Acceptable air velocities using demand-controlled ventilation for individual cooling

Abstract

One of the main challenges in highly insulated buildings is the increasing share of energy demand for cooling. New solutions for low energy cooling are needed. Individual cooling by demand-controlled ventilation and use of ceiling mounted nozzles for cooling by higher air velocities could be an alternative. A laboratory study was designed to investigate thermal comfort and thermal sensation for elevated indoor room temperatures relevant to Norwegian summer climate; 24℃, 26℃ and 28℃ with a relative humidity set point of 40 %. Air flow was set to give air velocities of 0.25 m/s, 0.50 m/s and 0.75 m/s. 21 test persons were exposed to different air velocities in a cross-over study. Questionnaires on thermal comfort and thermal sensation were answered repeatedly. Jets from ceiling mounted supply air nozzles was shown to improve thermal comfort at 24 °C, 26 °C and 28 °C. In general, most test persons preferred low air velocity (0.25 m/s) at 24 °C, while high (0.5 m/s) or extra high (0.75 m/s) air velocities were preferred at 26 °C. At 28 °C, extra high or even higher air velocities were preferred.