scope:

PURPOSE OF THIS GUIDE

Underfloor air distribution (UFAD) systems are innovative methods for delivering space conditioning in offices and other commercial buildings. Underfloor air distribution derives its name from the use of the underfloor plenum below a raised (access) floor system to supply conditioned air directly into the occupied zone of the building, typically through floor diffusers. The use of UFAD technology is increasing in North America because of the benefits that it offers over conventional overhead air distribution.

The purpose of this design guide is to provide assistance in the design of UFAD systems that are energy efficient, intelligently operated, and effective in their performance. This guide also describes important research results that support current thinking on UFAD design and includes an extensive annotated bibliography for those seeking additional detailed information. This guide does not cover conventional overhead air distribution system design procedures in depth but rather focuses on the major differences between UFAD systems and conventional design. For more information on standard heating, ventilating, and air-conditioning (HVAC) design, please refer to other books published by ASHRAE, including the Handbook series [ASHRAE 2000, 2001a, 2002, 2003a], Air-Conditioning Systems Design Manual [ASHRAE 1993], and Designer's Guide to Ceiling- Based Air Diffusion [Rock and Zhu 2001].

Task/ambient conditioning (TAC) systems are a special class of air distribution systems characterized by their ability to allow individuals to have personal control over their local environment, without adversely affecting that of occupants in the surrounding area. A large majority of TAC systems use UFAD with furniture- or partition-basedsupply outlets because of the effectiveness of this configuration at providing individual control for nearby occupants. These two closely related air distribution systems share many common features in terms of their design, construction, and operation. This guide also presents preliminary design guidance for TAC systems where available, although applications and experience using this technology are still rather limited.

The development of this guide is based on a compilation of available information, including research results from laboratory and field experiments and simulation studies, design experience described in the literature as well as from interviews with practicing engineers, manufacturer's literature, and other relevant guidelines from users of the technology. Despite recent growth in the UFAD market, widespread experience with these systems is still at an early stage, with significant issues the subject of ongoing research. The guidelines presented here are based on the most current and best available data and information. Designers and operators are encouraged to use common sense and good engineering judgment when applying methodologies described in this guide. The guide is intended for use by design engineers, architects, building owners, facility managers, equipment manufacturers and installers, utility engineers, researchers, and other users of UFAD technology.