Optimizing Benefits of Multiple-Slat Shading Device and High Performance Glazing on High-Rise Buildings

Abstract

The climate of Thailand is hot and humid and air-conditioning for thermal comfort is used in all tall buildings. Buildings with curtained walling are perceived to possess specific aesthetic value by many developers. As a consequence, such buildings cannot accommodate external shading device. In order to reduce transmission of solar radiation into such building, heat reflective glazing has been popularly used. Inadvertently, the building is subject to high cooling load from high heat gain through the curtained walling. However, as Thailand is located near the equator. For a northern or a southern façade, an exterior horizontal shading device can effectively shade radiation of the sun beam from a window below it while allowing skylight to enter the window to give a soft natural daylight in the room. The use of multiple-slat, sufficiently spaced horizontal shading device on the exterior of a facade on appropriately sized window will allow sufficient view out through the window, enables application of daylighting and reduces cooling load. This paper presents results of a study on the use of such shading device on windows under different combinations of glazing types, ratios of window area to wall area, and with un-insulated and insulated wall. When diffuse daylight from sky is used for daylighting, glazing that allows more daylight penetration is shown to offer a monetary worth of savings on electric lighting over its cost, and the cost of air-conditioning energy when the value of the ratio of window to wall ratio falls within certain range. The net benefit can be optimized at an appropriate ratio of window to wall area. When wall insulation is applied, the benefit is even enhanced at lower range of window to wall area.