Energy performance for external shadings

In Figure 9.6.5, examples of g-values for external shadings in combination with a triple-glazed window (with argon and two low-e coatings of 4 per cent) are shown. This window has a centre-of-glass U-value of 0.69 W/m2K. The window is facing south in a cold climate. The window is 1.2 m x 1.2 m and 0.9 m above the floor. The awnings are projected 70 cm down and 70 cm out from the window; thus, the awning angle is 45°. The awnings are 15 cm wider than the window on each side in order to increase efficiency.

For this example, fully closed grey blinds, a beige screen, grey blinds of 45° and a dark awning are the most effective from spring to autumn. The colour of the awning is important. As can be seen, the window with a blue awning has a g-value of approximately 9 per cent during the summer period. The window with a beige awning has a g-value of 16 per cent during the same period.

A horizontal slatted baffle is not a good choice. The slats are horizontal in this example. This baffle gives a similar shade as a roof overhang or a balcony above a window. Since a baffle or overhang is not retractable, it will also shade the window during early spring and late autumn. A 1 m overhang is more effective than only 0.5 m. But to increase the overhang to more than 1 m is not effective in this climate.

Figure 9.6.6 shows the corresponding performance for a westerly orientation in a cold climate. Here it can be seen that horizontal shading - for example, a slatted baffle - results in poor performance. Vertical shadings are not as influenced by the orientation. They are, therefore, preferable for west or east orientations.

The corresponding performance for the temperate climate (Zurich) is shown in Figures 9.6.7 and 9.6.8. During wintertime, the sunshades are more effective in the temperate climate for a south orientation. However, during the summertime, they are slightly more effective in the cold climate except for the beige screen and fully closed Venetian blinds. For a westerly orientation, the sunshades perform somewhat better in the temperate climate.

Figures 9.6.9 and 9.6.10 show the corresponding performance for the mild climate. The performance is almost the same as for the temperate climate.

Source: Maria Wall

Figure 9.6.5 Monthly mean g-values for the combination of window and exterior shading: Triple-glazed window with argon (12 mm) and 2 low-e coatings (4 per cent); south orientation in a cold Stockholm climate

Source: Maria Wall

Figure 9.6.6 Monthly mean g-values for the combination of window and exterior shading: Triple-glazed window with argon (12 mm) and 2 low-e coatings (4 per cent); west orientation in a cold Stockholm climate

Source: Maria Wall

Figure 9.6.7 Monthly mean g-values for the combination of window and exterior shading: Triple-glazed window with argon (12 mm) and 2 low-e coatings (4 per cent); south orientation in a temperate Zurich climate

Source: Maria Wall

Figure 9.6.8 Monthly mean g-values for the combination of window and exterior shading: Triple-glazed window with argon (12 mm) and 2 low-e coatings (4 per cent); west orientation in a temperate Zurich climate

Source: Maria Wall

Figure 9.6.9 Monthly mean g-values for the combination of window and exterior shading: Triple-glazed window with argon (12 mm) and 2 low-e coatings (4 per cent); south orientation in a mild Milan climate

Source: Maria Wall

Figure 9.6.10 Monthly mean g-values for the combination of window and exterior shading: Triple-glazed window with argon (12 mm) and 2 low-e coatings (4 per cent); west orientation in a mild Milan climate

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