I had a guy I went to high school with that was an architect who became a home builder in the late 70s.
He built some wonderful traditional homes in upscale neighborhoods that had some very innovative passive solar coupled with energy recovery systems for the HVAC systems. These homes would use 30% of a regular home in the winter and only 50% in the summer which was a 3 month season in that area.
He sold a dozen but at that time energy was so inexpensive that there was not a good demand for him to stay in the business. At that time the pay-back for the extra cost took 2/3rds of the mortgage life. Now with the higher energy costs, they probably pay back in eight years the initial premium.
One of the features he included were wonderful stone Trombe Walls.
See here for a trombe wall description —
http://en.wikipedia.org/wiki/Trombe_wall
The passive solar house that I almost bought back in 2005 (posted the Zillow listing for it on this thread) had a Trombé Wall, I’d just forgotten the name. South-facing wall of windows, a sort of tall atrium or greenhouse effect, with a masonry wall inside the glass. This house had usable square footage between the two, I’m recalling about six feet. Owners were using it as a sort of hanging greenhouse, growing vegetables out of season, floor was stone. A large stand of native oak blocked the sun in summertime. Interior openings with shutters in the masonry interior wall were used to further regulate heat gain or loss for comfort in the main residence. There was a vent in the peak of the gable that could be opened or closed to release or retain heat also. It was an unusual house and an unusually nice one, I suspect I’d have been happy with it.
2/3 of the mortgage life, payback is what I would consider VERY expensive passive solar.