Proceed with Caution on Net-Zero Homes

You'd be forgiven for being skeptical of developer claims, given the leading role they played in history's most spectacular crash in home values. So what about the small but growing chorus promising zero-energy homes that sell for a premium?

If it were that easy to build and maintain homes that produce no carbon output but are still comfy, wouldn't the recent climate summit in Copenhagen have gone a lot more smoothly? And more to the point for would-be buyers, how much faith can you put in a claim that the house in question performs a technological miracle?

The truth is that technology exists to make affordable, pleasurable homes that emit almost no carbon. But the technology is not yet widely available or tested, so homes that claim to produce zero-energy may be relying on a lot of gimmicks.

The claim of "zero-energy" got the attention recently of the Wall Street Journal (house organ of the noted greenie Rupert Murdoch), which reported credulously about a handful of such projects, from Greenfield, Mass. (heh, heh), to Berkeley, Calif. (surprise, surprise), to -- wait for it -- Green Valley, Arizona.

Buildings are a huge source of CO2, and net-zero buildings that produce their own power from renewable sources, add nothing to the atmosphere's carbon levels and cost almost nothing to heat and cool would undeniably be great.

But this is very much still a show-me case: the projects have to deliver as promised to become economic or ecological models.

You'll notice that a lot of these are developments built from the ground up with their own spanking-new infrastructure. Even so, they only run as efficiently as the larger systems that feed them. Some electric utilities have trouble connecting to super-efficient on-site power: indeed, these on-site power generators can jam up a bigger electric networks by feeding it more electricity than its transformers can handle.

However, most zero-energy projections presume that nothing goes wrong in the links to the local electric or steam grid -- and that's a big assumption. It's telling that the utility manager quoted in the Journal article says his company is backing the net-zero project as a way of relieving the grid's burden to service new homes. When your local utility is gasping for breath -- as many of the regional systems that make up the nation's aging electrical grid are -- you shouldn't necessarily expect a smooth ride in your new home.

Moreover, most of us live in buildings that are already in place. It's a lot harder to adapt the latest green technology to existing buildings.

So, instead of looking for the Holy Grail of zero-net emissions, today's smart buyer looks for signs that a building will be as airtight and efficient as possible. When you know your building isn't sending out drafts or and you're not blasting the A/C while no one's home, you know you're using every cent you pay for in heat, air-conditioning and hot water.

How do you move closer to zero-waste? Two ways: through a rigorous engineering method called Passivhaus (like many progressive home-energy ideas, it comes from northern Europe, like the model from Germany pictured above) and through enforcing and rewarding good habits.

Homes emit energy through their walls and windows. If those are sealed tightly enough, single family homes and even mid-rise towers need minimal heat or air conditioning. A nonprofit project in Syracuse is building one such home, with a frame made of airtight materials. it is being sold for less than $150,000. If the technology works, the hope is it will spread in its devastated Syracuse neighborhood and beyond. A similar project is underway in Brooklyn, in an experimental "co-housing" building where occupants share kitchens and other life basics.

Aside from being the beneficiary of one of these nonprofit projects, the most reliable way to control how much carbon you spew is to control what you do with your house. It costs a lot of money to load a house with rare engineering or experimental technologies. But it costs almost nothing to change your behavior.

Motivations to change behavior, says Jonathan Rose, the developer behind green developments such as the Metro Green complex in Stamford, CT, deliver the most reliable energy savings for now. A future luxury development in California, Sonoma Mountain Village, also projects saving 1.8 tons of greenhouse gas per person through better behavior.

So, yes, zero-energy is coming, perhaps even to your area, in the near future. But do your homework. if a developers wants to sells you a turnkey home in a new subdivision that claims to consume zero energy, proceed with caution.
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