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I'm putting a subpanel in the outside wall of my attached garage, which I'm also insulating so I can work out there in the winter. I'm wondering what steps are worthwhile to air seal and insulate around the subpanel. The wall is 2x4 framing, so there isn't really any room for insulation behind the box.

  • Would it be beneficial to try fitting insulation in the rest of the bay (above/below panel) or should I just focus on air sealing?
  • Can/should I use caulk to seal the cable clamp penetrations?
  • Should I do something to block airflow through the conduit which will connect the subpanel to the main panel?
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Have you considered using a surface mount box which would allow more space for insulation in the wall behind the electrical panel?

You should definitely do as much as you can to prevent air leaks.

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Yes, insulate above and below to the best of your ability. Do not shove anything into the conduit or your going to have one pissed off electrician next time something needs doing. The 14in x ~2ft hole (the sub panel) in the insulation is negligible compared to any air infiltration that may be coming from outside. IE, the garage rolling door, poor construction, lack of house wrap, ect.

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