Bathroom Ventilation Needs for SummerIs opening a window adequate bathroom ventilation in summer? Warm water vapor produced by bathing and showering condenses on bathroom surfaces, creating a chronically damp environment that supports mold and mildew growth, as well as bacterial contamination. In addition, bathroom moisture deteriorates drywall, peels paint and wallpaper, and warps doors and drawers. Over a period of years, water vapor seeping into bathroom wall cavities and ceiling space can rot wooden structural members, too.

Most residential building codes require either an openable window or a powered exhaust fan in home bathrooms to remove moist air. Summer weather here in Indianapolis is typically hot with daily relative humidity averaging 70% or more. Simply opening a window to remove bathroom heat and water vapor is less effective when the climate outside is also hot and humid. Conversely, a powered exhaust fan installed in the bathroom wall or ceiling induces active airflow, pulling warm moist air out of the bathroom space and exhausting it directly into outdoor air, regardless of weather conditions.

Here are some important factors about bathroom ventilation fans to keep in mind:

  • Recommended air-moving capacity of a ventilation fan is one cubic foot per minute (CFM) per square foot of bathroom floor space, with a minimum of at least 50 CFM.
  • Bathroom vent fans must be ducted and the vent duct must extend all the way to an outdoor termination point. Bathroom fans must not exhaust moist air into the attic, crawl space or wall voids.
  • For best results, a bathroom vent fan should continue running for 15 to 20 minutes after bathing or showering is finished. Occupants of the bathroom have typically left the room by that time. Therefore, a fan timer switch that is activated manually, then keeps the fan running for the recommended extended time period before shutting off automatically, is a better option to ensure optimum ventilation than a basic on/off switch.

Ask the HVAC pros at Mowery Heating, Cooling and Plumbing for more information about optimum bathroom ventilation.

Our goal is to help educate our customers in Brownsburg, Indiana and surrounding areas about energy and home comfort issues (specific to HVAC systems).