The absolute energy consumption target was chosen based on analysis done as part of a sector-wide energy efficiency modeling study (Griffith et al. 2006). As part of that study, energy models of all the buildings in the 2003 Commercial Building Energy Consumption Survey were created using EnergyPlus. These models were then modified to make them minimally compliant with ANSI/ASHRAE/IESNA Standard 90.1-2004 requirements. Tables containing these results are available online for the industry at large to facilitate energy goal setting. An absolute energy use intensity goal was chosen to correspond to half the average energy use of the simulated office/professional buildings in ASHRAE climate zone 5B, which includes Golden, Colorado. This goal was in line with the measured performance of several high-performance office buildings analyzed in detail by the Commercial Buildings group at NREL (Torcellini et al. 2006). Further feasibility studies carried out in 2007 indicated that this target should be achievable for an office building in the Denver area if special attention were paid to optimizing glazing area to maximize daylighting yet minimize thermal losses; emphasizing the building's east- west axis to facilitate the daylighting goal (daylight is easiest to control and harness from the north and south); and minimizing plug and process loads. The modeling study used NREL-developed design optimization software to explore design options that could lower end-use energy consumption. The optimization modeling begins with an initial baseline whole-building energy model then systematically alters the design features, at each stage selecting the most cost-effective energy saving design options.