroom, more than one smaller fans will do the job better by providing effective ventilation as and when required. Experts recommend that an enclosed toilet in particular must have its own ventilation such as an operable window or a dedicated fan.
What should also be kept in mind is the sort of tub you have in your bathroom: a jetted tub may need a larger fan than a regular tub. The positioning of the exhaust fan should ideally be close to the showering area or over the bath tub; which are likely to be the most humid sections of a bathroom.
Basement bathroom ventilation
The most important point to keep in mind is the fact that basement bathroom ventilation has to terminate out of door, open to outside air. So some amount of ducting will almost definitely be required to ensure proper ventilation that makes its way to the outside.
In the event that your basement bathroom is towards the front of the house, the ducting for ventilation may terminate towards the front of the house. In the alternative, a longer duct will have to be created so that it terminates towards the back or the side of the house.