  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.
