On a cold, sunny day last week, the wind whipped across a Bucksport construction site, rippling a man-made pond and causing blue tarps to billow in the unfinished garage of Michelle Atherton’s future home. The previous night, a gust had blown a piece of scaffolding through the roof.

Indoors, however, things were calm, quiet and surprisingly warm, given the wind and the fact that the heating system had yet to be turned on. Another surprise were the walls, which looked more like the inside of a Styrofoam cooler than the inside of a house.

But this is no ordinary house. Atherton and her husband, Mike, sought maximum energy efficiency when they designed it, and everything from the wood-burning furnace in the basement to the giant solar panels outside were chosen with that in mind. So, too, were the exterior walls, crafted of insulating concrete forms, or ICF, which consist of stacked, Lego-like blocks of reinforced Styrofoam that are filled with concrete.

Atherton, 36, jokingly refers to the material as “coffee cups and concrete.” But these blocks are so strong and efficient that Atherton has used them to build not only a home, but her business, New Form Building Systems of Bucksport.

She and her friend and business partner, Erica Atherton Libby, 33, are both engineers – Atherton earned her civil engineering degree from the University of Massachusetts at Lowell, while Libby studied chemical engineering at the University of Maine. They’re also both stay-at-home moms who wanted jobs that would allow them flexibility.

“A traditional engineering job usually takes 60 to 70 hours a week,” Libby said. “You can do it [work and raise a family] but we don’t want to do it with young kids at home.”

They found their opportunity when Mike Atherton – also a civil engineer – discovered ICF. After researching all of the building materials on the market, Mike liked ICF so much, he agreed to be the local distributor for Amvic, the Canadian company he chose. Oh, and he signed Michelle on to run the business. She promptly went to see Libby, who happens to be her husband’s niece.

“I was lamenting, ‘Can you believe this, Erica?'” Michelle said, laughing. “Then I said, ‘Would you like to do this with me?'”

“So here we are,” Libby added. “We juggle the kids between us and get things done.”

That was a year ago. They have since switched to a Massachusetts-based ICF manufacturer called BuildBlock, which offers a product that is equal in quality but with lower transport costs. They also have used the Athertons’ home to experiment with new materials and techniques.

“Our house is to try things out and see how things go,” Michelle Atherton said. “That way, we can speak intelligently to our customers about what worked for us and what didn’t.”

Though ICFs have traditionally been used for foundations, they’ve become the fastest-growing alternative to wood-frame structures for above-grade construction, according to the Illinois-based Portland Cement Association. In 2004, about 60,000 single-family homes were built using ICF in the United States.

The ICF Association attributes the rise in popularity to the decline in American lumber quality since the early 1990s, but Atherton had other, more timely reasons for choosing the material.

“It’s definitely a conscious decision,” she said. “We decided we needed to make sure our structure was energy-efficient, too. When we made the commitment to be solar we made the commitment to be energy-efficient as well.”

ICF is among the most efficient building materials on the market today. The polystyrene sheathing has a high insulation value. The concrete holds temperature so well, that if Atherton’s furnace were to break down, no one would notice for days. And the nature of poured concrete cuts down on drafts.

“You save 50 percent on your heating oil costs,” Libby said. “It deadens sound by 75 percent, which is great if you live near an airport, a busy road, or if you want music rooms for your kids.”

“Or if you have teenagers,” Atherton added wryly.

The material also contains no formaldehyde, HCFCs (hydrochlorofluorocarbons), asbestos or fiberglass. Though many building materials and finishes can release chemicals into the home over time, ICFs won’t. They will, however, add 3 percent to 5 percent to upfront construction costs.

“We tell our customers where you want to put your money is your walls and windows,” Atherton said. “That’s where you’re going to really get your energy efficiency. As much as you can afford.”

“You can worry about your granite countertops or your ceramic tile floors later,” Libby added.

As mothers – Atherton has a 2-year-old and a 2-month-old, both daughters, and Libby has a 5-year-old son and a 2-year-old daughter – they’re clearly thinking about the future. But so are some of their clients, who are building ICF homes in Bristol, Bucksport, Eddington, Carmel, Buxton and Lamoine.

For the last five years, local builder Dean Hoke has used ICFs from Hammond Lumber and Granville Lumber for foundations. He’s now working with New Form Building Systems to build his first full ICF house in Bucksport.

“They’re easy to work with and you can use them in any weather, and it gives me just a little bit more control over the building process,” Hoke said.

His clients like ICFs because they produce a stronger, weathertight structure – in the South, homes built of ICF weathered last fall’s hurricane season much better than their timber-frame neighbors.

“They make a real nice, energy-efficient house that heats very easily,” Hoke said.

Heat and ease of construction are only part of the appeal for Atherton and Libby. They also find their “home work” a nice respite from other responsibilities.

“It’s nice because it gives you the mental break from, at the moment, potty training,” Atherton said, laughing. “This is a good opportunity for us to use the skills we learned in school while raising a family at home.”

New Form Building Systems will hold a free ICF installation training seminar from 9 a.m. to 3 p.m. Feb. 9 at Jeff’s Catering in Brewer. To register, call 469-2711, 949-5706 or e-mail info@newformbuilding.com. For more information on ICFs, visit www.newformbuilding.com or www.icfweb.com. Kristen Andresen can be reached at 990-8287 and kandresen@bangordailynews.net.