Leed, risks and rewards for builders

From: ECOHOME September-October 2011
Posted on: September 22, 2011

Risks & Rewards
A North carolina home reads like a playbook for optimized building science techniques with the certifications to prove it.

By:
Jennifer Goodman
Name: Bryant Residence, Saxapahaw, N.C.Size: 2,498 square feetConstruction cost: $158 per square footCompleted: June 2009Certifications: LEED-Gold, NGBS-Gold, Energy Star, Builders Challenge, Green Home Builders of the Triangle-GoldHERS rating: 48Designer/Builder: Chandler Design-Build, Mebane, N.C.Energy Consultant: Southern Energy Management
Risks & Rewards

Custom builder Michael Chandler, well-known in North Carolina and beyond for his high-performance homes and highly personalized customer service, loves to challenge himself in the field with new products and technologies. As a veteran green builder and building science enthusiast dedicated to staying on top of cutting-edge techniques, he looks forward to learning something new on every job, and owning his business gives him the leeway to try new approaches.

“You can do things that are really kind of adventurous, and your only risk is that you might have to go back and fix it if it doesn’t work out,” he says. “You get to take a lot of chances.”

For this home about 12 miles west of Chapel Hill, N.C., he had the luxury of clients who are as adventurous and open-minded as he is. Although they originally asked Chandler for autoclaved aerated concrete walls that would recreate the thick, stone exteriors of the their childhood homes in England, Chandler quickly talked the husband and wife into something more affordable, more insulating, and more appropriate for North Carolina’s hot and humid weather. He saved $60,000 by suggesting a technique he had never tried before: double-stud wall construction, which cost only $4,200 more than the company’s standard 2×6 walls. That approach allowed room for nearly 12 inches of R-46 Johns Manville Spider spray fiberglass insulation between the walls and R-30 Icynene open-cell spray foam at the roofline. “We got a really good R-value at a really good cost with the double wall construction,” Chandler says.

Framing was completed in less than two weeks because the walls, floor, and roof were manufactured off site at local panelization plant Builders First Source. At the factory, the exterior was sheathed with OSB and then moved to the site, where crews wrapped it with Tyvek Wrinkle Wrap, two layers of asphalt felt, and SpiderLath and then finished with fire-resistant stucco, which provided the Old World look the owners were after at a fraction of the cost.

The 13-inch-thick walls created the same effect on the interior, with deep window jambs and sills usually found in thick masonry construction. “It’s really striking, especially where we have triple windows,” Chandler says.

Three rooftop solar thermal collectors provide domestic hot water and first-floor in-floor heating. The system includes an outdoor reset mixing valve that adjusts the temperature of the water in the floors in response to the outdoor air temperature. For backup, Chandler speced a 94% efficient Quietside 120-ODW natural gas condensing on-demand water heater; a Morso wood stove also helps keep the chill away in winter.

Chandler and his energy consultant chose a cooling system that would work with the tight envelope to keep utility bills ultra-low, even during the area’s sweltering summers. With the help of energy modeling software, they speced a zoned bypass system with a single air handler and optimized dehumidification function. “When you get to a house that’s this energy efficient you can’t just go by the old rules of thumb to design air conditioning,” he says. He keeps a close eye on the home’s gas and electric bills, which have averaged about $58 a month.

Beth Williams, Chandler’s wife and business partner, designed the two-bedroom home with a downstairs office that doubles as a walker-accessible guest suite for visits from the owners’ parents, with private access to the hallway powder room. For year-round outdoor living, she added a second-story roof deck and garden that’s out of reach of the local deer population and where the owners, aviation buffs, can relax and enjoy the action at the neighboring airpark.

The yard features native plants and grasses instead of water-guzzling turf. Two rainwater catchment systems send stormwater to the yard’s planting beds and vegetable garden, where a simple but ingenious process based on septic systems and designed by Chandler takes over. A series of 18-inch-tall, 5-foot-long arches called infiltrator chambers are set in trenches under a layer of gravel in the dense clay soil. Rainwater rises from these storage chambers into the retaining wall planter and ornamental garden by capillary action without any pumps.

“The arches have slits that allow the water to passively escape into the soil and water the plants that way,” Chandler explains. “It’s a nice, natural way to water the plants.”