Occupant density and daylight illuminance level fluctuation for office building in Malaysia

Abstract

Daylighting has yet to be fully utilised in the office interiors even though Malaysia has abundant natural light throughout the year and highly dependent on artificial lighting. However, there is always fluctuation of illuminance in office spaces and this can cause problems to occupants which affect visual and work performance. The aim of this study is to investigate fluctuation in daylight illuminance that affects visual comfort and visual performance. This study also investigates the effects of occupant density in office space in a typical layout of office building. In the first phase of the study, a visual test has been conducted involving seventy two office workers and assessment using a questionnaires survey on one hundred and eighty one office workers. Experiment through visual test was conducted in the office space which involved groups of occupants in office buildings. Furthermore, four groups of office workers numbering five, ten, fifteen and twenty per group were subsequently assigned to the office to detect fluctuations by computer simulation using IES Software. The result of the experiment evidenced that the level of illuminance in the office was 300 lux to 400 lux while preferred illuminance level was 280 lux to 350 lux. However, the occupants performed their tasks well in higher illumination range of 400 lux to 600 lux. Findings from experiment of visual performance and daylighting simulation showed there was fluctuation influenced by the number of occupants. When occupancy was less than 50%, the fluctuation was acceptable for visual comfort. However, when the occupancy was more than 50%, it would lead to higher fluctuation and the illumination level of recommended standard (300 lux to 400 lux) was not achievable. The findings contribute towards the improvement of an acceptable visual comfort ranges for Malaysian Standard of lighting condition and assist architects and designers to have better understanding in quality and quantity of daylighting and strategies on energy saving.