Basic info is found in Chapter 5.
Snow is a light material that consists mainly of small air spaces; it is therefore a good insulator. The thermal insulation of dry snow is equivalent to that of rockwool, and this is reduced with increased water content.
Over large areas in Northern Europe, dry snow settles every winter and remains for about six months, helping with roof insulation just when it is most needed. So it is clear that this snow should be conserved. There are six ways of retaining snow on a building:
• A sloping roof of not more than 30°, preferably less.
• A roof covering made of high friction material, such as grass.
• A snow guard along the foot of the roof.
• An unheated space under the roof, or else very good roof insulation.
• Windbreaks in front of the roof.
• Reduced solar radiation on the roof, for example a single pitched roof facing north.
Some of these conditions have disadvantages. But snow is free, and it is an efficient and environmentally friendly insulating material. The thermal insulation of snow should certainly be considered when designing in areas where white winters are common. However, these regions look set to dwindle as a result of global warming. Regions with mild winters and few snow days do not need snow planning; the same goes for sites exposed to heavy wind, but in many cases well-planned placing of snow drifts can provide excellent protection from wind. This can be done using special snow fenders with an opening of approximately 50% in the grid, and also with the help of planted hedges and avenues. Snow will settle on the lee side in areas of turbulence.
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