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

CLT walls and insulation

ultra_archie | Posted in General Questions on

Hi everyone, first time post asking a question that I hope some of your experience can help with. I’m working on a design for a cabin with CLT walls and floors. We’re applying rigid insulation (neopor gps panels) to the underside of the floor but have a potentially crazy question for the walls.

According to code in the project area (zone 3 in North Carolina), when using mass walls the required r-value is only R5 or R13 if more than half insulation is on the interior side of the mass wall. The CLT we’re using is 100mm thick and has a R-5 by itself. Does that mean that we don’t need to apply any insulation? I’ve attached a screenshot of the code.

If that’s the case, is it crazy to not apply some exterior insulation and just rely on the thermal of the CLT? Is that asking for trouble?

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. Expert Member
    DCcontrarian | | #1

    There is no scientific reason why mass walls should have lower R-values than other types of walls.

    There is a certain level of practicality in the energy code, at the end of the day it's all about cost-effectiveness. I believe that the reason the lower requirements were put in for mass walls was simply that they're harder (ie more expensive) to insulate than framed walls.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |