Optimisation of a daylight-window: hospital patient room as a test case

In a healthcare environment a window is necessary to transmit daylight and provide outside view to enhance therapeutic performance. However, a window impacts on several environmental attributes of the indoor space. Depending on the size, orientation and solar shading configuration, a window influences on visual and thermal comfort, as well as on the energy consumption of the building. It is thus necessary to optimise window design for maximum performance. Computer modelling and simulation techniques integrated with optimisation methodologies offer opportunities to evaluate design decisions considering various criteria. In this study a patient room window has been evaluated using computer modelling and simulation. The aim of the study was to demonstrate an integrated opitimisation methodology to identify the optimal design of a window considering daylight and thermal performances at the early stages. The window comprised a tall pane of glass and a light shelf, and was oriented toward the South. Four parameters were used to define the window: the width, sill and lintel level heights, and the depth of the solar shading. Performance of the window was measured for variable parametric values based on daylight factor and annual cooling/heating loads in the room. The study demonstrates a novel approach of optimising window configuration for daylight design using parametric computer simulations and evaluates the potential and limitations of the technique in daylighting design.