mosellegreen:

“There’s a thousand and one things in the houses that are like that,” he says. “You’d never see them, the construction techniques, but the house is filled with them. Construction techniques that make the house not just less expensive, but actually makes it perform better than they normally would.”

One problem is that regulations haven’t caught up with the technology, so they often can’t get permits to do the building.

This House Costs Just $20,000—But It’s Nicer Than Yours