[Greenbuilding] ABout how thermal mass of ICF would work

[Beatrice Dohrn]

Hey all. 

I'll be building a house (for myself) this summer (near Eugene Oregon). 

Some time ago -- and with some help from responses on this list -- I decided to change from a longstanding plan to use the more common insulating concrete forms (the ones that used EPS in and out, etc) and have engineered to use faswall,  produced right near here by shelterworks.  This type is demineralized woodchips,  with a slot in the outside 1/3 of the cavity for 3" of  insulation (you can choose,  EPS, Min wool, or Polyiso).  

I just spoke iwth the rep from the company I am NOT using,  explaining my decision as a courtesy.  I got an annoying sales job, of course.  I wanted to test one thing she said -- out of curiousity really as I am not changing my plans now.  Question is this:

I believe that the faswall ICF makes the thermal mass at issue more useful to the house's temp because it is not insulated away from the living space -- as is the case with EPS ICFs.  The rep from the EPS co suggested to me that "heat seeks cold" and that therefore in the winter the walls would "draw" the heat we generate in the house down into the ground -- since the concrete core goes below the house into the ground ( in my case a lot, as we have a basement).  This goes against about 50 things I thought to be true about how thermal mass like this will work.  Do you think it's true?


Beatrice Dohrn