Issues in Window Selection: Human Factors

Daylight | Glare | View | Thermal Comfort

View

View is the most subjective of the attributes in this analysis. Nevertheless, it deserves attention since it is a desirable characteristic in workplaces and is clearly influenced by window design and selection. Research has shown that window size, shape, proportion, and view content greatly influence human perceptions such as spaciousness as well as the attractiveness and acceptability of the window (Al-Sahhaf 1987). In this analysis, the focus is on the attributes of the window itself-shape and content issues are left to the designer.

The view index devised for this analysis results from multiplying the following factors: window area, the visible transmittance of the glass, the fraction of window area not obstructed by permanent exterior shading devices (overhangs and fins), and the percentage time that interior shades do not obstruct the view. A final factor is designed to lower the view index for windows that cause interior reflections when interior light levels are low. With the resulting index factor, a higher number is better. The view index does not take into consideration the potentially significant effects of the shape of the window, or that view blockage through artfully subdividing or intersecting a window by a building structural element may actually enhance the window's appeal to the viewer. Nor does the view index take glass color into account, although research suggests that the more strongly monochromatic transmitted window light becomes, the less acceptable it is in rendering the interior (Cuttle 1979).

Figure 2-41 indicates the view index for nine window types under different shading conditions. With no exterior shading devices and a constant window area, the window visible transmittance (VT) has the strongest influence on the view index. Window D with a very low VT has the lowest view index. With exterior shading devices, all view indices are reduced substantially.