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

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Conclusion

I t is apparent that large-scale commercial buildings such as office buildings are more exposed than other types of buildings to the full impact of external temperatures, wind, and solar radiation. Also, these buildings have a great effect on heat islands generated in urban environments. Architectural design decisions that have great impact on building energy such as orientation and built form configuration are made at the early stages of the design process. Prioritizing design issues and making the right decisions at this early stage is very crucial. This chapter derived sustainable design guidelines (see Appendix A) from previous published research and used them as basis for analysis and evaluation of existing cases. The guidelines shown in Appendix A should be used in combination with the design issues and determinants shown in Table 3.2.

Appendix A: Guidelines for Sustainable Tower Architectural Design

A. Built form configuration

A1. Orientation

The long axis of the built form should be oriented east-west so that the long side of the building faces north and south

This allows to design the majority of the windows into the north and south walls and accordingly to reduce solar heat gain

A2. Aspect ratio

As a general rule of thumb, the optimum aspect ratio of the built form should be as 1:2-1:3 for climatic zones nearer to the equatorial zone and lesser at the higher latitudes

B. Arrangement of the building masses

In arid and tropical regions, the service cores of the building should be located on the east and west sides of the building, so as to help shade its form from the low angles of the sun during the major part of the day

Studies show that double-core configuration, with window openings running north and south and cores on the east and west, can achieve significant savings in air-conditioning The advantage of using this placement is to reduce solar heat gain into the internal user spaces and provides a thermal buffer zone to the hot sides, while at the same time maximizing heat loss away from user spaces

C. Floor-plate design

C1. Position on the site and relation to sun and wind

The floor-plate strategy is about the relationship of the building’s floor plate shape, its position on the site, and its orientation to the sun’s path and wind direction

(continued)

C2. Floor-plate shape

In hot arid and tropical climates, the optimum shape is a rectangle that minimizes the length of east and west sides while maximizes that of north and south sides, to reduce solar insolation on wider sides

The internal spaces arrangement should be planned to reduce solar gain into high occupancy spaces while service spaces can be used as solar buffers

D. Building skin design

The green approach does not recommend using hermetically sealed skins. The ideal building skin is the one that is environmentally responsive filter, which has to be multi-functional:

• Reduces solar heat gain to the internal space through external shading

• Maximizes the use of daylighting, provides fresh air ventilation

• Serves as acoustic barrier, and contributes to the building’s esthetics

Its permeability to light, heat, and air and its visual transparency must be controlled with flexibility of modification, so that the building can react to changing local climatic conditions

E. Shading devices

Solar shading is needed on east, west, and south sides of the building, especially during the overheated period. Shading by light shelves can help to reduce glare and direct sunlight into deeper reaches of the floor-plate

Fixed shading devices are effective and not costly. Movable devices are more expensive, but provide high flexibility and control to suit outside conditions. Depending upon the season and time of the day, the angle control achieves optimal daylight incidence in combination with minimal heat gain

Intelligent fagades operate with automated angle control, regulated by incident radiation and outside air temperature

(continued)

F. Glazing

Clear glass is often preferred as it gives a more natural light into the inside. Tinted glass has two negative effects: it conducts heat (approx. 80 %) to inside space after it absorbs it and it reduces daylight significantly

Low-e 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. The green approach encourages the use of clear or low emissivity glass

Other new intelligent glazing systems are currently being researched and some are available today such as photochromatics, phase-change materials, holographic, and electrically responsive glass

G. Natural and artificial lighting systems

Objective: to enhance the quality of indoor spaces and cut energy consumption through optimizing the use of daylighting and minimizing the need for artificial lighting

Adequate daylight can easily be introduced up to 4.6 m (15 ft) with conventional height window. New technologies can passively redirect sunlight to larger depths (4.6-9.1 m,

15-30 ft); i.e., holographic optical elements, articulated light shelves, and light pipes

Narrowing the width of floor plate to approx. 14 m can help to reduce artificial lighting and optimize natural lighting

 
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