It may be a relatively novel concept in the US but in Europe it has been around for a while. Those passive houses really work. If you do the maths right and know how to improvise, building a passive house is actually much cheaper than conventional construction. I know a family who built their own passive home almost entirely out of natural, locally available materials (mostly wood and mud) for very little $ and it's a pretty comfortable place to live. A friend of mine has started a similar project. We'll see how it turns out.