The benefits of light shelves over the daylight illuminance in office buildings in Toronto

Modern envelope technologies and architectural trends often encourage the adoption of large glazing surfaces. Light shelves are then proposed to reduce glare complaints, while providing better indoor daylight distribution. In this paper, the benefits of light shelves over the illuminance levels in office buildings in Toronto are evaluated. The useful daylight illuminance was used as the metric of analysis in this study. Annual simulations for buildings with different window-to-wall ratios were compared. Moreover, the effects of different window shapes, façade orientation and external obstructing elements were investigated. Results show that in the context of analysis, light shelves increase the useful daylight illuminance values mainly in the first 6 m from the windows and provide a more homogeneous distribution of the daylight. Window-to-wall ratios above 35% consistently result in increasing glare risks. This study indicates that narrow full-height windows provide better daylighting compared to shorter but wider windows. The west orientation shows higher useful daylight illuminance compared to the south-facing ones, although light shelves are far less beneficial when applied to windows but not facing south. Finally, the illuminance levels in buildings with different obstruction angles of the façade are presented in order to provide a comprehensive analysis about the benefits of adopting light shelves in office buildings in the urban context of Toronto, Canada.