Daylight: Virtual sky component

Intro

With this tool you can simulate the VSC (virtual sky component) for early concept volume studies. VSC can provide a good early predictor for indoor daylight performance.

VSC is computed at points on the buildings facades to measure how much each point is illuminated by light from the sky. This informs how much light would shine through windows placed at those points, thus providing an indication of how a facade can contribute to indoor daylight conditions.

Tips

VSC & Daylight Factor. Daylight Factor assesses illuminance inside the rooms of a building, whereas the VSC analysis assesses illuminance outside on the facades of the building. Where VSC only measures for direct light from the sky on the facades, Daylight Factor uses knowledge of window details and material reflective properties to measure direct and reflected light coming in through windows. However, direct light from the sky through a window is typically the main contributing factor to a DF score, and VSC can therefore provide a good early predictor for indoor daylight performance. DF and VCS use the same sky model: CIE standard overcast sky.

VSC thresholds (given a target of 2% average daylight factor):

VSC ≥ 27% Conventional window design usually satisfactory

15% < VSC < 27% Larger windows/changes in layout are usually needed

5% < VSC < 15% Difficult to provide adequate daylight

VSC < 5% Achieving reasonable daylight is often impossible