Patent ID: 8881456

Claim:
A shading device for a building, comprising: a chamber formed between a sheet of glass adjacent to the interior of the building and a sheet of glass adjacent to the exterior of the building; a blind having a plurality of slats installed inside the chamber; an actuating device, wherein the actuator rotates the plurality of slats, wherein each of the plurality of slats has two opposite sides, and at least one of the slats has one side having a low reflectivity coating and the other side having a high reflectivity coating, wherein one of the two sheets of glass has a low emissivity film on a surface facing the chamber, wherein the actuator is controlled by a central processing unit, the central processing unit is configured to calculate a solar elevation angle and is configured to control the actuating device to rotate the plurality of slats to an angle, wherein the solar elevation angle is calculated to according to the following equation: sin hs =sin δ·sin φ+cos δ·cos φ·cos ω wherein hs represents the solar elevation angle, δ represents a solar declination, which equals {(90±23.5)−altitude−y*0.25} wherein y refers to a number of days apart from the Summer Solstice or the Winter Solstice φ represents a local altitude, ω refers to solar hour angle which is 0° at a local high noon, negative in forenoon at −15° per hour away from the local high noon, and positive in afternoon and +15° per hour away from the local high noon.