Buildings in the US account for 39% of CO2 emissions, 40% of energy consumption and 13% of water consumption. They also occupy valuable land, contribute to urban heat islands, atmospheric pollution, and landfill waste. More and more building owners and municipalities want a standard to use as the basis for code requirements for buildings designed to exceed minimum building codes. ASHRAE Standard 189.1-2011 #Design of High-Performance Green Buildings# recognizes these facts # it#s a mandatory-language code-intended standard with provisions related to building sites, water use, energy efficiency, and general environmental impact, in addition to indoor environmental quality. This Trane Engineer#s Newsletter program presents an overview of the standard and its reference standards, andprovides some insight regarding its potential impact on building designs, building codes and rating systems.