Two questions with regard to your interior basement walls. 1. Why did you decide to have the concrete exposed and sacrifice the insulation value of the standard ICF forms? 2. Did you compensate the insulation by adding additional EPS on the outside of the wall?
There were a couple of reasons for the exposed interior concrete walls. First, we liked the looked of having exposed concrete instead of the super-common gypsum board dry wall usually put up over the inner EPS with standard ICF. Second, having insulation on the inside of the concrete mass would mean that it would be decoupled from the interior (not perfectly, of course) with respect to acting as a thermal mass.
Because this is a Passive House, there is a lot of exterior insulation, regardless of the structural wall technology, i.e. wooden studs in a stick-built house versus concrete versus any other form. So, even if we used the more common two-sided ICF, we would still be putting more insulation on the outside. With our exposed concrete “one-sided” ICF, that meant maybe another inch or two on the outside.
The basement walls from the inside to the outside are 8″ concrete, 2.5″ EPS ICF, 11″ EPS EIFS glued to the ICF, some sort of mesh glued to that, and then a plastic dimple mat. Ground floor walls will be identical insulation, but the EIFS will be finished with a drain plane and stucco finish.
I hope that answers your questions clearly enough, but if not, let me know. I’m happy to talk about our project.
Sweet Tree Passive House 
Two questions with regard to your interior basement walls. 1. Why did you decide to have the concrete exposed and sacrifice the insulation value of the standard ICF forms? 2. Did you compensate the insulation by adding additional EPS on the outside of the wall?
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There were a couple of reasons for the exposed interior concrete walls. First, we liked the looked of having exposed concrete instead of the super-common gypsum board dry wall usually put up over the inner EPS with standard ICF. Second, having insulation on the inside of the concrete mass would mean that it would be decoupled from the interior (not perfectly, of course) with respect to acting as a thermal mass.
Because this is a Passive House, there is a lot of exterior insulation, regardless of the structural wall technology, i.e. wooden studs in a stick-built house versus concrete versus any other form. So, even if we used the more common two-sided ICF, we would still be putting more insulation on the outside. With our exposed concrete “one-sided” ICF, that meant maybe another inch or two on the outside.
The basement walls from the inside to the outside are 8″ concrete, 2.5″ EPS ICF, 11″ EPS EIFS glued to the ICF, some sort of mesh glued to that, and then a plastic dimple mat. Ground floor walls will be identical insulation, but the EIFS will be finished with a drain plane and stucco finish.
I hope that answers your questions clearly enough, but if not, let me know. I’m happy to talk about our project.
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