Choosing the proper ventilation for a bathroom requires four considerations: size, sound, operations, and location. To meet the International Residential Code requirement, the minimum-size exhaust system must be 50 cfm. To determine the cfm for a properly sized exhaust system in a larger space, use this formula: W x L x H x 8ACH = cfh. Then divide the cfh figure by 60 for the required cfm. Once correct cfm is determined, a remodeler must think about the sound level of the ventilation unit. If a fan is too loud, the homeowner might not use it. Exhaust systems that operate at a low volume are available, while remotely located fans are a quiet option and could vent two bathroom spaces with a single fan positioned in the attic. The exhaust fan should be controlled by a timer switch or humidistat. Because moisture can remain in the ductwork four hours, it is suggested that a bath fan remain on for 20 minutes after the bather finishes showering. A humidity-activated switch is an option. Regardless of the kind of switch chosen, the IRC mandates that it not be placed close to the bathtub or shower. And finally, consider that bathroom ventilation is needed for two purposes: odors and moisture. Therefore, the ideal location for the exhaust areas will be near the toilet, possibly in a side wall, and above the bathtub. | Read More