LAWRENCE - With its huge "Think Green, Live Green" banner and its blocks-long mass of space being converted into "ecoluxury" residential and commercial space, Monarch on the Merrimack is the grandest example of this city's plan to go green.

But while the developer of the former Wood Mill has paused to
arrange new financing, a much more modest project - a three-bedroom, 2-bath home built in pieces in a factory and assembled onsite in less than a day - opens to the public today just around the corner.

It is the latest output from PowerHouse Enterprises, a Lawrence company out to extend the conventions of "eco-friendly" to include economical as well as ecological aspects.

PowerHouse won the right to build on a vacant urban dumping ground, in part, by agreeing to the city's requirement that the property meet Leadership in Energy and Environmental Design standards established by the US Green Building Council. Michael Sweeney, the city's planning director, said he believes Lawrence is the only Massachusetts community with such an initiative.

PowerHouse hopes the house will achieve LEED's highest rating,
platinum. Two units it designed in Cambridge were among the first 15 residences nationwide to win that designation.

From its preformed foundation to a pergola re-formed from shipping pallets that will shade the house in summer and allow light in during winter, every design decision by PowerHouse founder and president Quincy Vale and design principal John Rossi about organization, materials, and finishes, both inside and out were made at the junctures of resource efficiency, health, and affordability.

"Overall, green is good, but the things that work are health and money. Unless homeowners save money from their investment, I'm not sure it's going to sell," Vale said.

Perhaps most remarkable is that Vale and Rossi built this house at a cost of about $165 per square foot. The 1,500-square-foot house with another 400 square feet of finishable space in the basement is on the market for $324,000.

"On the face of it, sight unseen, the construction cost is extraordinary, very admirable," said Paul Eldrenkamp, owner of Byggmeister Inc., a Newton remodeling company that focuses on high performance construction. Typically, he said, LEED platinum implies high-end work, and therefore high-end cost. "You're probably not putting up sloppy trim or cheap flooring" in a LEED platinum project, he said. "That number is surprisingly low."

Vale said that the house's economy will go well beyond price. PowerHouse has calculated that in sewer and water fees alone, the homeowner will save about $450 annually versus comparable, traditionally built housing. The house has dual-flush toilets, low-flow showerheads, and a high-efficiency dishwasher, but those elements are really secondary players in this story.

"The big gains in energy efficiency are in design. Anyone can stick energy-efficient gizmos on a house, but a lot of times, it's putting lipstick on a pig," said Vale, who is armed with a family background in manufacturing, graduate degrees in law and business, and a desire to help change the world.

The house has only 7 feet of hallway, 3 percent of the total space, compared with 12 percent to 15 percent of circulation space in a typical home. "You don't live in the hallways," Vale said. It's space homeowners won't have to heat, carpet, or maintain.

That scant space contributes strongly, both to the home's efficiency and its style, Vale said. Central air conditioning was left out, for example, because the stairwell will funnel hot air upward, where windows placed for cross ventilation can vent it to the outside.

Rossi rhapsodizes over the windows, which pair casement and awning styles. Between the first and second floors, they combine to cover a space 6 feet by almost 8 feet, which allows light to flood into both floors as well on as the stairs.

"If you love houses and architecture, you have to love these windows," said Rossi, a vital, trim architect born into a family of Connecticut stone masons. "It's great to be able to open the windows and listen to the rain. It's a little romance at no extra charge."

Vale and Rossi clearly have a place for romance in their building plans, so long as it doesn't lure them too far from the goals of efficiency. The flooring in the living room, for example, came from an old Lawrence mill.

"You don't do an antique wood floor because it's cheap. This was reasonably priced, but it's mostly an aesthetic choice," Rossi said.

The cladding on the outside of the house as well has clever, subtle design elements. Part of it is wood, but vertically ridged metal siding adorns different sections, at different elevations. Yes, it's an aluminum alloy with at least 30 percent recycled content, according to Vale, but it also knits the building into its surroundings, relating to siding on the power plant just across the train tracks that once served the Wood Mill.

The south-facing roof has a dramatic pitch, determined with the proper angle for solar power or hot-water apparatus. Those extras, however, have been left to the homeowner to purchase and install, if desired. The builders also designed a niche where the owners could install a gas stove insert.

The Cambridge duplex, which PowerHouse designed but did not build, does have many of the extras, such as radiant-floor heating, as well as mod-cons to be expected to new homes: in-wall wiring for surround-sound speakers and accommodation for a flat-screen television.

The homes were manufactured by Epoch Corp. of Pembroke, N.H., which builds anywhere from 100 to 160 houses a year. Its chief executive, John Ela, said PowerHouse's approach let Epoch try several techniques, such as using icynene spray foam insulation, that it has since incorporated into its standard offerings. He lauded PowerHouse's "very practical approach. They keep focused on the goal of the design and are willing to be flexible to finding the best solution," Ela said.

Vale, who developed and managed the Green Buildings Program for the Massachusetts Technology Collaborative before becoming a developer, has grander visions for where to take that approach.

He said that in a project such as the Lawrence house, many of the materials are special orders, such as Forest Stewardship Council-certified wood or even the cabinetry, which comes from Ikea, which isn't set up for wholesale supply.

He has dreams of opening a PowerHouse factory, where houses can be built most tightly, out of the elements, and where castoff materials could be routinely "reduced, recycled, or reused," a mantra of the green set.

"I'm beginning to develop the notion that a house can't be very green unless it's modular or prefab," Vale said, pointing out that in some countries, half the homes are factory-built.

He added that building whole neighborhoods of homes at one clip would drive green-construction costs down even further by standardizing specialized materials and achieving other economies of scale. But none of those would be the biggest prize, Vale said.

"On a wider produced scale, this can have a really big impact. . . .
Our houses use 30 percent of the energy, so you're cutting 70 percent of your carbon output."