The Best Types of Ducts for a Bathroom Fan

Fan Placement

• The bathroom fan should reside near the shower but not immediately above it. A homeowner can use a stud finder tool for locating ceiling joists before deciding on a permanent fan installation location. The ceiling joists maintain the building's upper structural framing and cannot be altered. Designers can determine the best ductwork for that specific building's architecture once the fan has a permanent installation location.

Duct Composition

• The best type of ducts for a bathroom fan are short and rigid. Corner Hardware suggests using sheet metal ducting for a smooth internal surface. The rigid, smooth surface allows faster air movement from the bathroom to the outside as well as dampens fan and air motion noise. The ducting should be as short as possible for preventing moisture buildup within the duct's length.

Duct Shape

• The duct's diameter should not be smaller than 3 to 4 inches, states Corner Hardware. A smaller duct diameter reduces the bathroom fan's efficiency, causing extra noise and more stress on the fan's motor. The ducting should also remain as straight as possible. Multiple bends in the ducting hinders air movement efficiency, lessening the fan's effectiveness for clearing the humid air away from the bathroom.

Duct Placement

• The ducting can exit the building in three different ways. Bathrooms that do not have attic space above them can vent the humid air out through an exterior wall. Home bathrooms with attic space above typically route the ducting through a roof vent. A bathroom with a nearby soffit, or eave, strategically hides the outside duct vent on the underside of the home's overhanging roof structure. A homeowner must determine the best duct placement for the individual home, maintaining a short and straight duct installation regardless of the final outside vent location.

Benefits

• Trapped moisture within a bathroom contributes to mildew growth on the walls and moldy tile grout. A strategically designed bathroom fan and ductwork combination removes the sticky fog from the room, preserving the room's structural integrity. Over time, a poorly ventilated bathroom exhibits peeling paint as well as possible damage to the underlying wood framing and insulation.

Effective Fan Use

• Run the fan for at least 20 minutes after using the bathroom shower. This time frame allows the fan and ductwork to vent the humid air effectively. In fact, some bathroom fans are manufactured with timers. The homeowner sets the timer, allowing the fan to operate and shut down at a specific time, which is especially helpful when a person must leave the home quickly after a shower.