We’re planning to build a house in about a year and are just beginning to talk with architects about the design. It will be a small house (<2000 sq. ft), but we want it to be extremely energy efficient, with walls at least R-30 and possibly more. Cost is an issue – we need to get the most bang for the buck.
One architect suggests a double wall construction that will result in R-50 walls. Other people have told me that’s an antiquated practice and SIP’s are much better. And then of course there are those who love ICF’s. Assuming that they can all provide the same R-50 (is that a valid assumption?), which one is the most cost effective method? Any and all comments are appreciated.
Replies
Just chasing R-value is a bit of a fool's errand, be/c it's an incomplete measure of the energy effectiveness of a house. Not all insulations perform the same, even when having ostensibly the same R rating. Another factor will be the air tightness, as measured through air changes per hour. With some methods, you get additional benefits, such as a reduction of sound transmission, stability in the face of wind loads or earthquakes, etc.
And there you have it folks.... Such a concise answer this thread is now complete!;)Really - anything else is fluff and details.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I will not offer theory, just experience, hope it helps.
I am in an ICF house - it went up faster than I framed my last (bigger) house. It is very comfortable, quiet, and the heating bills are extremely low. After this, I would not want any other form of construction. The train goes by (pretty close) and we barely hear it, the wind blows and we are basically unaware.
We put in Anderson 400 series windows, and blown fiberglass (compromi$e) to R50 in the attic (truss const) The walls are better, imho, than R50 fiberglass walls b/c of the lack of air infiltration issues.
My feeling is that the ICF walls are such good insulation, other measures to be efficient are almost insignificant in comparison; I'd rather have spray-foamed the lid, but I don't think it would have made a lot of difference in the overall picture. I had a geothermal heating system in my last house, this one uses (very little) oil for heat.
The house came in at $65 s.f. (my cost - there are some built ins, custom-level trim, nicer materials etc) to build, and the s.f. figure doesn't include the 1900 s.f. basement, which will be nice some day. I am sold on ICFs, but I haven't done SIPs or super, and your mileage may vary.