enlarge Courtesy Kaplan Thompson Architects

Solar panels on the roof of Keith and Mary Collins’ office-studio in Rockport are expected to provide all the energy the building needs.

enlarge Courtesy Kaplan Thompson Architects

Each wall, floor and ceiling panel of the 42-by-18-foot Rockport building has an insulating value of R-40, roughly twice a typical wall cavity in a new Maine home.

enlarge Courtesy Kaplan Thompson Architects

Keith and Mary Collins' new office-studio in Rockport is a prototype building constructed of prefabricated 4-foot modules. It will be heated primarily by solar panels on the roof.

TO LEARN more visit www.brightbuiltbarn.com

If visitors notice green lights glowing from the base of Keith and Mary Collins' new office-studio in Rockport, they shouldn't be concerned. They're a real-time indicator that solar panels on the roof are producing more power than the building needs, and sending the excess electricity into the regional grid.

The glowing "light skirt" is a graphic way to call attention to a building that's engineered to generate more power over the year than it consumes – a "net zero" or "zero energy" design, as architects say. The project is among the first of its kind in Maine.

This demonstration project has another unusual element: It's made from prefabricated 4-foot modules already packed with electrical wires and plumbing. The panels were trucked from a factory in New Hampshire to Rockport and assembled in three days during July.

The structure is so well insulated that the couple is expecting to keep warm this winter with only sunshine and a small fan blowing across the warm coils of a ventilation unit.

But this 700-square-foot prototype, called BrightBuilt Barn, isn't really about an office-studio. The wider goal is to use the building techniques to create reasonably priced, easy-to-assemble homes that use a fraction of the energy of conventional housing.

These homes could become available for sale next year. The creators are trying to get the price down to about $200,000, minus land and installation of utilities.

"There's really nothing out there now that does what this does and is relatively affordable," said Phil Kaplan of Kaplan Thompson Architects in Portland. "Especially in this climate, we think this is something people are going to be excited about."

Kaplan's firm is the lead architect on the BrightBuilt Barn project, which is a collaboration between a handful of Maine sustainable design professionals and Bensonwood Homes of Walpole, N.H., a pioneer in modern timberframe and panelized construction.

The interior of the building, which includes a bathroom, kitchen, artist studio and office, is currently being finished to suit the Collinses. They plan to occupy the space this fall, following a ribbon-cutting in October.

Kaplan and Bensonwood are still tweaking the design, and expect to learn more about the building's performance this winter. But BrightBuilt Barn already is drawing interest from real estate developers, who see it as a good fit for the second-home market, specifically for waterfront and island locations.

Keith Collins didn't set out two years ago to create a zero-energy building. He and his wife needed more room and decided to either renovate their Rockport house or build a detached barn. Collins, who says he maintains "nerdy interests" in climate change and other issues, contacted Kaplan, who was expanding into green architecture. What evolved was an experiment in sustainable living and energy efficiency.

"We wanted to do something that was in reach of the average person, using off-the-shelf technologies in a creative way," Collins said.

Collins and Kaplan declined to say how much the 42-by-18-foot building costs. There were research and development expenses for the prototype.

Working with Bensonwood and others, this is what they settled on:

Each wall, floor and ceiling panel has an insulating value of R-40, roughly twice a typical wall cavity in a new Maine home.

Triple-glazed, gas-filled windows are supplemented by translucent glazing made of polycarbonate and a patented gel that blocks heat loss but admits light.

Solar panels on the south-facing roof generate electricity and heat water.

A heat recovery ventilation unit maintains air quality in the tight structure. It also will provide supplemental space heat.

These features and a host of efficient building techniques are expected to earn the building a top platinum rating from Leadership in Energy and Environmental Design, a program...