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

Poor Man’s Thermomass

ethan_TFGStudio | Posted in Green Building Techniques on

The previous conversation got off on a tangent about material costs and PWF… There was not much uptake on my “Poor Man’s Thermomass” idea: https://www.greenbuildingadvisor.com/sites/default/files/poormansthermomass.jpg

Since drawing that detail, I have thought about replacing the EPS with rockwool, and have done some research on what the backerboard could be. I understand it can’t be Hardibacker or Durock. Perhaps there is another subgrade cementitous board which would be applicable?

I see Finex are OK for ground contact (http://gofinex.com/en/fiber_cement_panels_finex.php#ground). I also looked into T-Clear Wallguard (http://www.tclear.com/products/wallguard/) which is a cement board fused to insulation. They told be that the rockwool version is not suitable to below grade applications, but I wonder if this is in line with the new thinking of below grade rockwool…

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.

Replies

  1. onslow | | #1

    Ethan,

    Missed your first posting about poor mans thermomass, but I can see from the image on the link that you are very close to exactly what I have done on my own home. Rather than make a too long post, I would be glad to exchange notes directly if that is of interest. I think if you ask the moderator, he will send you my email. I am a bit hesitant to post it here what with the frequent invasion of sneaker offers and the like.

    A real short version of what I have is 3" XPS salvaged foam shot to the foundation with special ramset anchors, complete incapsulation with Grace bitumen based sheet, and 1/2" hardi board skirting over that to combat rodents and sunlight. I don't believe it is relevant to go with a hard surface over the entire foam sheet all the way below grade. For what it is worth, I think the Thermomass idea has a few critical failings in the way walls must be cast. There is more thermal bridging occurring than first meets the eye.

    I am in a 6500-7000HDD climate and my basement stays at 58 with no heat, a condition I will be taking care of now that I have time to be down there. Approximately 20 percent of my wall area is above grade and sees temps as low as 15 below. (not often though) Ground water is a major concern and I can detail all the efforts I took to control that problem.

    Hope your still in planning phase as some choices will demand finding a contractor willing to do what will seem odd to normal practice.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |