This NY Times article about "passive houses" is very intriguing, especially considering all the crazy ice storms and power outages lately all over.

Growing in popularity in Germany and Scandinavia, "passive homes" are heavily insulated, tightly sealed homes which don't require active heating, even in the coldest German winters. Passive heating from the sun or the household appliances or even body heat will be enough to keep the house warm.

One trick is ventilation. But changing the air usually means loss of heat, but the use of a heat exchanger can reclaim that heat when drawing in fresh, cold air from outside.