How to Connect a Bathroom Vent to an Existing Attic Vent

A bathroom fan needs to connect to an external vent, located either in the house’s roof or the gable. If not, the humid air from the bathroom blows into the attic, where it can cause mold growth and water damage. If you find that your house has a vent that is open, you may attach the bathroom fan to it using a flexible duct. The existing vent you hook the flexible duct up to must have a lip on the inside of the attic for the installation to be successful.

Measuring tape
Duct elbow
Sheet metal screws
Phillips screwdriver
Flexible duct with insulation sleeve
Hose clamps

Instructions

- 1
  Climb into your attic and measure the distance between the bathroom fan and the vent you plan to connect it to. This measurement helps you find a flexible duct that can span the distance between the fan and vent.
- 2
  Slide a metal duct elbow onto the bathroom fan’s exhaust port. Drive sheet metal screws through the exhaust elbow and the lip on the fan’s exhaust port.
- 3
  Slide one end of the flexible duct onto the open end of the duct elbow. Slide the insulation sleeve over the flexible duct, starting at the free end of the duct, until it covers the entire duct. Tighten the hose clamp over the flexible duct and the pipe elbow using a screwdriver, stopping once the flexible duct cannot shift in any direction.
- 4
  Secure the flexible duct to the lip on the vent’s opening inside the attic, by tightening another hose clamp over the connection. Place the hose clamp over the insulation sleeve as well, ensuring that it does not slide down, exposing a portion of the flexible exhaust later.

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