Impact of Reduced Air Temperature and Increased Radiant Temperature on Perceived Air Quality, Thermal Comfort, SBS Symptoms and Performance

The present Thesis investigates the impact of reduced air temperature on perceived air quality, thermal comfort, SBS symptoms and performance. The impact was investigated in an experiment that exposed 28 thermally neutral subjects to three 3-hour exposures of typical office environments. The reference condition exposed subjects to air at 23°C. The two additional experimental conditions exposed subjects to air at 18°C; one condition with a pollution source present in the room. The ventilation rate was high at all conditions (6 h-1, corresponding to 45 l/s/person). The exposures were carried out in a real office, in which temperature, humidity and ventilation rate could be controlled. The office had four workstations where the subjects solved general office tasks with which their performance was measured. At regular intervals the subjects filled in questionnaires regarding the perceived air quality, thermal comfort, their immediate health condition and their perceptions regarding the indoor environment. Thermal neutrality of the body was obtained by using radiant heating and by allowing the subjects to adjust their clothing. Radiant heating was used in conjunction with adjustment of clothing as a means to reduce thermal discomfort caused by clothing insulation asymmetry. Electric foils supplied the radiant heating. A set of four radiant heating panels was designed and built for each workstation as part of the Thesis. Reducing the air temperature from 23°C to 18°C significantly decreased the number of dissatisfied with the air quality from 20% dissatisfied to 6% dissatisfied. The air at 18°C was also perceived as being fresher than the air at 23°C. Though thermally neutral under all conditions, the thermal acceptability of the body was lower at 18°C than at 23°C, due to higher local thermal discomfort. This was caused by increased draught and clothing asymmetry at the 18°C condition. A tendency towards preferring a thermal sensation of the body higher than zero was observed at both temperature levels. A tendency towards a lower prevalence of symptoms among subjects exposed to air at 18°C was found. The tendency was not statistically significant, but assessments of different symptoms consistently showed the same tendency. No impact on performance of changes in neither air temperature nor pollution source was found. Reducing the air temperature thus increased the acceptability of the air quality, while decreasing the thermal acceptability. This could have had an impact on the small difference in symptom prevalence. No significant change was found in the subjects’ assessments of the general indoor environment between the two temperature conditions. Reducing the air temperature and adding a pollution source decreased the percentage dissatisfied with the air quality from 20% to 14%. The polluted air at 18°C was more satisfactory than the unpolluted air at 23°C, but less satisfactory than the unpolluted air at 18°C. Females were more dissatisfied with the polluted air than males. Reducing the air temperature and introducing a pollution source significantly increased the percentage dissatisfied with the general indoor environment. A tendency towards the prevalence of symptoms being highest when exposed to the polluted air was found.