Evaluating window systems for decision support regarding the balance of daylight and heat gains

Designing windows requires dealing with the external environmental conditions, which may be conflicting, such as solar gains and daylight. This paper evaluates the performance of different alternatives for window systems to support design decisions on the balance of light and heat gains in the indoor environment, focusing on offices in a hot and humid climate. In order to do this, integrated computer simulations using the Daysim and EnergyPlus softwares were performed, considering the activation of electric lighting only when daylight was not sufficient to meet the usage requirements. The variables were window-to-wall ratio, glazing type and shading angle, simultaneously. Compromise solutions were found regarding the criteria of availability and uniformity of daylight and electricity demand in the indoor environment. It was observed that solar control through the use of shading devices presented substantially better results than solar control by reducing transmission of solar radiation by the glass. The assessment conducted contributes to increase understanding about the impact of different design variables on the phenomena characterising the performance of fenestration systems.