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Originally Posted by RobertSmalls
With some spray foam insulations claiming twice the stabilized R-value of cellulose, it might be doable with 8-9" walls with no thermal bridging, e.g. with steel studs. I wonder, would the increased cost of spray foam insulation be made up for by the savings in lumber, framing labor, window and door trim, and per-square-foot taxes?
Vacuum insulated triple glazing and 18" walls would be nice, but I view them as very expensive toys. I'm inclined to go with a very efficient, 2x6-framed, well sealed house with ventilation heat recovery and good, south-facing double-pane windows. Who knows; it might be passive nine months out of the year, and pretty close in August, January, and February.
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There may be an increased cost in spray foam insulation if you use it but if you go with Structural Insulated Panels with new construction, you avoid the framing labor, get a thinner wall than using fiberglass or cellulose. Since it is rigid foam inside, you have a built-in vapor barrier and air sealing that is hard to mess up too. Doing a little reading to see if these can be bought thick and it seems Wikipedia mentions that they can be 12" thick. If the stuff is polystyrene, which I think is R-5 per inch, it would be about R-60, right? Since there is no framing members, no thermal bridge, you would just need to worry about the air sealing and thermal bridging of penetrations like doors and windows.
It was my impression after watching a television show on prefab houses about 5 years ago, Build one place, ship somewhere else and assemble. The show I was watching explained how instead of using nails and screws, attaching components with adhesives were used instead to speed up the process. I thought it was fascinating. I thought they used SIPs in the construction.