Analysis of the impacts of light shelves on the useful daylight illuminance in office buildings in Toronto

Modern envelope technologies and architectural trends often encourage the construction of buildings with large glazing surfaces. Glazed facades are often proposed with the intent to guarantee high daylight levels and wide exterior views. However, an increasing attention is nowadays recognized to glare issues and indoor comfort levels. Consequently, light shelves are often proposed to help reducing glare issues, providing better illumination distribution, and increasing the homogeneity of daylight distribution into the spaces. In this paper, the impact of light shelves over the illuminance levels in a south facing office building in Toronto is evaluated. The Useful Daylight Illuminance (UDI) is considered as the metric of analysis. Annual simulations for four different window-to-wall ratios (WWR) are compared with and without light shelves. Results show that light shelves enhance the UDI levels mainly in the first six meters in front of the windows, and provide a more homogeneous daylight distribution with an increase of the UDI for any considered WWR. Finally, this paper shows that WWR above 35% result in increasing daylight quantity with higher glare issues, and in case of the adoption of floor to ceiling windows, WWR above 35% are not advantageous in terms of daylighting.