Hi, I'm in the middle of a bunch of renos and about to order materials. My plan is to excavate to the footings and add 6" of EPS foam to the foundation up to and above the subfloor. Then remove the alum siding and add 4" of EPS to the existing 2x4 exterior wall. I think it would be easiest to do hardiboard siding myself (although I'm certainly open to stucco), and so at first I thought it would be best to strap out the foam for securing the siding. Then I started worrying about how to fasten the foam. With 4" of foam and half an inch of OSB, I'd need pretty long screws to make it into the studs AND with the weight of the Hardiboard, would it be enough to hold the strapping? (Strapping could be 1x4, or 2x4s) Or might it be possible to glue the EPS to the existing OSB, and then glue more OSB to the EPS? Obviously it wouldn't be possible to have any vacuum sealing going on, but it won't really be structural either. I'm going to replace all the windows and doors, but have them recessed back to the original walls. Advice?

What you have in mind is not SIP construction. You should post this in the Energy Efficient Building & Construction Forum. There are definite issues to consider when applying foam insulation to the exterior of an existing wood frame home regarding climate and moisture management.

Thanks, I moved it - what kind of moisture problems? I was also considering adding an acousti-sealed poly vapour barrier to the OSB before I put the foam on. With the strapping, the siding should be able to breath.