Friday 15 February 2013

Author(s): Anupam Chakravartty

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  • Thanks for this wonderful

    Thanks for this wonderful article. I wish more architects, and developers would think green for the environment and not green as in money..

    Posted by: Anonymous | 3 years ago | Reply
  • This is indeed a wonderful

    This is indeed a wonderful development in our country and we learn about it thanks to CSE. Recent scientific research on mind-body connection has encopmassed areas such as recovery of patients when they are in better contact with nature. It's being pursued very systematically. For example, trials such as comaprison on recovery of patients when they stare at the regular white wall of the hospital compared to looking at a beauiful landscape on a digital window vs being able to peep out of a real window to look at a tree or a garden outside have proved that recovery rates are faster when they are in contact with natural surroundings. For more related information on subtle positive effects of being with nature, you may refer to the work of Foundation for Contemplation of Nature at the above mentioned website.

    Posted by: Anonymous | 3 years ago | Reply
  • Excellent article. The West

    Excellent article.

    The West spends most of the energy on heating while sunbelt countries on cooling. There is a saying, ÔÇ£ Banyan tree shade,well water and Brick Houses are cooler in summer and warmer in winter."

    There is the need to revive the traditional methods of house construction improving with modern techniques. Studies have shown that the application of all the above techniques in buildings may decrease their cooling load up to 50% - 70%. Generally, concern for energy consumption is only marginal in the majority of architectural-design practices, even in the developed countries. Passive solar energy-efficient building design should be the first aim of any building designer, because, in most cases, it is a relatively low-cost exercise that will lead to savings in the capital and operating costs of the air-conditioning plant. In todayÔÇÖs architecture, it is now essential for architects and building engineers to incorporate passive cooling techniques in buildings as an inherent part of
    design and architectural expression and they should be included conceptually from the outset. Incorporation of these passive cooling techniques would certainly reduce our dependency on artificial means for thermal comfort and minimize the environmental problems due to excessive
    consumption of energy and other natural resources and hence will evolve a built form, which will be more climate responsive, more sustainable and more environment friendly.

    Passive cooling of buildings:
    A ÔÇÿpassiveÔÇÖ solar design involves the use of natural processes for heating or cooling to achieve balanced interior conditions. The flow of energy in passive design is by natural means: radiation, conduction, or convection without using any electrical device. Maintaining a comfortable environment within a building in a hot climate relies on reducing the rate of heat gains into the
    building and encouraging the removal of excess heat from the building. To prevent heat from entering into the building or to remove once it has entered is the underlying principle for accomplishing cooling in passive cooling concepts. This depends on two conditions: the availability
    of a heat sink which is at a lower temperature than indoor air, and the promotion of heat transfer towards the sink.

    Environmental heat sinks are:
    Outdoor air (heat transfer mainly by convection through openings)
    Water (heat transfer by evaporation inside and / or outside the building envelope)
    The (night) sky (heat transfer by long wave radiation through the roof and/or other surface adjacent to a building
    Ground Passive cooling techniques can reduce the peak cooling load in buildings, thus reducing the size of
    the air conditioning equipment and the period for which it is generally required.

    Here are some of the Passive Cooling Techniques adopted in Designing Big Buidings:
    Shading by overhangs, louvers and awnings etc.
    Shading of roof
    Shading by trees and vegetation
    Shading by textured surfaces
    Induced ventilation techniques:
    Solar chimney
    Air vents
    Wind tower
    Radiative cooling
    Diode roof
    Roof pond
    Evaporative cooling
    Passive downdraft evaporative cooling (PDEC)
    Roof surface evaporative cooling (RSEC)
    Earth coupling
    Earth air tunnel
    Earth berming
    Desiccant cooling

    The design of old houses(mud) in Rajasthan is a fine example of passive cooling.

    In hot climates it is necessary to adopt measures to lower the average indoor temperature to a level below the outdoor. Specially designed mud walls are still poplar in the hamlets (Dhanies) of western Rajasthan to deflect the hot winds. These are some of the conventional methods of passive cooling, typical in hot and dry climatic condition. India has a very diversified climate heating of buildings in also required especially in upper latitudes and hilly areas and cooling of buildings is required in lower latitude and desert areas. Solar passive architecture provides proper orientation and design of fenestration i.e. doors and windows to take maximum advantage of sun and wind. For heating the aim is to admit the sun's energy as much as possible and to reduce he loss of heat in the nights. This is achieved by direct gain through windows, therm-wall, or solarium and other such means. The heat loss is minimized by the proper design of walls, by insulation of walls and roof, by night insulation on windows, by double glazing of window- etc.

    In this connection the design of East Gate Centre,Harare,Zimbabwe needs to be considered for adoption.

    The Eastgate Centre is a shopping centre and office block in central Harare,Zimbabwe whose architect is Mick Pearce. Designed to be ventilated and cooled by entirely natural means, it was probably the first building in the world to use natural cooling to this level of sophistication. It opened in 1996 on Robert Mugabe Avenue and Second Street, and provides 5,600 m┬▓ of retail space, 26,000 m┬▓ of office space and parking for 450 cars.

    The Eastgate Centre's design is a deliberate move away from the "big glass block". Glass office blocks are typically expensive to maintain at a comfortable temperature, needing substantial heating in the winter and cooling in the summer. They tend to recycle air, in an attempt to keep the expensively conditioned atmosphere inside, leading to high levels of air pollution in the building. Artificial air-conditioning systems are high-maintenance, and Zimbabwe has the additional problem that the original system and most spare parts have to be imported, squandering foreign exchange reserves.

    Mick Pearce, the architect, therefore took an alternative approach. Because of its altitude, Harare has a temperate climate despite being in the tropics, and the typical daily temperature swing is 10 or 14 ┬░C. This makes a mechanical or passive cooling system a viable alternative to artificial air-conditioning.

    Passive cooling
    Passive cooling works by storing heat in the day and venting it at night as temperatures drop.
    ÔÇó Start of day: the building is cool.
    ÔÇó During day: machines and people generate heat, and the sun shines. Heat is absorbed by the fabric of the building, which has a high heat capacity, so that the temperature inside increases but not greatly.
    ÔÇó Evening: temperatures outside drop. The warm internal air is vented through chimneys, assisted by fans but also rising naturally because it is less dense, and drawing in denser cool air at the bottom of the building.
    ÔÇó Night: this process continues, cold air flowing through cavities in the floor slabs until the building's fabric has reached the ideal temperature to start the next day.

    Passively cooled, Eastgate uses only 10% of the energy needed by a similar conventionally cooled building. 1
    Eastgate is emulated by London's Portcullis House (2001), opposite the Palace of Westminster. The distinctive giant chimneys on which the system relies are clearly visible.
    Modern use of traditional solutions to work well, the building must be very carefully designed. After computer simulation and analysis, the engineering firm Ove Arup, gave Pearce a set of rules.

    They said that no direct sunlight must fall on the external walls at all and the north façade [direction of summer sun] window-to-wall area must not exceed 25%. They asked for a balance between artificial and external light to minimize energy consumption and heat gain. They said all windows must be sealed because of noise pollution and unpredictable wind pressures and temperatures, relying on ducted ventilation. Above all, windows must be light filters, controlling glare, noise and security.

    To help with this last, the windows have adjustable blinds, but Pearce also used deep overhangs to keep direct sun off windows and walls. Deep eaves are a traditional solution in Africa, shading the walls completely from the high summer sun, while allowing the lower winter sun to warm the building in the morning.

    Further, passive cooling systems are particularly appropriate for this part of Africa because, long before humans thought of it, passive cooling was being used by the local termites. Termite mounds include flues which vent through the top and sides, and the mound itself is designed to catch the breeze. As the wind blows, hot air from the main chambers below ground is drawn out of the structure, helped by termites opening or blocking tunnels to control air flow.

    Pearce's practice is in Harare, and he specialises in buildings which are low cost, low maintenance, and have low environmental impact. His projects try to make best use of locally available resources, and include Harare International School Arts Centre, Harare Hindoo Temple and Chinhoyi Provincial Hospital, Zimbabwe.

    Dr.A.Jagadeesh Nellore(AP),India

    Posted by: Anonymous | 3 years ago | Reply
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