Influence of window recess on solar loads, heat loss and external condensation

The current architectural preference for the recess of windows is in line with the forefront of the building facade. The recess of a window has consequences for: solar loads, heat loss, and risk of outside condensation. This paper presents an analysis of these issues in relation to variations in recess depth and differences in orientation of the window. The solar load in buildings is highly influenced by the depth of the window recess, depending on the orientation. Solar gains both contribute to heating the building during the heating season, but also to overheating in other periods. The latter being especially important for other buildings than residential buildings. This is analysed for different window orientations and size (height and width) as wells as the recess depth. Recess depth also influences the overall heat loss though the facade and window and is analysed through detailed calculations. Last, but not least, condensation on the external face of modern low energy windows causes a serious issue regarding visual comfort in the mornings during periods with clear weather and low outdoor temperatures. Analyses of the recess depth influence on the outside condensation risk is presented. The issues regarding the recess depth for facade windows is analysed using dynamic simulations of different window and recess depths in different orientations in combination with 2D static calculations of the overall heat loss coefficient for the total window and facade construction in typical highly insulated facade constructions.