I am planning to build an energy efficient home in upstate New York. The home will have a full basement, about half of which will be finished. Has anyone had any experience with foundation systems like the T mass wall where 2 inches of foam is sandwiched between inner and outer layers of concrete? Also from reviewing archives I see many people like the precast Superior wall system, has anyone heard of problems with precast foundations leaking? My site is well drained sandy soil. All advice welcome and appreciated!
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If you have well drained, sandy soil then I would not see the foundation walls as your primary heat loss as long as they are insulated. You should insulate the walls and the slab floor.
If you're using the same system on the exposed walls down there though, then ICF construction may make sense. If you're doing the same framing on the exposed walls you're doing elsewhere though, I don't see a real energy benefit to the ICF foundation walls...
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From what I have read, the big advantange of the 'sandwiched' foam idea was that exterior foam board and ICFs may be prone to insect infestation, as well as the issue about how to finish the exposed portions.
In termite areas, sometimes you apparently need to provide a 'bare strip' between exterior foam and the mudsill so that any termite activity can be seen. Something of a design challenge.
The other conventional alternative is to insulate the inside. Some say that it is better to have the thermal mass of the foundation on the 'inside', and a thermal break with the floor can be tricky.
The insect issue is the reason I am looking at alternatives to ICFs, although we don't have a termite issue around here we definitely have carpenter ants and the local exterminators tell me exterior foam above grade makes treatment quite difficult.
We are also in upstate NY. We usually recommend a conventional poured foundation with a framed insulated wall inside. If you are finishing the space, this is the least expensive alternative. Yes, you lose the thermal mass but unless you are using the mass to actively store heat, I don't think this is a significant loss. I would rather spend the money on other energy saving strategies.
You shouldn't have to guess on this. Get your contractor or subs to give you quotes on alternative systems. The theoretical benefits can be put in perspective with these quotes.
I built a home in Canton using Arxx ICFs for the basement. It was the warmest, driest, most comfortable basement I've been in. Having the high insulation value was wonderful.
For waterproofing I used Grace membrane. The perimeter drains drained by gravity to daylight.
Depending on where upstate you are, insects should not be a problem. Canton was too cold for insects. I believe many ICFs are available with or can be field treated with borates to eliminate any insect problems. They were not available in 1999.
Due to a job move I'm downstate in a spec home with a poured concrete foundation with fiberglass nailed to the concrete. There is no comparison as to how much worse the spec home is. The basement is always cold, and in summer I get condensation around the perimeter of the floor where mold grows. Next year I'm installing a dehumidifier and disinfecting the basement.