Although you won't find a ratings sticker on the front door, a new house for sale in Still River proudly boasts a Tier II designation from the Energy Star Home program, the program on which the Harvard's soon-to-be enacted Stretch Energy Building Code was based.

The four-bedroom, two-and-a-half bath, modern colonial at the south end of Still River Road sits on five acres looking west over the Still River valley area. Design/builder Carl Warren of Warren Design Build of Berlin writes that the new home "will use up to 70 percent less energy and fuel costs than a traditional system for this size home."

Building an energy-efficient house was not a stretch for Warren. Drawing on recent energy advancements, guidelines from the federal Home Energy Star Program, and his 30-year building experience, Warren built the 3,457-square-foot house with careful attention to the basics of modern energy-efficient building: a tight thermal envelope, controlled ventilation, energy efficient doors and windows, high-efficiency heating, and Energy Star appliances and lighting.

Warren used 2-inch isocyanurate rigid foam on the exterior walls and roof sheathing, essentially creating a foam box around the house. According to Warren, this "thermos bottle" effect also keeps moisture from condensing on the inside surface of the exterior HardiPlank fiber cement siding. Inside insulation includes 3.5-inch insulation on the inside of exterior walls and 9.5-inch insulation on the inside of the roofs. Meticulous caulking and foam sealing where exterior elements come together prevent unintended air leaks and complete the thermal barrier.

Further heat loss is limited by high-performance windows, in this case, Harvey Double Low E, Krypton filled, triple-glazed windows with an R5 performance rating.

According to Warren's description, most of the home's energy savings comes from its air-tight construction. "A 2010 Code built home that is reasonably well insulated and sealed has about .5 air changes per hour, and a total air change every 2 hours. Our result was .16 air changes per hour, with a total air change every 6.25 hours."

A tight building requires less heating capacity from the HVAC system. Warren installed a Munchkin propane-fired condensing boiler and a First Company air handler on the upper floor. A Fujitsu air source heat pump with supplemental baseboard heat warms the first floor, while radiant floor heat with water from the boiler supplies the unfinished basement.

An impenetrable exterior envelope—as well as modern building codes—requires healthy ventilation. In addition to the outside air supply in each of the fuel-burning appliances, an Imperial heat recovery ventilator exhausts air from the bathrooms and distributes pre-heated fresh air back to the other living spaces.

Warren plans to add a solar thermal system for hot water and to preheat water for the boiler system. This addition, along with his use of some recycled materials and careful onsite materials handling and recycling during construction, have prequalified the house for the highest Energy Star Home rating, Tier III.

Warren, along with Sara, his wife and building partner, credit the Northeast Sustainable Energy Association (NESEA), Building Science Corporation, and Consumer Services Group with providing them invaluable information about green building practices and materials.

Much ado was made about the Stretch Energy Code the town passed at the Special Town Meeting last November. Predictions of inflated costs and impoverished builders were contrasted to toasty homeowners with reduced fuel costs. If the Still River House had been built under the new energy code that will go into effect July 1, it would have had to meet a Home Energy Star Ratings System (HERS) index of 65, meaning that it was expected to use 65 percent as much energy as a home built to the 2006 building code. Warren's house rated a HERS index of 47 when measured by a blower door test and a thermal bypass checklist, qualifying it for the Tier II rating and showing what a tight envelop can achieve.

While Warren's house surpasses the Stretch Code's energy efficiency requirements, its achievements through the use of advanced building techniques, high-efficiency materials, and energy-efficient HVAC systems may become not the exception but the expectation for new home construction.

Warren's Energy Star Home is currently on the market for $859,000.

Energy Star home at 304B Still River Road, Harvard. (Courtesy photo)