It’s probably a safe bet to assume you’ve never been in or even passed by a zero energy building. The U.S. Department of Energy lists only eight zero energy buildings in the U.S. on its high performance building database (though there are a few others scattered across the U.S.). A number of developers, such as Meritage Homes, have started building zero energy developments around the U.S. In Europe, the Passivhaus standard has been used to build over 40,000 residential and commercial buildings, and the city of Frankfurt, Germany requires it in construction of new public buildings. Still, these represent only a tiny fraction of the total building stock and, for most of the construction world, zero energy design represents an all but unattainable challenge given the up-front costs of deep energy efficiency and renewable energy systems. Zero energy building, however, is expected to increase dramatically in the construction industry in the next few decades as a set of regulations around the world come into effect. As soon as 2016, the United Kingdom will require zero carbon construction for all residential buildings. Newly constructed dwellings will need to achieve deep levels of energy efficiency (45-60 percent lower than a comparable building built in 2006). That’s just four years away.