Lowtech solutions (2)

A second group of lowtech solutions is based on the physical phenomenon of reflection of solar radiation. Many solutions make use of radiative reflection:

1) solar shading: obviously well known as a measure to avoid summery overheating, but in fact a simple example of using radiative reflection to avoid solar radiation to enter the building. Most effective when applied at the outside of the building, because when the solar radiation has entered the building, it transforms into longwave radiation and glass is mainly opaque for longwave radiation. An interesting and neutral publication is Shading systems - Solar shading for the European climates. 

2) white and green roofs: traditionally flat roofs are black; they highly absorb the solar radiation, resulting in high surface temperatures up to 80-90°C. This causes higher conductive heat transfer to the inside of the building and contributes also to the urban heat island effect. White roofs reflect more (and thus absorb less) solar radiation, thus reducing the conductive heat transfer to the inside. Green roofs don't reflect so much the solar radiation, but the absorption of solar radiation causes extra evaporation of the water buffered in the green roof. An attempt to put the the impact of white roofs in the right perspective can be found here. An economic study of the environmental benefits of green roofs can be found here.

Guidance of daylight into a cave (Source: unknown)

3) daylight applications:
some of the most beautiful examples of use of radiative reflection can be found in some simple, but innovative daylight applications, such as cave lighting with daylight. A large database of daylight design examples can be found in the online Daylight Design Variations Book developed by TNO and TUE. They are all based on radiative reflection.

Source: Steven Holl

The most beautiful example of daylight application I know is the design by architect Steven Holl for the D.E. Shaw office building in New York. Although it looks like artificial coloured lighting, it is purely daylight. The 'secret' of this concept is explained here. It is worth analysing.