I can't find your first reference, though I did find the site. Exactly what is "scary?" And what is "ridiculous?

The pros and cons of both Building Science systems are discussed in the documents.

What do you mean by "moisture lock"? With either system, condensation is not a problem, unless perhaps you are building in Antarctic cold.

The URL you pasted for foil-covered polyiso doesn't work. The extra energy efficiency you quote has to be balanced against the much greater cost for polyiso vs. XPS.

The biggest drawbacks to installing exterior insulation--and I have done it as part of a waterproofing retrofit--are adequately protecting the abovegrade portion of the insulation in a cost effective manner and, in certain regions, termite control. Installing interior foam board is simpler, but contrary to the Building Science schematics, I would frame toward the interior to provide concealed spaces for wiring and utility boxes.

Here are the two systems the OP is questioning and wants to combine:

This post was edited by worthy on Wed, Aug 7, 13 at 11:20

Thanks for the reply.

Constant heat loss through my wall so my energy bill is always high is scary to me.

I was looking at some of configurations on Building science and some are listed as "not all configurations recommended"
so i thought i would ask here about the configuration i was looking at.

I was looking at combining the 4 inch exterior with the 2 inch interior with airspace and foil-back foam, not the $inch and ICF that you pictured... i will try to post pics.

Please note the below image was not part of my original post but would grateful to have it be considered in this question.

The reason for building out is to have somewhere to run electrical in the walls. If the foil back does nothing as you say maybe i would be better with 2inch & fiberglass or worst case just the fiberglass.

On the outside i was hoping to parge or use cultured stone, not sure these are good solutions.

As to ridiculous i just thought approx R43 basement walls might be a tad on the ridiculous side, maybe not though...sort of new to this stuff.

Here is a link that might be useful: This lets me post pictures easy.

Ooops DP.

This post was edited by Noctua on Wed, Aug 7, 13 at 12:58

I wouldn't even try to retrofit XPS on the exterior. (Unless you like hand digging for fitness and fun!)

So on the interior, the simplest, cheapest effective way to insulate is to put foamboard on the foundation followed by fibrous insulation to meet the minimum R value in your climate zone. Around the rim you can either foam (closed cell is best) or cut to fit XPS and seal with caulk or handheld foam.

For cold regions, one inch of XPS should be sufficient; for very cold regions, two-inches would be safer.

Building Science Corp. Climate Map

Here is a link that might be useful: Building Science Corp.: Basement Insulation Systems (pdf)

Rather than smothering the basement in R43, you might get more effective savings abovegrade sealing all cracks.

As a matter of interest, the first US house built to PassivHaus standards boasted an R-56 foundation with 14 inches of sub-slab EPS insulation, R-60 walls and roof and triple-glazed Thermotech windows with foam-filled fiberglass frames.

{{!gwi}}

Here is a link that might be useful: Building Science Corp.: Basement Insulation Systems (pdf)

This post was edited by worthy on Wed, Aug 7, 13 at 15:41