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Solar Shading System Based on Daylight Directing Glass Lamellas

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The overheating problems in office buildings must be solved with efficient solar shadings in order to reduce the energy demand for cooling and ventilation. At the same time the solar shading should not reduce the daylight level in the building on overcast days because it would result in a lower visual comfort level and increased energy consumption for lighting. The paper describes a new type of solar shading system based on dynamic lamellas made of solar control glass with high reflectance coating which reduces the solar gain on sunny days and at the same time is able to redirect some of the daylight further into the back of the room where it is needed on overcast days. Measurements of the daylight performance were carried out on a full scale model of the solar shading system in SBi’s Daylight Laboratory. The results show that the shading system under overcast conditions reduces the daylight factor close to the façade while it is unchanged or even higher in the back of the room. Under sunny sky conditions the daylight level is reduced in the office. Compared to traditional solar shading systems with less transparent or opaque lamellas the proposed solar shading system yields a higher daylight factor improving the distribution and exploitation of daylight in the office and furthermore it gives a less obstructed view out. Calculations show that the new system reduces the energy demand for cooling and ventilation when it is used as a traditional solar shading device and furthermore the energy demand for lighting is reduced when the glass lamellas are rotated for redirecting the daylight further into the room.