This paper is based on findings resulting from ASHRAE Research Project RP-1254.

This paper provides an overview of the results of ASHRAE Research Project RP-1254, Evaluating the Ability of Unitary Equipment to Maintain Adequate Space Humidity Levels; Phase II: Simulations, Summary and Development of Guidelines. Whole-building energy simulations were used to perform a parametric analysis of eighteen HVAC system types in seven commercial building types (small office, large retail, 9 month classroom,12 month classroom, restaurant dining area, small hotel/motel guest room, and theater) using two sets of ventilation rates (ASHRAE Standards 62-2001 and 62.1-2004) in 10 locations. The system types included single-path and dual-path direct expansion (DX) with and without enhancements such as enthalpy wheel, demand controlled ventilation, desiccant dehumidifier, subcool reheat, hot gas reheat, and air-toair heat exchangers around the cooling coil. The relative performance of each system type is compared on the basis of humidity control (occupied hours >65% RH) and annual energy use, including heating energy. The systems are also compared for life cycle costs using approximate installed equipment costs and HVAC annual energy costs.

Units: Dual