Performance of internal venetian blind configurations for daylighting office spaces in context of Dhaka

Abstract

Most of the offices in Dhaka are located in high-rise buildings with deep plan layout due to constraint of space in urban areas. Contemporary glazed envelope technology in commercial buildings help to create a visual contact with the outside and lets daylight to enter especially in deep plan offices. In most cases high-rise commercial buildings do not use efficient shading elements. As a result, excessive daylight enters inside the office space causing glare, irregular daylight distribution, solar heat gain and visual and thermal discomfort. Shading elements reduce glare issues, provide improved illumination distribution, and ideally can also increase the daylighting penetration into the active work spaces. Internal venetian blinds are common type of shading system which consist of separate louvers and arranged equidistant from each other. It reflects light efficiently and ensures homogeneity of daylight illuminance by adjusting the louver angles while allowing view to the outdoors.

The aim of this research is to identify the characteristics of internal blinds to enhance the interior luminous environment of office spaces in the context of Dhaka. In order to study the performance of internal blind configurations, an active portion of workspace area of the case office floor is selected for simulation study, which has glass exterior walls on three of its sides. Different parameters of the venetian blind is studied, e.g. the slat geometry, configuration of slats and the distance between slats for each orientation. For this analysis, Useful Daylight Illuminance (UDI) is considered as the performance metric. Climate based dynamic daylight annual simulation is done using DAYSIM simulation program. The data from the simulation procedure is critically analyzed and compared with the base case when there is no blind provided.

The results suggested that for south, east and west orientations, internal venetian blinds with “inverted V” louver geometry at 45oangle is the most feasible for enabling optimal indoor illuminance. In terms of distance between slats, 160mm is suitable for south façade whereas for east and west directions, 70mm provides the best performance among the studied options. This research proposes feasible configurations for internal venetian blind that are suitable for high-rise buildings with glazed façades in three orientations (south, east and west) to ensure sustainable building design.