When the Bakers—father James and sons Scott and Brian—launched studio26 homes five years ago, green was still just a buzzword in Eastern Pennsylvania’s Lehigh Valley. But the trio saw the deepening shift in consumer awareness and decided to make super-energy-efficient houses their calling card. For starters, their goal was to reduce energy use by at least 40% compared to other homes built to code.
The Bakers tapped the brain trust at Building America, a research program sponsored by the U.S. Department of Energy. And to make sure their best practices keep hitting the benchmarks, every studio26 project is analyzed by Integrated Building and Construction Solutions (IBACOS), a Building America partner consortium that offers energy modeling. “They do takeoffs of our plans and specs and also work through a general HVAC design,” says Brian, studio26 homes’ vice president of marketing and design.
The latest result of that collaboration is a house in Orefield that earned a Gold rating under NAHB’s Model Green Home Building Guidelines. Its 542 points, earned primarily through indoor air quality and an airtight building envelope that minimizes thermal bridging, far exceeded the Gold minimum of 395 points.
In this case, the design team began with a significant asset on its side: The 1.2-acre parcel’s gentle, south-facing down slope provided the ideal conditions for passive solar heating and daylighting. To ensure sufficient sun exposure throughout the day, not only for passive solar gain but for a future PV installation, the Bakers rotated the house to within 20 degrees of due south. With the long axis running east-west and the rear facing south, all three levels are open to solar gain and are filled with natural light. The contemporary Craftsman style also plays into passive cooling with deep overhangs, porches, and a long Trex deck across the back that shades the walk-out basement.
Given Pennsylvania’s cold winters, super-insulating the walls was a top priority. The builders installed an Xi concrete-and-Styrofoam foundation system from Superior Walls made of 10¼-inch-thick, 10-foot-high sections pre-insulated to R-12.5.
And to increase the energy performance of the foundation walls, the crew installed R-21 formaldehyde-free Johns Manville fiberglass batts into the stud cavities, which raised the basement walls’ overall R-value to 33.5.
The builders tightened the 2x6 wood-framed envelope by adding 1-inch extruded polystyrene to the exterior. All the wood-framed walls were tightly insulated with blown-in, R-23 Johns Manville Spider Custom Insulation, installed at 1.8 pounds per square foot to fill gaps. Using these measures, studio26 was able to beat Building America targets for air leakage. A blower-door test showed 0.101 NACH (natural air exchanges per house), compared to the benchmark 0.131 NACH. A duct-blaster test resulted in 0.5% air leakage, an improvement over Building America’s 1% target.