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Any experience with ThermaEZE, Thermomass or similar cast-in place foundation insulation?

K T | Posted in Green Building Techniques on

link below from Certainteed-(insulation exposed, on inner wall of foundation)
2-4″ EPS insulation panel attached to wall form, with void space in-between filled with concrete foundation.×365.jpg

and Thermomass-(insulation sandwiched between concrete)

Would like to know if there are any cost/performance advantages of this approach to just adding foam to the interior after foundation is cast. And for the sandwich approach, if there’s still risk of moisture condensation on the interior concrete wall.


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  1. Mick McBride | | #1


    I have done a lot of research on Google trying to find any information I can on building a house using the cast in place method. It is the way I ultimately want to build my house and am having it designed as such. The main issue is there isn't a lot of information about using it to build a house and trying to find a contractor to do it is a challenge.

    There are many different companies that sell different concrete wythe connectors for cast in place or precast walls. - Has a section about condensation. - Has a section about moisture.

    I have a lot of these products and research done on these products bookmarked.

    I still haven't decided on cast in place or precast; I flip back and forth depending on which article I'm reading and the availability in my area.

    Thanks for taking me back down the rabbit hole.


  2. Jon R | | #2

    Yet another concrete/foam hybrid is "SCIP". A good system but not at all popular in the US.

    Foam on the interior side will need to be covered (for fire reasons). Foam on the exterior (or middle) has some thermal mass advantage. In all cases, think about thermal bridging (eg at the floor/wall intersection).

  3. Roger Berry | | #3


    At risk of being the skunk at the party, I would urge you to look more closely at all thermal pathways when considering two of the products you have supplied links for. I was going to attach snips of the relevant parts of two photos supplied by the manufacturers, but I am fearful of violating copyright laws as well as p---ing off the companies.

    For pour in place walls, either ThermoEZE or Thermomass, the down fall is the frequent thermal bridging brought on by the break-back ties used to hold the forms. These ordinary steel ties will cause a cold transfer pattern much like the one I see on my roof (pic below). ORNL did an analysis of the heat loss for a foam in the middle wall which demonstrated just how much of a hit is taken on whole wall R value. If I can find it I will attach. I was looking into all these alternates nearly 10 years ago and that hard drive is pretty wheezy.

    One picture clip I am not adding is from the cover of the ThermaEZE product brochure you linked to. Please note the form's break-back ties prominently showing just behind the blue plastic widgets that are piercing the possibly not code foam. An interior shot from the Bartley site of a Thermomass installation shows the break-back ties over the man's shoulder.

    I did research so far as to discover that there are indeed fiberglass rod tie-backs used in saltwater environment concrete works. Very expensive, plus unlikely I would get anyone local to risk a pour on an entirely new and one-off job.

    Whether having built in spots to shoot the interior drywall screws into is worth the effort and expense of the plastic widgets is also worth exploring. InsoFast might be a more practical product to look into for interior insulation of your basement. It would also be a good idea to check with an engineer and local people about how they will accept a two wythe wall and how they would want sill plates detailed. ThermaEZE is at least a bit more normal.

    I have attached my own photo of my own roof to show just how powerful the heat transfer is when using carbon steel screws. These particular ones are passing through 6" nail base into LVL rafters. The underside of the deck is a foam and batt continuation of the insulation profile. The snow is about 3" deep. Stainless screws would have been a wiser choice since the heat conduction is about half that of carbon steel. I would have also included a picture of the same effect on my standing seam roof panels when the morning dew will show hot spots. Unfortunately I don't mark my photos well and can't find it.

    The Dayton, Altus, and HK products seem to be very specific to tilt up construction which avoids the metal break-back ties. Tilt up panels require very different levels of engineering from traditional home building which would likely raise costs to an impractical level. Although a somewhat similar technique of panelizing concrete and foam board is used by Superior basements, I find the embedded steel base and top plates thermally suspect. As for costs, that would need to be reviewed as well.

    Sorry to sound like such a negative Nancy, but I reviewed pretty much all the same stuff and ended up just shooting 3" reclaimed XPS to the outside of the foundation and jacketing that with Grace Bitumen product. Half inch steam shower grade Hardiboard is hung from a designed in point on my wall flashing. A bit fussy to make tidy, but most everyone thinks that they are looking at a normal foundation if they pay any attention at all.

    So basically, yeah it is much less fuss, maybe less cost, and condensation inside the basement is not an issue at all. But my tolerance for humidity levels may be different from yours. Don't forget to insulate under your slab to at least R10 preferable R15 and provide a washed rock base for the foam. Calculate the heat loss for 12-1500 sq.ft. of R2 on a Delta T of 20 F and then appreciate how much load the basement actually is in an overall view. The ground will be that temperature 24/7 for 365. The above grade parts will see greater Delta T extremes, but at least for many climates, spend a good percentage near to 68-70 F or Delta Zero.

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