Integrating Visual and Energy Criteria for Optimal Window Design in Temperate Climates

Building codes and certifications require maximal building performance in different aspects. However, focusing on achieving a single purpose can prevent obtaining additional ones. This work aims to help building designers balance energy and visual performance design criteria. The difficulty to achieve many goals resides in high degrees of complexity when many building features must be considered in an infinite number of possible design solutions. Multi-objective optimization techniques start to be applied in building science, but different appropiate assessment criteria applied to a single problem can lead to diverse valid solutions. A brief review was made of commonly used energy consumption and visual comfort and performance criteria. The study was made through whole-building computer simulations of a standardized test room. This provided a solution space with "compromise sizes" satisfying both energy and visual aspect objectives. However, unprotected windows cannot meet all these criteria. This makes the provision of sun-protecting elements necessary. A selection procedure based on design needs is detailed.