Sensation of draft at ankles for displacement ventilation and underfloor air distribution systems
Draft is defined as an unwanted local convective cooling of the body caused by air movement (Fanger, 1977). The main factors that affect draft are air temperature and velocity (Houghten et al., 1938), air turbulence (Fanger et al., 1988), body parts exposed and clothing insulation level, and overall thermal comfort (Toftum et al., 2003). Historically, the literature on draft has focused on thermal discomfort at the neck, which was considered the most sensitive part of the body, especially as the majority of mechanical systems supplied air from the ceiling. Now, owing to the widespread use of floor-level air distribution systems (underfloor air or displacement) and dress customs in which ankles could be uncovered, the need to assess draft risk for the ankle has emerged (Sekhar and Ching, 2002). The purpose of the present study is to experimentally evaluate local draft risk for uncovered ankles associated with displacement ventilation and underfloor air distribution.