Cognitive performance evaluation under controlled daylight levels at different indoor temperatures

This paper details the results of an experimental study investigating the influence of daylight illuminance levels and indoor temperatures on objective and subjective performance evaluations, investigated through paper-based tasks and questionnaires, respectively. Experiments were conducted in an office-like test room with controllable indoor temperature and easy-to-change glazing visible transmittance. A total of 84 participants took part in the experiment, performed only under clear sky conditions to avoid variations in illuminance. In a randomized order, participants were exposed to three daylight illuminance levels (on average 140, 610 and 1440 lux) at one of three temperature conditions: 19, 23 and 27°C. Results show that objective performance outcomes were not affected by daylight illuminance or temperature, nor by their interactions, but only by the order of the test presentation ( indicating a learning effect). Of the subjective responses, only perceived concentration was affected by daylight conditions, with a self-reported lower concentration under the low illuminance level.