With basic passive solar and energy conservation measures in place, Williams specified a 3.3-kWh photovoltaic array and a solar hot water system, which together provide for 80% of the house’s electricity needs. The 16 panels are mounted on the metal roof of a detached carport/greenhouse/workshop that faces due south. Linked to the house by a covered walkway, the 1,272-square-foot building has the added benefit of housing the mechanical equipment and offering ample space for more PVs down the road.

Most of the home’s materials came from Texas. The project earned four LEED points for its use of plentiful local wood species, including Eastern red cedar porch columns, ceiling beams and trim, interior stair handrails, and master-closet shelving; reclaimed long-leaf yellow pine second-story flooring; and mesquite bathroom cabinets, entry floor, and stairs. Balcony handrails and balusters were cut from juniper found on the property, and some of the stone used on the building base, walkways, and fence was excavated on site.

Four additional LEED points came from a rainwater harvesting system that captures runoff from 100% of the buildings’ roof surfaces—enough to supply all the water needed for drinking and household use. Rainwater is stored in two 10,000-gallon above-ground tanks, which sit about 50 feet west of the house, and is pumped through purifiers and into the house’s supply line. Wastewater is run through an on-site sewage treatment system and sprayed back onto the landscape.

For the couple, avid gardeners, living off the land also meant growing much of their own food. They installed a drip irrigation system for the vegetable garden, but the drought-tolerant ornamental landscape needs scant water. Conservation continues inside the house with Toto’s 1.1-gpf toilets and 2.2-gpm faucets.

Although green certification was never an explicit goal, Williams’ trademark environmental rigor paid off. Tonalacalli earned the Austin Energy Green Building’s 5-Star rating—the program’s highest—and the distinction of being the first LEED-Platinum home in the city.