Ventilation with Your Bathroom Exhaust Fan
An exhaust fan in the bathroom serves three primary purposes. It helps to eliminate odors, reduce humidity, and remove airborne pollutants. In the bathroom, moisture and humidity are produced from running water, flushing toilets, steam from showers, and even under-sink leaks. Odors, harmful chemicals from aerosol body care products, and moist air from the shower can be removed by the bathroom ventilation fan. Experts recommend the fan be left on for at least 20 minutes after using the bath or shower.
Proper Use of Bathroom Ventilation
Most building codes call for a ventilation system to provide a full air exchange a minimum of five times every hour. Some professionals recommend eight full exchanges per hour. Air volume moved by the fan is measured in cubic feet per minute, or CFM. An easy way to obtain the proper rate of air exchange is to look for a fan rating that matches the square footage of your bathroom. An 8′ x 10′ bathroom would require an 80 CFM exhaust fan.
Location of Bathroom Ventilation Fans
In order to work most effectively, the bathroom fan should be installed near the tub or shower. Ideally, it would be located opposite of where air enters the room (usually the bathroom door) and not near an HVAC vent. If your bathroom has a separate water closet for the toilet, this area should have its own ventilation fan. In a large bathroom or a room with high ceilings, install additional fans or choose a model with a higher capacity.
Exhaust to Outdoors
The air exhausted from the bathroom should be vented to the outdoors. Venting to the attic makes for easier installation; however, an exhaust fan that vents humid air into the attic is only relocating the moisture issues elsewhere in the home. Moisture in the attic contributes to mold growth in the insulation and causes structural components, like joists and rafters, to become weak from water damage.
The bathroom fan should be vented out of the roof or directed through an upper part of the wall. Add screening to the end of the vent to prevent pests from accessing your home.