Having a dedicated fan for the bathroom is an extremely effective way to remove unpleasant odors and prevent moisture buildup, which can attract mold and other allergens. Bathroom fans also help to preserve a home's walls and floors, which will suffer steady damage if regularly exposed to damp and heat.
Bathroom Fan Styles
Bathroom fans commonly come in two varieties:
- Impellers - blade-based mechanisms most frequently associated with the typical fan
- Blowers - circular latticed structures which tend to be more effective at keeping air flowing throughout the room.
Either fan works by circulating air into ducting or a central exhaust system, which then carries the flow to the exterior of the home.
Bathroom Fan Ratings
The effective power of a ceiling fan is commonly measured in units of CFM, or cubic feet per minute. One can determine the airflow rating required for a given room by measuring its length, width, and height, multiplying these together to determine the room's volume, then dividing the resulting number by 7.5. This will yield the CFM rating, which is usually displayed on the fan's box.
For example, a room 5 x 9 feet in size and 8 feet tall has a volume of 360 feet; dividing this by 7.5 would thus indicate a minimum flow rate of 48 CFM is required.
Meeting the CFM rate should allow the fan to entirely clear the room of air two or three times in twenty minutes of operation, effectively preventing any moisture from being retained in the walls or floor. One can ensure that a fan has had the opportunity to run the required twenty minutes by installing a timer with an automatic shutoff. Such a feature will prevent the wasting of energy should one forget that the fan is in operation.
Bathroom Fan Noise
Low-quality bathroom fans can be fairly noisy, with quieter units predictably requiring a larger investment. A fan's noise rating is measured in units of loudness known as sones, with the standard range for fans running from about 0.5 (almost inaudible) to 4.0 (a standard setting for electronic speakers). Quieter fans tend to require less in the way of wattage. A fan of 0.5 sones needs a flow of about 20 watts of electricity; while one of 4.0 sones may require up to 80 watts. So a high-quality fan is energy efficient in addition to contributing to a noise-free environment.
Poor installation may also contribute to noise levels if the fan rattles excessively; using screws instead of nails can help to prevent this annoyance. In addition, sharp turns in the exhaust ventilation may create an excessively loud flow of air. This can be avoided with a well-planned ducting system.