I also read a book on envelope houses. Basically it's a house built inside an earth sheltered structure, with a solarium for heat gain and a basement area for heat storage. They did a huge study of homes that were built in the 70's, and their positives and negatives. Most of the homes used LOTS of glass, which meant large temperature swings and lots of heat loss at night. It seems like a good idea, but my conclusion is that it is not as good as a super insulated earth buffered home with properly sized windows.
I toured an earth sheltered house in Platteville, Wisconsin. It was really neat. It used the fireplace for primary heat, and when coupled with the large south facing windows, it did very well. The problem with all the windows was lots of sun year round, looking back, they wish they would have built an awning over the windows. The house had "heat exchanger/heat pump" for ventilation. It was two 300' sections of black tube , one inside the other. The tube was snaked under ground where there had been excavation, and ventilated near the house. Air was pulled into the house through one tube (and released through the other). Air temps entering the house were the same temperature as the house, and temps leaving were at the same temp as the outdoors. I will have to read the article that was done on it, and see if I can sight a source where people could get the article on it.
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