In line with the mission of the National Park Service, the Zion National Park Visitor Center was designed to use 70% less energy than a comparable visitor center built to Federal Energy Code 10 CFR 435 (DOE 1995). The authors and NPS staff used an integrated design process, including extensive simulations, to minimize the energy consumption. The result was a passive solar commercial building that has a good thermal envelope, daylighting, and natural ventilation. Passive downdraft cooltowers provide all the cooling. Two Trombe walls provide a significant amount of the heating. After two years of metering, the results show a net energy use intensity of 24.7 kBtu/ft² (280.5 MJ/m^{2) and a 67% energy cost saving. Low energy use and aggressive demand management result in an energy cost intensity of $0.43/ft2 ($4.63/m2). The paper discusses lessons learned related to the design process, daylighting, PV system, and HVAC system.}

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