Last night I was at a Passive House meetup in Chicago where among many other things, I learned about Energisprong. (For those new to Passive House, it is a method—and a philosophy—for designing super efficient buildings.) Energiesprong, which came out of the Netherlands (hence the quirky-fun word), is extreme-retrofitting. As the slightly Monty Python/Terry Gilliam-ish animation above explains, older homes get new, better-insulated facades, solar roofs and system upgrades. The kicker is that the work is completed in about a week. Energiesprong is catching on in Europe. Here in the US, Rocky Mountain Institute's REALIZE initiative is working out the logistics to make this practical at scale.