The two building science experts who led the project stressed health, durability, comfort and efficiency
Chris Little of eleV8 Design and Builders and Andrew Wagner of BASF poured their considerable building-science expertise into this luxury spec house in the Spanish Oaks neighborhood in Austin, Texas.
PROJECT PROFILE
Zip Code » 78738
Neighborhood » Spanish Oaks
Building Area » 5070 sq.ft.
Rating Date » 2013
Architect » Andrew Wagner, AIA
General Contractor » eleV8 Builders (Chris Little, president; Monika Little, chief financial officer; Jason Selgert, project manager; Arwen Shackelford, office manager)
A pilot project for the fledgling firm, the 5,100-square-foot home demonstrates that sustainable construction is compatible with comfort and beauty. Little is a builder who studied the physics of heat and moisture flow in buildings and worked in building forensics. He met Wagner, a performance-minded residential architect, at BASF.
After launching eleV8, Little says, “we had to show what our capabilities are. I’ve been out preaching high performance gospel for the past decade, and now it was time to practice it.”
ENVIRONMENTAL FEATURES
How do you get wealthy homeowners unconcerned by monthly utility bills to care about green building? Little’s solution: focus on performance. “I’ve always been a champion of green-building, but ‘high performance’ is the term we like to use,” Little says. “High performance captures the four pillars we want to deliver: health, durability, comfort and efficiency. It’s the result of doing everything right.”
Advanced Framing
The home features a 24-inch-on-center base for studs, joists and rafters rather than the standard 16-inch-on-center base. Advanced framing—especially in a complex custom layout—requires more planning and craftsmanship but works because everything in the vertical load path lines up—roof trusses with second floor studs with floor joists with first-floor studs. The result is up to 25 percent less wood in the walls, less wood waste during construction and more room in the walls for insulation. “The trick is to plan from the roof down how to carry the load, versus from foundation up,” Little says.
Insulation Innovation
This is the first home in North America to feature SPRAYTITE® closed-cell spray foam insulation by BASF, with OpteonTM 1100 (previously known as FormacelTM 1100) expansion agent from Chemours. Together they nearly double insulation performance while reducing greenhouse gas emissions. Closed-cell spray foam insulation at a thickness beyond 2 inches becomes a vapor retarder. eleV8 used a flash-and-fill system—flashing the walls with an inch-and-a-half of closed cell and filling the remainder with blow-in bats. Combined with Zip Wall’s R-3 rigid exterior sheathing, they achieved an R-value of 26 throughout the house.
“This house was designed with extensive advanced framing techniques, using less lumber and yet is more structurally sound. The framing leaves more room for insulation, so the house has better thermal performance. Good design helps you build green at no additional cost.”
— Miki Cook, Green Building and Sustainability Consultant Senior, Austin Energy Green Building
Passive Ventilation
At the home’s core, an attractive tower with motorized windows acts as a solar chimney to draw cool air through operable windows around the home’s perimeter during the shoulder seasons on either side of summer.
Optimized Systems
The home’s orientation and glazing takes advantage of natural lighting, with 95 percent of the artificial lighting provided by LED or compact fluorescent bulbs. A variety of water-conservation strategies were used, including on-demand hot water with integrated recirculating hot-water loops. The 22 SEER HVAC system was precisely chosen to fit the living space. The team prewired the home for solar panels and left more than 1,000 square feet of unobstructed roof space to house them. With a PV system, the designers predict the home could easily operate at net-zero energy usage.
