Aviary hen housing system is one of the alternative egg production systems that are being used by some U.S. egg producers. The motivation for adopting such a housing system is to improve bird welfare by allowing the hens to exercise natural behaviors, such as foraging, dust-bathing, and perching. However, research-based information on the overall performance and thus sustainability of the system is meager under U.S. production conditions. The goal of this field study is to comprehensively evaluate the performance of the housing system under Midwest production conditions with regards to animal welfare, environmental impact (both indoor environment and air emissions to the atmosphere), bioenergetics (for design and operation of heating, cooling and ventilation system), energy use, production economic efficiency, and microbiological quality.