Abstract

Commercial and institutional buildings are being designed with increased transparent areas of the façade. Provision of views to the exterior is desirable, but more importantly, human health and productivity benefits may result from well day-lit interior spaces. The increased use of natural light, coupled with daylight responsive lighting systems, can reduce the peak electrical load and internal heat gains caused by artificial lighting. However, excessive transmission of solar irradiance can result in a net increase in energy consumption required for cooling, and may also affect the visual comfort of occupants. Manually operated shading devices are commonly used to deal with this problem, though their control is generally not optimal. This thesis investigates the potential of an automated model-based control strategy for diffuse reflecting venetian blinds. Radiosity theory was used to numerically approximate the transmittance of a blind and glazing system for clear-sky conditions, and to determine the venetian slat angle required to maintain favourable transmission values based on the HVAC demand and the visual comfort of the building occupants. Experimental measurements were carried out using a controlled motorized venetian blind installed on a clear glass window unit in a small-office space. The daylight transmission of the system was quantified and compared to the modelled prediction. A dimmable luminaire was also installed in this zone to determine the electric lighting energy savings possible in perimeter zones with the blinds continuously controlled to intercept direct sun rays