By careful site planning and screening with fences, trees and hedges the amount of wind reaching the building envelope can be much reduced. If the average wind speed around a building is reduced by 1 m/s, this alone can reduce the energy requirements for space heating by 3%. In the Norwegian coastal town of Kristian-sund, where the average wind speed is 22 km/h (Beaufort scale 4), the loss of heat for an unscreened building through infiltration is 40% greater than for a screened building.
There are several available constructive means to reduce the infiltration of wind into the main body of a building:
• Wind breaking structures.
• Wind breaking textures.
Wind breaking structures
A windbreak structure should be perforated and preferably be on battens at a distance from the actual wall. By using about 30% perforation, a minimal difference of pressure between the front and the back of the screen is achieved. The formation of eddies is thus reduced, so that wind and rain are effectively slowed down. Suitable materials include climbing plants, trellises, timber battens or metal ribbing.
A wind breaking texture is mounted directly on the main wall, in the form of a rough-structured surface that causes countless minute air movements-a sort of air cushion. The wind is stopped dead instead of penetrating further into the wall. Effective materials for this are roughly-structured render, cladding made of branches or a living surface of plants, including conventional creepers.
Neither external windbreaks nor texturing has any effect on air infiltration as a result of suction forces. The wind protection, therefore, needs to be complemented by a wind barrier in the outer layers of the wall construction itself. This is normally behind the external cladding and is itself ventilated. Suitable materials include exterior quality plaster-boards, boards of wood fibre, and various papers or asphalt impregnated sheeting.
To this, sealants and mastics around windows, door openings and other joints have to be added. These latter products are often plastics-based, hence oil products, and may have far more limited lifespans than is often assumed. This is especially the case on south facades where they are exposed to solar radiation and large diurnal temperature variations. These joints are often difficult to inspect or improve. The best solution is to avoid the need for these as far as possible through careful cutting and fixing of the building elements - good carpentry - and by having overlaps in the wind barriers that are fixed tightly with small battens.
Wind barriers should not let through air more than 0.1 m3/m2 with a pressure of 10 Pa. In extremely windy conditions such as heavy storms or hurricanes, it is very difficult to prevent wind penetrating the building. In exposed locations it would be best to use heat insulation materials with good wind-proofing properties as well, e.g. well-compressed loose-fill wood fibre.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.