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Air-barrier details

harrison55 | Posted in Green Building Techniques on

We are planning a pretty-good-house, with a target blower-door test of 2.0 ACH @ 50 Pa.  We will have Zip-R1.5  sheathing on the walls and use low-density foam to obtain the roof air barrier. 

GBA has plenty of good info on wall and roof design, but I could use some help with issues in detailing:

1) Bathroom and kitchen venting: What is the best set-up for “air-tighting” the 4″ exhaust ducts?

2) Dryer vent (for a gas-fired conventional clothes dryer; a condensing dryer is not an option):  What is the best set-up for “air-tighting” these 4″ exhaust ducts?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Mark,
    Q. "Bathroom and kitchen venting: What is the best set-up for “air-tighting” the 4 inch exhaust ducts?"

    A. A bathroom exhaust fan is usually located in your bathroom ceiling. Typically, the air barrier in this room is the ceiling drywall. As long as you include caulk or a gasket between the ceiling drywall and the exhaust fan housing, you have a ceiling air barrier.

    For more information on this issue, see these two articles:

    "Bathroom Exhaust Fans"

    "Air Sealing an Attic"

    Q. "Dryer vent (for a gas-fired conventional clothes dryer; a condensing dryer is not an option): What is the best set-up for “air-tighting” these 4-inch exhaust ducts?"

    A. Choose an exterior termination with a good backdraft damper. Here is a link to one commercial product:
    https://www.truevalue.com/dryer-vent-seal-4-in?ctplacement=271426-43411605579&cid=gooshop

    You'll be using galvanized ductwork to vent your clothes dryer. Use a high-quality caulk to seal the crack where the duct penetrates your air barrier.

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