What's better: 4 inch SIPs with 2 inch XPS or 6 1/2 inch SIPs only?
This question is just about efficiency, not about cost. The house will be Thermocore SIPS, but we are trying to decide on 4" SIPS with 2" XPS on outside, or 6-1/2" SIPS with no foam.
4" SIPS = R-24 + R-10 for 2" XPS, total R-34.
6-1/2" SIPS = R-40.
once I figure the savings on the SIPS, but add the materials & labor for the foam, plus a couple of other items, the cost difference is almost a wash.
The R-value with the 6-1/2" is better, but using the 4" with XPS foam will eliminate the small bit of thermal bridging that will occur at the top & bottom plates, wall intersections, etc.
What would be better, the higher R-value, or less thermal bridging?
Posted Thu, 12/26/2013 - 12:18
Edited Fri, 12/27/2013 - 08:57
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