Protection of buildings against overheating
In warm seasons buildings are generally overheated due to sunshine penetrating through the glazed surfaces. In such periods glazed surfaces must be protected against solar rays. In temperate climate the universally accepted limit of thermal comfort is 22°C air temperature. This value is considered as the threshold temperature of shading. Above this the penetration of any energy must be hindered through glazed surfaces in order to avoid the overheating of the indoor space. The threshold temperature of shading will differ in time according to climatic regions and its duration my also differ from one, to several days. By using meteorological data one can determine the date and time of the local shading threshold. These data can be visualized on the solar chart.
The SunArch program based upon recorded temperatures provides shading threshold data of 22°C for four meteorological regions, for periods of one, three and six days. By marking the date and hours on the corresponding sun path diagram, knowing the actual meteorological facts referring to the period in question, one may study to what grade the space under study will be overheated. On the figure above one can state the precise date and time - by means of the sunpaths appearing within the border of our window - when the solar rays will reach the glass. In the same time the statistical probability of the one, three or six days occurrence of the 22°C air temperature can also be stated.
With the help of the SunArch program one may present the sunpath diagram referring to the site under investigation. The diagram, may be presented in projection, as it is shown on the upper figure, but it may also be presented in aerial view shown below. In case of our aerial view the horizon and the sky above it with the sun paths, clock lines and geographic longitudes can be rotated and inclined thus providing a more favourable position for examination.
Other abstracts:
- Solar energy impact by orientation
- Maximum solar energy produced by the proper orientation of collectors
Last modification: 28. May 2008.