Zero-energy buildings: We have the technology


Earlier this week, I talked to Kent Peterson, past president of the American Society of Heating, Refrigerating and Air Conditioning Engineers. This was a lot more exciting that it may sound. ASHRAE standards on energy efficiency end up written into our building codes, which means the organization plays a big role in influencing the shape of energy policy in this country. I talked to Peterson to find out whether zero net energy buildings—buildings that produce as much (or more) energy as they use—were really a practical goal. His answer might surprise you.

"We have studies that show [zero-energy buildings] are practical for approximately 62% of buildings in the U.S., based on technologies we have today," he said. "That's mostly one and two-story buildings and still leaves out a lot that can't reach it, but those buildings can be low energy.

In fact, Peterson said that currently available energy efficiency technologies alone (not even looking at generating power from wind or solar sources) could reduce the amount of energy used by the total U.S. building stock by 50%.

The catch: Hitting that 50% energy reduction goal—let alone getting to zero-energy buildings—means more than buying a better boiler. The environmental systems in buildings—the lighting, heating, cooling, etc—are already pretty efficient, Peterson says. When your heating system is 80% efficient, you can't get a 50% reduction in overall energy use by focusing on squeezing out the last few drops there. Instead, Peterson says we have to put more thought into reducing "plug load"—a fancy way of talking about all the gadgets and appliances we plug into sockets.

Think of all the stuff you leave plugged in all day. Like the microwave. It's nice having that clock function, and it really doesn't take much energy to run. But over the course of a year, all the electricity you used to run that microwave clock ends up being enough to power 30 hours of microwave cooking time, Peterson says. All the little "phantom" draws add up, and they bite us hard.

Automation is the muzzle. I've gotten pretty good about remembering to shut lights off in rooms nobody's using, but expecting me (and millions of Americans like me) to thoughtfully and correctly power down every electronic device they aren't using even half the time is about as unrealistic as expecting Anna Karenina to become the movie blockbuster of the summer. Instead, we can rely on "set it and forget it" systems that turn off unused devices while we're at work or asleep based on timers or occupancy sensors. Peterson already has something like this in his house.

"It's just controlled by my computer in my house, and it cuts power to specific outlets either by timer or click of a button. So I can cut power to my TV overnight, and automatically reduce phantom loads. That system had a bigger impact on my home energy use than all my other energy saving projects combined."

Image courtesy Flickr user Rennett Stowe, via CC