Choosing solar shading
Bizarrely, it is the back cover of Solar Shading of Buildings* that shows what it has to offer. It begins with a few pages on 'why shading?' and principles, but is generally a good attempt at systematic comparison of solar shading approaches - from external to internal. Those subject to measurement and simulation are:
external - canopies, light shelves, fixed and moveable louvres
glazing - tinted, low-emissivity, films
reducing window area
mid-pane devices - blinds, louvres
internal shading - curtains, venetian blinds, fabric blinds, reflective roller blinds.
Each of the above are summarised in a standard format:
what they're recommended for, for example, south-facing windows, where glare is a problem
their total solar transmission for a south-facing window compared with clear double glazing
the worst-case scenario of overheating. The figures can only be used as a rough indicator, especially as systems perform differently at other orientations
solar transmittance compared with clear double glazing
Each system also has a brief commentary on practical performance, such as noting recent developments in heat-mirror low-emissivity coatings. More could have been said about user-control.
For each system type there is also brief commentary on performance systems less used in the uk, like external shutters and roller blinds, and on recent technologies such as photochromics and prismatic glazing.
Despite this variety, some clear conclusions are drawn, for example that only sophisticated louvre systems can really control both solar gain and glare. Otherwise hybrids of two or more systems are likely to be needed.
* 'Solar Shading of Buildings'. Paul Littlefair. bre Report br 364. crc, 0171 505 6622. 30pp. £40 + 10 per cent p&p. (aj readers post-free.)