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Community and Q&A

Sealing remodel recess cans

Mark Attard | Posted in Green Building Techniques on

Does anyone have a good technique for sealing remodel recessed cans?

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  1. GBA Editor
    Martin Holladay | | #1

    Many responders will advise you to throw the fixtures in the Dumpster and cover the ceiling holes with drywall patches. But I won't go there.

    Do you have access to the recessed can lights from above? In other words, are they being installed under an attic or in a cathedral ceiling?

  2. Riversong | | #2

    I will go there. There is no excuse for installing recessed lighting in an insulated ceiling.

  3. Anonymous | | #3

    The location of these cans are in joist spaces between two floors.

  4. GBA Editor
    Martin Holladay | | #4

    If both the lower floor and the upper floor are heated or cooled, then the recessed can lights are not penetrating the home's air barrier and therefore do not need to be sealed.

  5. Anonymous | | #5

    Even if the joist space extends to the rim joist?

  6. GBA Editor
    Martin Holladay | | #6

    Conscientious builders include air sealing details and insulation at their rim joists. If the building you are talking about has no air barrier at the rim joist, and no insulation at the rim joist, then you have a problem -- no matter what you do with your recessed can lights.

  7. Anonymous | | #7

    They are all sealed. Just needed to confirm.

  8. GBA Editor
    Martin Holladay | | #8

    What are all sealed? Your recessed can lights or your rim joists?

    If you are talking about rim joists, what are they sealed with?

    Are your rim joists insulated?

  9. Anonymous | | #9

    Rim joists are sealed with a combination of foam and batt insulation.

  10. GBA Editor
    Martin Holladay | | #10

    Then you're probably fine.

  11. Riversong | | #11

    Perhaps, but if there are unsealed wiring or other mechanical penetrations from the joist bays up through the next floor walls, which might also have penetrations into the attic, then you have a problem.

    We tend to pay attention only to direct leakage paths, but channel flow (widely-spaced intake and exhaust leaks, particularly vertical) can far more dangerous because of the long flow path, more contact area and time for sufficient cooling to occur to reach a possible dew point.

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