GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Why worry about electrical boxes when sheathing is airtight?

joenorm | Posted in General Questions on


I am starting my electrical and was wondering how air would be infiltrating through boxes if the sheathing is supposedly airtight?

Is it simply because no system is perfect? So its additional precaution knowing the wall is not perfectly sealed from the exterior? Thanks!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Jon_R | | #1

    Partly because no system is perfect and partly because air flowing from the interior, to a cold surface and then back to the interior can cause condensation/sorption problems. Interior side and exterior side air barriers are not equivalent.

  2. Expert Member
    BILL WICHERS | | #2

    Just like Jon said, sealing the boxes is in part belt and suspenders, but it also helps to keep warm inside air from getting into the wall assembly and causing condensation problems. If you are using a lot of exterior rigid foam condensation issues are much less of an issue, but the extra air sealing is still a good thing.

    Having multiple layers of air sealing is similar to having double gaskets on windows. There is always a little bit of leakage, and the second layer helps to knock that total leakage down even more.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |