Hello: I was thinking about using 12.5 SIP's (R-54)as the floor on a 1200 sf, single-story house built over a un-insulated crawl-space surrounding very uneven bedrock. This will cost about $7,900. So, I was wondering if there was a less expensive way? Any ideas would be appreciated. Rob.

What's your location? (Local subsoil temps may play a factor here.)

My house will be built 80 miles north of Montreal, Quebec, Canada. As mentioned, it will be built over exposed bedrock. See picture: https://www.dropbox.com/s/001adfmij4byctv/111.JPG Thanks, Rob.

If you insulate the sidewalls of the crawl space to be about the same as the conditioned space walls and apply a drainage layer of screenings/gravel over the bedrock you can then use roofing EPS at about half the R-value of the wall directly over the drainage layer. It'll need a vapor barrier in the stackup as well. The vapor barrier is best applied above the EPS if you're installing a slab, but between foam & slab works too.

Posted By Dana1 on 21 Nov 2012 02:04 PM
If you insulate the sidewalls of the crawl space to be about the same as the conditioned space walls and apply a drainage layer of screenings/gravel over the bedrock you can then use roofing EPS at about half the R-value of the wall directly over the drainage layer. It'll need a vapor barrier in the stackup as well. The vapor barrier is best applied above the EPS if you're installing a slab, but between foam & slab works too.

Thank you Dana1.