Daylight penetration in Malaysian high-rise office buildings

Abstract

In our natural environment, there is an abundance of daylight. Before the invention of electric lighting, it was a primary source of interior illuminance. However, in today’s office buildings, daylight is being underutilized and dependency on artificial lighting is very common. Daylight use can be an energy saving feature of a building by reducing demand for electric lighting. It is very difficult to provide adequate amount of daylight all through a side lit space. Therefore, the knowledge regarding depth of its penetration is important for its proper utilization. This requires detailed daylight analysis. Standard skies are a very important part of this analysis. Recently, sets of fifteen skies have been adopted by the CIE (Commission Internationale de L’eclairage) as standards for the entire globe. These have not yet been incorporated into daylight simulation software. In order to incorporate these standard skies, the study has analysed the depth of daylight and permanent supplementary artificial lighting for interiors (PSALI) in high-rise office under hot-humid climate of Peninsular Malaysia using an alternative method. The study used ‘Daylight Coefficient’ to perform daylight calculation. ‘Waldram Diagram’ has been used to calculate the visible sky needed for the daylight coefficient method. Two experiments were conducted to find the upper and lower limits of daylight penetration throughout the year. The lowest levels have been analysed to determine the limiting depth of daylight while the difference between the lowest and highest penetration was considered for PSALI. The research found the depth of daylight was 3 m and 3.5 m from an adjacent window considering the lower limit for daylight of 500 lux and 300 lux, respectively. It also found that the depth of PSALI is different for different orientations. It is greater in the North-East, East, South-East, South-West, West and North-West directions compared to North and South orientations. This is due to the low solar altitude in the morning and afternoon. The research therefore, concludes that these depths may be taken under consideration in the pre-design phase of an office building in order to take maximum advantage of daylight usage in an office interior environment.