A parametric study on window-to-floor ratio of double window glazing and its shadowing using dynamic simulation

When incorrectly designed, windows can be responsible for unnecessary energy consumption in a building. This may result from its dimensions, orientation and shadowing. In a moderate climate like the Portuguese, and considering an annual thermal comfort assessment of a space, if windows are under-dimensioned or over-shadowed, they can contribute to the increase of heating needs. However, when over-dimensioned or under-shadowed, they contribute to the increase of cooling requirements. Therefore, it is important to find the optimum design that balances orientation, dimension and shadowing, contributing to minimize both the heating and cooling needs. This study presents a parametric analysis of a double glazing window in its orientation and dimension, located in the Portuguese city of Coimbra. For each window orientation and dimension, the optimum overhang depth is determined. The objective is to minimize degree-hours of thermal discomfort. Results show that overhangs are mainly a corrective mechanism to over-dimensioned openings, thus allowing that building practitioners may choose a wider range of windows dimensions.