Windows combined with a heat source (e.g. a fireplace) are one of the oldest methods of achieving thermal comfort in buildings during cold periods. Today the simplest way to achieve thermal comfort is to install a system that can adjust the parameters. Most houses have a heating system installed and, in warm climates, possibly a cooling system. However, windows can cool down a building on a warm summer day.
Draught and temperature asymmetry can be caused by windows, as mentioned earlier. It can be difficult to determine whether the sensation of coldness is caused by draught from the windows or by cold radiation. A leaky window can be fixed by replacing the gasket and/or pane – or the whole window could be replaced. To some extent, cold radiation can be limited with the use of an internal blind that will increase the inside surface temperature.
3.4.1 Blinds and shutters
Blinds and shutters block solar radiation and thus reduce the amount of heat entering a room. Overheating during summer can be efficiently reduced, and even eliminated, by the use of proper solar shading. It can also improve the thermal insulation of windows in winter. This can reduce thermal discomfort from cold radiation and temperature asymmetry. Even better, when applied at night, this extra insulation can decrease the demand for heating. In terms of energy, shading should only be used at night during winter, because the solar gains are often of greater importance than the heat loss (see section 5.6.3).
Example: solar shading reduces experienced temperature for different glazing and accessories under strong solar radiation.
The measured values are the results of a small experiment. The operative temperature was measured behind a glass unit with different shading accessories to illustrate the effect of different types of shading.