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Home arrow Engineering arrow Sustainable High Rise Buildings in Urban Zones: Advantages, Challenges, and Global Case Studies

Shading Devices

Regardless of the latitude, some form of solar shading is needed on east, west, and south sides of the building during the overheated period. Solar heat gain through windows can be reduced by sunshades, balconies, deep recesses, or sky-courts. Shading is also needed to reduce glare and direct daylight into deeper reaches of the floor-plate. Fixed shading devices are effective and not costly; yet it can block the sun during times when it is needed as a result of the time shift between the solar year and thermal year. Movable devices can overcome this problem by its flexibility and control to suit outside conditions. Movable louvers can provide additional protection against heat loss in the winter. Depending upon the season and time of the day, the angle control of the louvers achieves optimal daylight incidence in combination with minimal heat gain. Intelligent fa┬žades operate with automated angle control, regulated by incident radiation and outside air temperature.

Glazing Type

Clear glass is often preferred as it gives a more natural light into the inside. Tinted glass cannot be a substitute for sun shading. Tinted glass reduces thermal transmission to 20 %, which is still ineffective in hot climates. It has two negative effects: it conducts heat to inside space after it absorbs it and it reduces daylight significantly. Solar-reflective glass can be used to reduce solar penetration without affecting the view. However, it reduces both short-wave (heat) and long-wave (light) transmission, which results in reducing useful winter heat gain and natural light. It can be used though in climates where heat gain is not desired. Low emissivity glass reduces direct heat gain by transmitting a greater proportion of light than heat. It has the appearance of clear glass and is useful in situations where daylight is desired while solar heat gain should be minimized. It allows the use of larger glazing area for admitting daylight, without necessarily incurring an energy penalty. Other new intelligent glazing systems are currently being researched and some are available today such as photo-chromatics, phase-change materials, holographic, and electrically responsive glass. The green approach tends to encourage the use of clear or low emissivity glass.

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