Many studies have shown that floor-supply displacement ventilation systems are better than mixing ventilation systems. The benefits include indoor air quality, thermal comfort and reduced energy use. The energy benefits depend on the climate conditions. This research compared the energy use of a, floor-supply displacement ventilation system in a large industrial workshop with that of a mixing ventilation system for five U.S. climate regions. It was found that the energy use and the system performance vary with the locations. The displacement ventilation system may use more fan and boiler energy but less chiller energy than the mixing ventilation system. The total energy used is slightly less with displacement ventilation, although the ventilation rate was increased in order to handle the high cooling loads found in U.S. buildings. Thus, the displacement ventilation system can save some energy in cooling mode. However, displacement ventilation system has a lower capacity of dehumidification. This system alone, thus, is not suggested for use in humid regions. (C) 2006 Elsevier B.V. All rights reserved.