This site in Tucson's Barrio Libre Historic District was long vacant because of its challenging shape, topography, and zoning. We tucked the foundation into the slope, and built to height and setback limits. The 'Net Zero' design is a collaboration with Tucson Artisan Builders; it includes photovoltaics and real-time energy monitoring. Details include enameled steel shadow boxes around windows and 'lily pads' of colored concrete in the front garden.