How to Insulate a Bathroom Vent Fan

Written by elizabeth knoll
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Bathroom vent fans installed in attics that get cold should be insulated to prevent condensation problems. Warm air from the bathroom below pools inside the fan. The only separation between this warm air and the cold attic air is the fan's thin sheet metal housing. The temperature differential can be enough to cause condensation and moisture issues if the housing is not properly insulated. A bathroom fan can be insulated easily with regular foil-faced duct insulation.

Skill level:
Moderately Easy

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Things you need

  • Tape measure
  • Utility knife
  • 3-inch foil aluminium tape

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  1. 1

    Measure the dimensions of each side of the bathroom vent fan in the attic, using a measuring tape. Measure the top of the bathroom vent fan.

  2. 2

    Cut each piece of duct insulation at those measurements with your utility knife.

  3. 3

    Fasten each piece of insulation to the fan with 3-inch foil aluminium tape. Tape the insulation directly to the fan housing. Trim the insulation as necessary with your utility knife to fit around ducting and electrical connections to the fan.

  4. 4

    Tape the insulation seams together once all the insulation pieces are fastened to the fan. The fan will now look like it has a single foil-faced insulation jacket encapsulating it.

Tips and warnings

  • Before insulating your exhaust fan, make sure it is rated IC for insulation contact. This rating, if applicable to your fan, is listed on the fan's service tag. If the fan isn't rated IC, it cannot be insulated.
  • Wear a dust mask and safety glasses when using duct insulation. The fibres can irritate your skin, eyes and breathing passages.

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