Hi, I am a heating and cooling guy trying to get an accurate heat loss calc done on an SIP house. The builder tells me that an engineer from the SIP manufacturer calculated this 2100 sq foot house with a conditioned 1500 sq ft basement. They said that the heat loss on the house would only be around a ton and a half. This is in southern wisconsin where a similar stick built house would have at least twice this heat loss. I am pretty unfamiliar with sips so I don't know how to calculate loads using them. Are the numbers the engineer came up with too good to be true?

The windows would be a bigger factor than the walls.

Possible with good windows etc.

I am in a harsher climate and I expect to be below 10 btu sq/ft

R-Control did a side by side comparison test of a 2X6 stick framed and fiberglass insulated room, one door, one window, to a 4-1/2" SIP walled room with one door and one window. Although the stick framed room had an advertized R-value of 19, and the SIP room had an R-value of 14.9, the SIP room required 9% less heat energy to keep it at the same temperature. The truly significant finding was that at 50 pascals of negative air pressure, the stick built room leaked 126 cubic feet of air per minute, while the SIP room only leaked 9 CFM's. It becomes very apparent that the success of a SIP home is a combination of high R-value, air tightness and energy efficent windows.

Steve
GrandCountySIPs.com

Around $100/year doesn't surprise me. How was the stick room sealed - plastic vapor barrier, exterior foam, house wrap?

Actually, the test was done by Oak Ridge National Labratory. The report on SIP vs stick, and much more information, can be found at:

http://pims.ed.ornl.gov/US%20Kazakhstan%20Working%20Group%206-04/building%20material%20presentation.pdf

Steve
GrandCountySIPs.com

Actually, test results or details aren't there or in the invalid first link it references.