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Air Sealing Electrical box knockouts

fall50 | Posted in Energy Efficiency and Durability on

In an exsting electrical box can the knockout or “cutouts” in which the wire runs through be sealed off by spraying a small amount of canned spray foam. I would take the plate off, pull the wire out of the box as I dont want any overspray inside the box

Of course special attention would be given as to not “overspray” the inside of the box causing the wires inside the box to be envloped in foam.

Also can canned foam which claim to have a Class 1 Fire rating be used around a dryer ducting which goes through a cider block wall. The cutout in the wall is 2-3 inches bigger than the metal uct.

When I spoke to manfacture of the gas dryer he indicated the max temp for most resendtial gas dryers is around 180-200. Usually measured right behind the unit….Keep in mind the portion I was considering insulating the temp will be less. I will include the tech bulletin from DAP

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  1. GBA Editor
    Martin Holladay | | #1

    To answer your first question, I wouldn't use spray foam to address air leakage through conventional electrical boxes. Because of the problem of overspray, your attempt may be considered a code violation by your electrical inspector. The volume of air in an electrical box is required to prevent overheating of the conductors.

    Several manufacturers and distributors produce special electrical boxes or box accessories for airtight installations. These include:

    Allied Moulded Products


    American Aldes

    Energy Federation Inc.


    Pine Ridge Builders

    Shelter Supply

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