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Airtight electrical boxes

fall50 | Posted in General Questions on

Long time reader……we have 1940’s 1.5 story in MN far from air tight but have made some strides with air sealing etc. One thing we have been dealing with in this recording breaking summer of high dew points and humidity is a faint order or musty/cigarette smoke if I put my nose right up to the switch plates and electrical plates. Some being worse than others. Now quick background the prior owners did smoke and inventively I understand much of that smell is probably behind the walls.

We do have central air and when its on….. the faint odor seems to be greater in my opinion… Now I’m well read on ADA drywall approach etc along with using airtight electrical boxes etc. Because I’m almost certain this smell is not due to mold/moisture as a few of the walls are interior walls with no water pipes etc near them. I believe this is most likely moisture laiden air coming in from the outside mixing with year and years of cigarette smoke present behind the walls.

I guess my long winded question because the drywall/plaster is certainly not air tight at the bottom plates would it be worth trying to switch a few these electrical boxes out for airtight ones which include the gasketing etc. Will the air infiltration just find another path to infiltrate from? I don’t want to start monkeying around with swapping electrical boxes if the net result will be barely noticeably.

I would also like to get opinions on leaving the existing boxes in place and very carefully using a few very strategic squirts of canned foam in any penetrations within the original boxes. Note I do have a foam gun which attaches to the great stuff can foam. Of course the pereminter of the boxes will also be addressed for any openings bewteen the box and the drywall. Of course any excess foam within the box would be cleaned out.

Also could be due to the HVAC system being unbalanced I suppose with the main floor being under slight negative pressure.

Thanks in advance

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  1. jklingel | | #1

    I'm only a DIY guy, but it would not surprise me if the sheet rock, insulation, switches themselves and the wires, esp with the "cloth" wrap around old wires I've seen (if you have that type), stink. Have you pulled any switch/wires and smelled them? Any way to "do up" one room (all penetrations, new paint, etc) and see what happens?

  2. GBA Editor
    Martin Holladay | | #2

    Careful squirting can help a lot. But remember, introducing foam into an electrical box is a code violation. It also increases the chance of fire. So use common sense, and don't fill the box.

  3. user-659915 | | #3

    Caulk (rather than foam) the box penetrations, no?

  4. user-659915 | | #4

    And John K's points are good ones. Have you tried sniffing the wall surface AWAY from the electrical boxes? The cigarette smell may be in the paint/plaster. And how about a thorough electrical inspection. Not good if your cigarette stink is actually smoking wire.

  5. Jon_R | | #5

    Consider a device to control interior pressure such that you never get infiltration. No only will it stop the cigarette smell, but it will help with latent load.

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