GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter 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

Insulate Half of a Basement Wall

Andrew G | Posted in General Questions on

I’m in central Maine. I’m going to be insulating my basement walls soon with Thermax. The walls are 6’4″ tall. I’m wondering if I could just insulate the top four feet of the walls because that is where the greatest heat loss occurs. People have also said that this would help things in the event of a leak, but code seems to require it along the entire basement.

I do have one hairline crack in my foundation that does leak a few drops during heavy rains. I’ve used a water proof caulking made to fix these issues and it has helped a lot, but I don’t trust the repair for the lifetime of the house.

Has anyone had experiences with insulating a full vs. the top half of a basement wall.

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. GBA Editor
    Martin Holladay | | #1

    Ideally, you should solve the moisture entry problem before you insulate your basement wall. For more information on this issue, see Fixing a Wet Basement.

    If moisture entry weren't in the picture, the answer to your question would be simple: You always want to insulate the entire concrete wall, not just the top half of the wall. Concrete is a fairly good conductor, so if you just insulate the top half of the wall, you are leaving a massive thermal bridge which defeats the insulation you just installed.

    If you want to install just the top half of the wall, in order to allow you to monitor moisture entry through the cracks, I suppose that you could. But that would be an unsatisfying installation, from both a thermal perspective and a moisture perspective.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |