Production Home Sets New Standard

Paul Davis of Steven Winter Associates measures the thermal performance of a window in the Carborne home using mean radiant temperature globes.

The Carborne design was developed with the occupants in mind. A focus group was brought together to suggest improvements.

Ryan Homes of New York recently built a prototype single-family home that sets a new standard for affordable, energy- and resource-efficient buildings-and has the data to prove it. Located in a suburb of Rochester, New York, the Carborne is a three-bedroom, one-and-a-half-bath home of just over 1,200 ft2. It is intended to sell for about $95,000. The home uses 30% less heating energy than a home that just complies with the International Energy Conservation Code (formerly the Model Energy Code-see page 7), and it exceeds the demands of the Energy Star Homes program.

Project manager Don Clem is a senior architect with Steven Winter Associates (SWA), the firm that designed the Carborne in collaboration with Ryan Homes. Ryan's standard house and construction methods are already meeting advanced energy codes, Clem says. It was a challenge to make improvements.

Though similar in appearance to its residential neighbors, the Carborne prototype incorporates several unique components. The design features integrated steel and engineered wood framing; high-efficiency heating and ventilation; and Owens Corning Systems building products, including shingles, siding, ridge vents, ice dam barrier underlayment, and insulation. The improved performance of the Carborne's building envelope enabled designers to use a smaller, more efficient heating system. The home has R-15 insulation in the walls and R-38 in the ceilings. The windows are double-glazed, low-e, and argon filled. The typical wintertime natural infiltration rate is reduced by 30%, from .32 ACH to .22 ACH.

According to SWA building scientist Pawan Kumar, As a result of tighter construction, better insulation in the walls, and high performance, low-e windows, we were able to pull the supply air registers away from the exterior walls. The shorter duct runs saved on first costs and resulted in substantial energy savings, without any adverse effects on occupant comfort. All the ducts were installed in conditioned space, further reducing energy losses.

The prototype Carborne was equipped with mean radiant temperature sensors and infrared cameras, and for two weeks SWA and National Renewable Energy Labs (NREL) staff collected data, took tracer gas measurements, and performed blower door, coheating, and duct leakage testing. This monitoring and testing was designed to gauge heating energy use, envelope thermal performance, whole-house infiltration, and heating system efficiency.

A control, or base case, house located adjacent to the prototype was outfitted with the same set of sensors. The base case house is a standard Ryan Homes design, and incorporates more traditional building materials and methods using panelized wall and roof trusses. The proximity of the two homes, coupled with their similar floor plans and siting orientation, allowed highly accurate energy performance comparisons.

Tests showed that the mean radiant temperatures at the windows and in the center of a room vary by only 0.5°F in the Carborne, as opposed to 3°F in the base case house. This results in better comfort near the windows in the Carborne house, even though the heating registers are far from the exterior walls.

Along with these comfort features, the house has an overall design that aims to please potential residents. It has an open floor plan that makes the most of its architectural and structural elements. Though the house itself is relatively small, a half-wall separating the kitchen from the great room lends a feeling of spaciousness, a characteristic that is further enhanced by the preponderance of windows. When work on the Carborne commenced, Don Clem convened focus groups of potential home buyers in the Rochester area. The members of these groups were later invited to the finished house and were questioned on their impressions of the final product.

Across the board, they were enthusiastic about the Carborne and expressed their willingness to pay higher first costs in return for more energy-efficient windows, HVAC systems, and insulation. One person saw the Carborne's energy efficiency features as exerting a favorable influence on resale value. If you're looking to resell five years from now, new houses might have these features, she noted, adding that the Carborne's energy-efficient design and technologies are a good investment for the future ease of reselling.

Carl Smith, vice president of Ryan Homes New York, expects the Carborne to be made available soon as part of the company's standard residential lineup.

The home was developed with technical support from Steven Winter Associates Incorporated, under the auspices of the Consortium for Advanced Residential Buildings (CARB). The project is part of the U.S. Department of Energy's Building America program. Technical support was provided by the National Renewable Energy Laboratory (NREL).

-Will Zachmann

Will Zachmann is the director of communications for Steven Winter Associates Incorporated in Washington, D.C.

Publication of this article was supported by the U.S. Department of Energy's Office of Building Technology, State and Community Programs, Energy Efficiency and Renewable Energy.
 

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