"To date, Passive House Institute-U.S. has educated about 160 builders, architects and engineers in the standard through a series of training programs and a final certification exam. By year-end, the number is expected to be 300, and Ms. Klingenberg said the institute was having difficulty meeting demand for its courses. But this sort of building comes at a premium, particularly in the United States, where the fledgling movement is trying to ramp up from scratch and has to rely on products supplied by a market that is geared toward less rigorous programs."