Leave it to Germany to create Passivhaus, an extremely rigorous standard for home energy efficiency that makes houses so efficient that they can take on a German winter with nothing more than the heat from a hair dryer.

The Passivhaus system uses technologies that are available today, and there are over 20,000 Passivhaus homes in the world (though, only about 7 in the U.S.) The standards require a good mix of high-tech (heat-exchange ventilators and fancy triple-pained windows) and low-tech (big thick, well-insulated walls.)

Of course, all of this makes the homes difficult (and expensive) to build. The hardest part is making the homes nearly airtight. The foundation walls and ceiling all have to seal together perfectly. In effect, a Passivhaus home could almost exist on the surface of Mars. Making them air-tight also means they need special ventilators that pump in fresh air without pumping out the home's heat. These heat-exchange ventilators are becoming fairly common, I've even got one in my house, though it's not nearly as air-tight as a Passivhaus home.

All of this adds up to a home that can be as much as double the cost per square foot of your average American home. Of course, we're talking about current average American homes, which, we all must admit, haven't been the most well-built buildings in the world.

In the end, Passivhaus blows even LEED Platinum out of the water, requiring 70% less energy for heating than a LEED certified home. Most days of the year, you can literally heat your home with body heat...if you play enough DDR.

The Wall Street Journal offered an intriguing challenge to four top architectural firms -- Mouzon Design House, Rios Clementi Hale Studios, Cook + Fox, and William McDonough + Parnters -- design the green house of the future. The teams cooked up some intriguing designs full of eye-catching concept art and all the right hot topics -- solar power, heat pumps, carbon nanotubes and more.

So why are some environmentalists complaining about the competition and the concept of a "green suburbia"?

Roger Lewis of the Washington Post offers an intelligent and considered rebuttal to the WSJ piece, writing, "Focusing on hypothetical designs of free-standing houses can even be a distraction. It can mask a more serious aspect of the challenge: the diminished sustainability of low-density, residential subdivisions in suburbia where most free-standing houses of the future are likely to be situated."

He states, "No matter how green individual homes are, suburban sprawl is intrinsically anti-green. It generates infrastructure inefficiency; car dependency and rising fossil fuel demand; carbon-emitting, time-wasting road congestion; and, despite availability of inexpensive land at ever-greater distances from jobs, escalating development, construction and public service costs."

The article provides an intriguing reminder that green architecture isn't always as green as it seems. And cities, often associated with pollution, are potentially the greenest societal direction of them all.

Here at Ecogeek we often cover green architecture and building technology, both in the city setting and in suburbia. As there will always be some people who yearn for suburban or rural settings, both design approaches have merit. However, when it comes to the greater good, or greater green perhaps, cities arguably present the most environmentally friendly, lowest impact, living opportunity.

From electric vehicles to urban agriculture, the city has arguably the greater potential for green communities, with minimum land use, greatest energy efficiency, and lowest environmental impact. And with the U.S. population's exodus from cities to surburbia reversing for the first time in five decades, the timing is ideal for green city architecture. So let's move the focus onto greening cities, but let's not blindly throw out suburban efforts wholesale, either.