A team of researchers from UC Berkeley, Nanyang Technological University in Singapore and Stanford University have published the results of a study which show that thermal comfort, perceived air quality and symptoms of sick building syndrome are reported to be equal or better at 26°C and at 29°C, rather than at the common “set point” of 23°C, if a personally controlled fan is used.
50% of electricity in Singapore is consumed by commercial and residential buildings, mainly to supply air conditioning and to dehumidify air conditioned spaces.
According to the study, the best cognitive performance, as indicated by task speed, was recorded at 26°C. The typical indoor air temperature set point of 23°C yielded the lowest cognitive performance.
At 29°C, the availability of an personally controlled fan partially mitigated the negative effect of the elevated temperature.
Five experiments were conducted in the summer of 2014, with 56 participants dressed in typical Singaporean office attire – long pants, a short-sleeved shirt, socks and closed-toe business shoes – and assembled in a room at Nanyang Technological University which had an open-office layout with no cubicles. Relative humidity was controlled at 60%, a typical indoor level in Singapore.
In two of the tests (26 and 29°C), subjects were allowed to control air movement with personal electric fans if they wished. The tests used energy-efficient desk fans that run on more efficient DC motors using between 3 and 17 watts, rather than AC motors that use around 100 watts.
The researchers concluded that, if applied to commercial buildings in Singapore, increasing the indoor temperature set point to values in the range of 26-29°C and simultaneously providing occupants with personally controllable fans could could save up to 35% of the energy for air conditioning.
They are now working on smart fans that can adapt automatically to the environmental conditions and provide the needed comfort.