BOULDER, Colo. - What it means to be zero energy:
Ultimately, a zero-energy home should create as much electricity as it uses over a year.
Often, that means that the house is producing far more electricity than it uses in the summer when the sun is strong and high in the sky and feeding that excess to the grid. In the winter, zero-energy houses will often pull that credited energy back off the grid to make up for the shorter days and lower sun rays.
When a house is marketed as zero-energy, it means that the house is designed to meet the energy demands of an average occupant. Of course, if the homeowner leaves the windows open all winter, or leaves the lights on all the time, they could exceed the amount of energy the house produces. To really say a house is performing at zero energy, it takes looking at a year's worth of energy bills.
Local developer Ron Monahan stood outside the first of 12 homes he and his business partner plan to build in a new north Boulder subdivision and talked about his vision: "We're bringing this to the masses."
"This" is a zero-energy home. It's a house built with less lumber and more insulation; with recycled countertops and bamboo cabinets; with a geothermal system and a 10-kilowatt solar array. And it's built in what will become the first zero-energy neighborhood in Boulder, and likely, one of the first in the country.
Monahan and co-developer Terry Britton worked with architect George Watt and Silver Lining builders to construct the model home for the planned SpringLeaf "eco-community," which will sit across Broadway form Lucky's Market.
The systems installed in the nearly 4,000-square-foot house are designed to create more energy than the average homeowner will use over a year - but it's also designed to be easily replicated at SpringLeaf and on other lots in Boulder, which the developers say will bring down the cost of building zero-energy homes.
"We're bringing this to the marketplace, and we can deliver it at a good price point," Monahan said.
Monahan and Britton expect to sell the model home for somewhere in the neighborhood of $1.2 million, which would break down to just more than $300 a square foot. But they believe they can drive the cost down to below $200 a square foot for the other zero-energy homes, five of which will be single-family houses and six of which will be smaller, attached townhouses.
Just a few years ago, zero-energy homes were mostly the purview of passionate tinkerers - green builders, sustainably minded architects and renewable-energy gurus who often worked on their own homes, wiring the photovoltaic systems and hooking up solar thermal water heaters on their own.
But more recently, zero-energy homes in Boulder have popped up in the luxury market, with some costing around $600 to $800 a square foot.
Scott Rodwin, a Boulder architect specializing in "deep green" building, said the lessons learned from building zero-energy homes at the upper end will help make those technologies accessible to the average homeowner.
"The upper end has the resources to break ground for the rest of us," said Rodwin, whose firm designed the Edge House, a zero-energy home that achieved the U.S. Green Building Council's highest eco-friendly certification - the Leadership in Energy and Environmental Design, or LEED, platinum designation.
For example, Rodwin's Edge House is the first home in Boulder to ever get permission from the city to install a graywater system, which uses treated water form the sinks and showers to flush the toilets. Rodwin was able to spend time and money working with the city to get the system permitted because the homeowners had the financial resources available. The next graywater system installed in the city will now be able to follow an existing protocol, saving money on permitting costs.
"The houses that have the larger budgets are really able to push the envelope of how far you can go to build green," Rodwin said.
The SpringLeaf project's success at lowering the cost of a zero-energy home is also based in part on the collective wisdom earned by Boulder's progressive green building community.
"That's really the lessons learned over a long period of time," said Watt, SpringLeaf's architect. "You work with the early adopters, sort of the avant-garde, and you learn from it. We took what we learned over the last 10 years and brought it to bear here."
And one of those lessons is that simple is better, Watt said, both for the homeowner who may not have any predisposition toward tinkering, but also for the cost of the project. SpringLeaf's houses, for example, will be all electric. The houses are not designed to have any solar thermal water heating equipment, and natural gas is not used. Instead, the appliances are electric and the heating and cooling system is a based on a geothermal electric heat pump, which leverages the earth's stable below-surface temperatures to keep the house comfortable.
The result is a remarkably uncomplicated utility room in the house that lacks the usual nest of tubes, valves and wires.
The overall plan for the neighborhood was also designed with solar access in mind, allowing the photovoltaic panels that power the house to work at maximum efficiency.
"The whole idea was to integrate the systems into the buildings," Watt said, "and the buildings into the neighborhood."