KentT - you asked for the shortcomings of using exterior foundation foam. Exterior insulation in general has been shown to be the most effective insulation and I have used exterior foundation insulation in past years on many homes. The shortcomings seems to be mainly the insect problem which has yet to be solved. (UV deterioration is another but that one is easily dealt with) Your quotes indicate that Dow recommends regular applications of poison on the ground around the house, which to me is another shortcoming and one of the reasons I rarely install foam in that location any more. I am also north of current termite range,so the relevant pest here is carpenter ants. That Dow states on their website that it isn't insect proof is obviously CYA, but it also indicates that there are limitations to the effectiveness of the built in insecticide. To me, the combination of needing to continually add poison around my home and knowing that the manufacturer won't stand behind their product (insofar as insect infestations) is reason enough to move the insulation to the interior where that is an option. Obviously only my opinion.

Thanks, Bob. I certainly don't mean to come across as confrontational -- I sincerely appreciate your (and other) opinions...

I think part of Dow's CYA is because there aren't 20-25 year longitudinal studies to show how it works over time... but it has certainly approven to work in shorter-term tests. Because the chemical is integral and mixed in the foam as it is made, it should last longer and be effective longer than just as surface application of it, but only time will tell...

Continuing to think about this, and the use of the basement slab as solar mass, I think I will let the concrete pour continue to the interior basement walls, with no insulation between, as a thermal barrier. That will seal that potential avenue of access, while also letting me use something like borate-treated foam (rather than BlueGuard) under the slab. It will also let the 10" CIP concrete walls serve as mass also. The BlueGuard would only be used as external insulation, covered by Tuff II coating or equivalent...

So, if the dreaded ubiquitous hordes of termites drill wholes in the insulation, clear into the middle of the slab, what will they eat once there?