Arthur Andersson, AIA, looked to Southwestern cliff dwellings when designing Block 21 in Austin, Texas. The mixed-use project contains the television studios and performance venue for “Austin City Limits,” office and retail space topped by a W hotel, and private residences. Those high-rise caves inspired him to design shaded balconies carved into the east and west façades, for longer hours of daylight without heat gain. Shading is key, because staving off the Texas heat consumes large amounts of energy. The project's high-performance glazing blocks UV rays and reflects heat away from interiors while providing natural light. But the building still needs cooling, so Andersson found an alternative method in Austin's central water-chiller system. “You buy cold water from the city's central chiller and when it gets hot, you send it back,” he explains. “But we're designing an intermediate step where we send the water through a heat-recovery system.” That step garners heat for the building and saves energy for the central chiller.
Another innovative idea helped shrink the parking structure. The 37-story building requires mostly nighttime and weekend parking, while nearby commercial buildings use garages during business hours. A shared parking agreement lets Andersson get away with just 450 spots—about half the usual requirement. Block 21 currently qualifies for LEED Platinum status, and the team feels strongly they'll be able to maintain that status throughout construction, which concludes in 2010.
project: Block 21, Austin, Texas key green strategies: Green roof, xeriscaping, low-flow fixtures, low-VOC paints and adhesives, local materials, optimal daylighting, on-site recycling, high-performance glazing, central water-chiller system, and mixed-use
architect: Andersson–Wise Architects, Austin
architect of record: BOKA Powell, Dallas
developer: Stratus Properties, Austin
general contractor: Austin Commercial, Austin
project size: 638 square feet to 4,204 square feet per unit
site size: 1.76 acres
construction cost: $275 per square foot
sales price: $300,000 to $1.5 million per unit
units in project: 196 (plus 250 hotel rooms)