This "double-envelope" house design was very popular for a while maybe 15
years ago. I think I even have a book on the system somewhere gathering
dust. There were a number of problems in my estimation. First, as the late
Bill Yanda once noted, even though the designers could figure out which way
the air-flow arrows went, the buildings often could not. In some of the
monitored houses, air failed to circulate as designed and thus did not
distribute heat properly. Second, there was a significant potential for
mold growth in the cold lower portion of the loop. This could result in
health problems in the house (as could rock heat-storage beds under
houses). Third, for the money, materials, and space devoted to the envelope
(which was often a foot thick in cross-section), it simply wasn't worth it.
It is smarter to invest in better windows, higher insulation levels,
especially with the advances in glazing technology made since then.
While this design was fun to argue about, the double-envelope design is
almost certainly obsolete.
Alex Wilson
Environmental Building News
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