All builders in Whisper Valley are required to hook up to EcoSmart’s GeoGrid, a 5-mile loop of underground distribution piping that links each home to a geo-exchange network, engineered and manufactured by REHAU, a global provider of hydronic technologies and a strategic partner in the Whisper Valley project. “It took a bit of time to figure out who was doing what,” says Dennis Ciani, head of marketing for Pacesetter Homes, an Austin-area builder that constructs about 500 homes per year, including most of the new homes in Whisper Valley. “But the geothermal loop was already in the ground and all homeowners had to do was tie into it, which turned out to be fairly easy