Everybody loves energy-efficient homes. Ask home builders or home buyers if they want energy efficiency and most will say yes. Tell them how much it will cost, and many start to hedge. Despite clear evidence (and common sense) that energy efficiency is a great long-term investment, additional construction cost often dampens the initial enthusiasm. Promoters of energy efficiency routinely find themselves justifying the extra cost as "worth it."

An effort--called Building America--is now underway to remove any need for justification. The goal of this applied research program is to find ways to cut energy use by 50 percent compared to current practice without increasing overall construction cost. That's right, zero increase in overall cost.

One key partner in Building America is Building Science Corporation (BSC) and its principals, Joe Lstiburek and Betsy Pettit. With their advice and encouragement, three production builders have demonstrated various methods of reaching the goal. Known as the Building Science Consortium, this group has already built 35 homes.

"The Building Science Consortium, as well as three other teams, have agreed to do specific research and test preselected systems related to building performance," says Pettit. By December of 1998, the total number of completed homes should reach 300. (See the sidebar for a list of participants.)

Systematic Thinking

BSC's strategy is to approach the house as an integrated system, not a collection of components. While the "house as a system" idea is not new, BSC has convinced large production builders to give it a try.

"If you spend money to improve the building envelope," says Lstiburek, "then you can downsize the heating and cooling system." Based on the projects so far, Lstiburek has found several cost- cutting ideas. Reduce the size of a heat pump and save between $300 and $650 per ton. Use water heaters for space heating, which cuts equipment cost and saves valuable interior space. Whenever possible, locate the air handler inside the conditioned space.

Lstiburek identifies additional savings by redesigning duct systems. Locate air supply registers near interior walls, instead of running ducts to the building's perimeter. Use flex duct to reduce material and labor costs.

Many designs used 12 to 14 in. open web floor trusses which allowed space for a single 10-in. diameter round trunk duct. Branch lines connected to the trunk with 45° take-offs to reduce resistance to air flow.

"These changes to the mechanical system can cut costs by $250 to $350," says Lstiburek. "But, it's critical that each system be carefully designed on a case-by-case basis."

Envelope Efficiency

Savings in HVAC equipment are made possible by dramatic reductions in heat loss and gain through the building envelope. All designs get an air sealing package that cuts air leakage by 30 to 50 percent. Air sealing and moisture control strategies are tailored to the climate. Instead of using housewrap, an exterior air barrier is formed by carefully caulking and taping exterior insulated sheathing. On the inside, drywall is glued to studs, and on the exterior, the sheathing is glued to studs, too. Careful attention to the boundary between inside and outside helps builders catch air leakage locations that escape the attention of many production builders. These include cantilevered floors, interior soffits and side attics in story-and-a-half designs.

Advanced framing is one way to cut heat flow and cost at the same time. Two-stud corners, 24-in. stud spacing and even single top plates help reduce the amount of framing to around 10 percent of the overall wall area, compared to as much as 30 percent for typical construction. Less wood and more insulation increases the building's overall R-value, while cutting material and labor costs.

Crew Training

Energy-efficient designs can be defeated by crews that don't understand or don't care. Recognizing this, BSC holds early morning training sessions on the job site. These sessions allow Lstiburek, who is widely known for his engaging presentations, to explain the concepts, show the techniques and build support for the new methods. BSC developed posters with detailed drawings to illustrate important techniques. These posters--sized to span 24-in. framing--are mounted on site as reminders.

Knowledge Base

"Sixty of the BSC homes will be monitored for energy use," says Pettit. "When the project is completed, we'll have a database of information on construction cost and energy performance." This information will help designers and builders make good decisions about energy-saving features. Soon, energy advocates may not need to justify the cost of energy-efficient construction.

Building America is sponsored by the U.S. Department of Energy with field support provided by the National Renewable Energy Laboratory. Four teams have formed to investigate and demonstrate housing innovations that improve energy efficiency and environmental responsibility while reducing construction cost. A team, called a consortium, comprises one or more building contractors, material suppliers and designers. Although USDOE provides some funding, most of the financial support comes from consortium partners in the form of matching funds.

The Building Science Consortium comprises Building Science Corporation, Shaw Homes in Chicago, Pulte Home Corporation in North Carolina, Michigan, Arizona and Nevada, as well as Town and Country Homes in Chicago and Florida. Other Building America teams include the Consortium for Advanced Residential Buildings, The Integrated Building and Construction Solutions Consortium, and the Hickory Consortium.

Lstiburek is author of several books, including the EEBA Builders Field Guides.