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Community and Q&A

Blocking Second-Hand Smoke and Air-Sealing

jmarting | Posted in General Questions on
Hi everyone!
I bought a condo and turns out the guy of the unit above likes to smoke himself inside his apartment, and the cigarette smoke (I am a first unit) comes into my unit, as well as odors from cooking.
The smell enters through the kitchen ceiling and the bathroom, I know it because I tested it by sealing the kitchen and bathroom with plastics. I opened the dropped ceiling of the kitchen to seal with Great Stuff the ductwork connection, the holes of the pipes that go to the second unit, and a couple more areas where I found air coming through.
I failed miserably.
Now, I am losing my marbles and plan on removing all the drywall of the ceiling. I need your help to tell me if this makes sense:
-Remove drywall of the ceiling
-Spray great stuff all over it. Turns out great stuff is not such a great air sealer, so here comes the next step
-Paint with Zinsser shellac primer on top of the foam, a couple coats. That should block potential vocs from the foam itself and increase the air sealer capabilities
What do you think?
*I am not considering regular 2 part spray foam because of potential health hazards
You don’t know how much I thank you for reading and helping me out, my wife is asthmatic and this is extremely frustrating.

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  1. Jon R | | #1

    Do try to seal air leaks. But you will only achieve complete success by pressurizing your space (so your neighbor's air doesn't enter your space).

    1. jmarting | | #2

      Thanks Jon. The kitchen is "sealed" with plastic, and with the extractor running (1200 CFM), I was able to tell where the air was coming from, with a small smoke generator machine.

      So in regards to the strategy of spray foam and then zinsser shellac primer on top, what do you think?

      1. Jon R | | #4

        I'd use a good tape (like 3M 8067) to air seal.

  2. Steve Knapp CZ 3A Georgia | | #3

    You might want to investigate Aerobarrier ( for air sealing.

    And in line with what Jon suggested, you also might want to install something like a Panasonic IntelliBalance to bring in fresh air and slightly pressurize the space.

  3. AlexPoi | | #5

    Aerobarrier is a good idea. It's expensive but you wouldn't have to remove the drywall. Otherwise you can try the airtight drywall approach but it a bit's more work.

    If you remove the drywall, forget about the can foam or the shellac. Shellac is not an air barrier and you'll never achieve good results with can foam (it would takes you something like 100 cans). You need a real air barrier like a thick polyethyelne membrane. One approach would be to remove the drywall, staples a polyethyelene membrane to the bottom of the joists (the thicker the better), then air seal with tapes all the penetrations and the seams, fur out the ceiling then reinstall all the drywall. The furring would allow you to run wire and put new electrical boxes if you ever need too without messing with your membrane. You would loose a bit of head room but that's the best solution if you go this route.

  4. Expert Member
    Zephyr7 | | #6

    If you’re worried about health issues from fumes, be SURE to ventilate your space while using the shellac primer (probably BIN?). That is some smelly stuff!

    A 1” layer of two part closed cell spray foam is probably your best bet for total air sealing. If you have an experienced installer apply it you won’t have any problems. Another possibility is some off-label use of a waterproofer like the liquid rubber coatings. If you roll these on thickly as they’re intended to be used, they form a pretty good air barrier. I’ve never tried using one of these on a ceiling though. I’d expect it to be pretty messy.

    Use mastic on ductwork, not canned foam. Mastic is good on many other little gaps too small for canned foam too.

    After sealing everything you can, keep your space at a slight positive pressure by using a fan to bring in outside air to pressurized your space. This ensures that any air leaks leak OUT, not IN, to keep smells out of your space. You should consider filtering that incoming air too, possibly with an activated carbon filter that will get smoke and smell.


  5. zw9191 | | #7

    Hello, I am having the same issue, and I am desperate to fix the problem. Did anything work? I have turned on email notifications for replies. Please let me know if you've found a solution.

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