How to Replace an External Duct Flap

External vent flaps are placed inside hooded vents to prevent access to your interior ducts system by pests and to keep the vent from being a constant heat-discharging opening from your home. They also help to remove some of the fumes created by appliances in your home such as a stove or dryer. When the flap’s damaged, you not only lower your heating and cooling efficiency, but you also risk having the vented fumes blowing back into the structure as well. To replace a flap when necessary, all that’s needed is to replace the vent hood. The replacement hood has a new flap already in place, ready for use after the short replacement process.

Utility knife
Putty knife
Screwdriver
Replacement vent hood
Metal duct tape
Drill with bit set
Screws
Silicone sealant

Instructions

- 1
  Cut any sealant surrounding the vent at wall into 3-inch long sections with a utility knife. Pry the sealant away with a small putty knife.
- 2
  Remove the screws holding the vent hood in place with a screwdriver.
- 3
  Pull the vent hood from the wall slowly, making sure not to slide the ductwork out of the end of the vent tube that extends through the hole to the structure’s interior. Pull the crimped end of the duct off hood’s tube.
- 4
  Place the crimped end of the duct inside the tube of the new hooded vent. Place a strip of metal duct tape around the joint at the connection of the duct with the tube.
- 5
  Push the new hood into the hole in the side of the building, positioning the flap inside the hood with its hinges at the top. Screw the new hood into place.
- 6
  Place a bead of silicone sealant between the vented hood and the wall.

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