New Approach in Designing a Kinetic Window Shading Using Optimization Methods

In the United States, commercial buildings consume 18% of the total primary energy, which is predicted to increase by 1.2% per year from 2006 to 2030 due to population and economic growth. Windows in commercial buildings are also responsible for 34% of commercial space conditioning energy use and 1.5% of total energy use in the United States. Therefore, controlling the heat gain and loss from windows in commercial buildings would save a significant amount of energy and subsequently reduce the carbon footprint. As the main function of shading is to moderate light rays, whether intercepting or allowing them to enter, having well-designed shading can improve building energy performance. However, shading should be designed carefully since decreasing the cooling load may result in increased heating load and vice versa. In addition, in designing window shading, achieving a balance between energy load reduction and light energy consumption is always challenging. This study proposes a new approach to designing kinetic exterior window shading for small commercial buildings, which changes the geometrical parameters of the exposed glazing area (EGA) of existing windows. To achieve this, first an optimization code was developed based on the hill climbing algorithm. The developed optimization code was then coupled with EnergyPlus software to determine the optimum area of the EGA, its optimum width to height ratio, and its optimum location in an existing window. To illustrate the application of the proposed shading and evaluate building energy performance a model was designed and presented in DesignBuilder software. The study showed the significant amount of energy saved by applying the proposed shading.