Low energy or high-performance buildings form a vital component in the sustainable future of building design and construction. Rigorous integrated daylighting design and simulation will be critical to their success as energy efficiency becomes a requirement, because electric lighting usually represents a large fraction of the energy consumed. We present the process and tools used to design the lighting systems in the newest building at the National Renewable Energy Laboratory (NREL), the Research Support Facility (RSF). Daylighting had to be integrated with the electric lighting, as low energy use (50% below ASHRAE 90.1-2004) and the LEED daylight credit were contractually required, with a reach goal of being a net-zero energy building (NZEB). The oft-ignored disconnect between lighting simulation and whole-building energy use simulation had to be addressed, as ultimately all simulation efforts had to translate to energy use intensity predictions, design responses, and preconstruction substantiation of the design. We present preliminary data from the postoccupancy monitoring efforts with an eye toward the current efficacy of energy and lighting simulation methodologies.