Daylight prediction based on the VSC - DF relation
Abstract: In 2017, 255 of Sweden's 290 municipalities reported a shortage of residential housing (Boverket, 2017). The answer is to build more. Due to urbanization pressure, concerns for saving valuable agricultural land, growing national and EU demands on energy-efficiency, there is an increasing number of new and dense urban developments. Daylight issues seem to have been of little concern in development of many of these new detailed plans, and daylight in buildings is often studied much too late into the project. The aim of this master thesis was to seek through computer simulations for a simple method to assess daylight availability in residential housing at an early design phase. It is based on a presumed relationship between the median Daylight Factor and the in Sweden rather unfamiliar Vertical Sky Component (VSC). Both the VSC and median Daylight Factor where evaluated for a simple room geometry located on the ground floor of five courtyard building typologies. Our aim was to obtain general threshold values of VSC to ensure that the Swedish national requirements of good access to direct daylight can be met. Additionally, the impact of both Glazing-to-Floor Ratio and the room depth on the base-case O-shaped typology was assessed and a guideline was formed. A target VSC was found to be 29% to assure DFmed 1% indoors with conventional window and room design. Following the guideline, in the façade areas where VSC is below 15% it would be difficult to reach the target DFmed. The performance of the proposed method was evaluated against common threshold values and rules-of-thumb. It was found that predictions from the established principles were often too optimistic.
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