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Case Study II: The Torrent Research Centre in Ahmedabad, by Abhikram.


Life building cost

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The Torrent Research Centre (Gujarat, India) is a complex of research laboratories with supporting facilities and infrastructures, located on the outskirts of Ahmedabad. This building uses Passive Downdraft Evaporative Cooling for a large scale office building and demonstrates that it is possible to achieve human comfort in dry hot regions without using regular HVAC systems and without compromising the cost of construction

Developed societies, with their sustained focus on the increasing importance of individuals, have made mechanical cooling an inherent necessity in any modern building in semi-arid regions of the world. Consequently, a majority of the buildings designed in such regions assume the use of artificial lighting and air-conditioning systems, even during daylight hours, for achieving human comfort conditions. For many years now, through our architectural practice, we have been trying to establish that such assumptions are a myth, in addition to being detrimental to the objectives of resource conservation, particularly for the developing countries like India.” Nimish Patel and Parul Zaveri.

SFA were appointed to give their inputs for one laboratory block. Allen Short visited Ahmedabad in May 1993 to understand the environmental conditions and evolve a preliminary concept of the building, using ground cooling as the primary approach. Since the temperatures at the appropriate depth under the ground were not found to be as low as required, this approach was abandoned in favour of the sealed evaporative cooling from the roof, with designated inlets and outlets for the movement of air. This approach is now known as the Passive Downdraft Evaporative Cooling (PDEC) method.

The design of the building facilitates generating an air draft, assuming still air conditions. The air heats up in the peripheral shafts, rises and escapes through the openings at the top. The air in this volume gets replaced from the usable spaces, which in turn receives its own replacement through the concourse area, on top of which the air inlets are located. The entering air is sprinkled with a fine spray of water mist at the inlet, during hot temperatures outside. This facilitates downdrafts. At each floor level, sets of hopper windows designed to catch the descending flow, can be used to divert some of this cooled air into the adjacent space. Having passed through the spaces, the air then exits via high level glass louvers openings which connect directly to the perimeter exhaust shafts towers that suck the air and create a circulation across the building insuring the displacement of fresh air along the day.

During the warm humid monsoon season when the use of the sprayed water would be inappropriate, the ceiling are brought into operation to provide additional air movement in the office and laboratories. In the cooler season the operating strategy is designed to control the ventilation, particularly at night, to minimise heat loss, this is done simply by the users adjusting the hopper windows and openings in their individual spaces to suit their requirements.

Overall control of the solar heat gain is achieved by judicious design of the glazing. The fixed windows are the only decided quantum and shaded externally, not only in the horizontal plane by overhangs, but also in the vertical one by the air exhaust towers which project from the façade. The buildings are thermally massive -the reinforced concrete construction framed structure has cavity brick infill walls, plastered inside and out, and the hollow concrete blocks filling the roof coffers, also plastered inside with vermiculite used as an insulating material on both roof and walls. External surfaces are white, the walls painted, the roof using a china mosaic finish.

Consequences:

The consequences of this major experiment have been under observation since the first occupation of the buildings, and will continue to be carried out for the coming years.

• In the summers, the inside temperatures have generally not exceeded 31°C to 32°C, when the outside temperatures have risen up to 44°C, a 12°-13°C drop

• The temperature fluctuations inside the building have rarely exceeded beyond 3°C to 4°C over any 24 hour period, when the temperature fluctuations outside were as much as 14°C to 17°C.

The economic viability of the project is demonstrated by the following indicators, which are computed for the total project, on the basis of the results from the buildings under observation.

• Additional civil works cost of the project including insulation etc. works out to about 12% to 13% of the civil works cost of a conventional building;

• Air-conditioning plant capacity saved, is about 200 M. Tonnes.

• The cumulative capital cost of the civil works and the A.C. plant works out to approximately Rs.50.0 lakhs more than the conventionally designed buildings.

• The annual savings in the electrical consumption including the savings on account of less use of artificial lighting during the day is approximately Rs.60.0 lakhs.

• The pay-back period of the additional capital cost, from the saving of the electrical consumption alone, works out to a little less than 1 year.

• The pay-back period for the cost of the construction of the entire complex, from the savings of the electrical consumption as well as plant replacement costs, works out to around 15 years.

In 2004-05, a Post Occupancy Survey was carried out by ‘Building Use Studies’ at the behest of University of Technology, Sydney, Australia & Victoria University of Wellington, New Zealand. This survey shows that the building, which was designed for 150-175 occupants, is still seen as adequately comfortable when the number of occupants has increased to more than 600, a 250 % increase. (see doc attached)

Conclusions:

•It is possible to make a difference in the human comfort conditions without having to depend on excessive use of electrical/ mechanical energy and with basic and elementary architectural systems.

•The process of achieving human comfort levels was based on the fundamental understanding that comfort condition is not dependant on absolute figures of parameters, but on the difference felt by the human skin, in the temperature and humidity conditions over a period of time.

•The process on the one hand minimized the impact of the external heat within the building through adequate measures of insulating the building’s external fabric, and on the other hand created an effective system of sealed evaporative cooling.

Through a detailed computation, an analysis of the costs of civil and air-conditioning works along with the electrical consumption was carried out for three options of systems to be used, viz: (a) the conventional building with air-conditioned/air-exhausted and open window areas; (b) the conventional evaporatively cooled building, through cooling pads in the inlets and fan driven ducted supply of air; and (c) the sealed evaporatively cooled building evolved by SFA. The analysis then showed a three years pay-back period for the additional costs from the savings in electricity cost.

«The Torrent Research Centre demonstrates excellent environmental outcomes. The findings of the post occupancy survey show that this building, completed over 10 years ago, continues to satisfy expectations for a contemporary workplace of high quality that is simultaneously energy efficient. While the wider implications of the success of such buildings for the Indian subcontinent where there is currently a large scale development of “glass boxes” that are both energy intensive and inappropriate for the climate, building performance outcomes in Torrent clearly reinforce the value of a climate responsive approach to building design in any location».

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Architects and Interior Consultants : Nimish Patel and Parul Zaveri, Abhikram, Ahmedabad, India

Environmental Consultants : Brian Ford , Short + Ford Associates, London, UK (Typical Laboratory Block) and CL Gupta, Solar Agni International, Pondicherry, India (Remaining Blocks)

Structural Consultant : Yogesh Vani Consulting Engineers, Ahmedabad, India

Utility Consultant : Dastur Consultant Pvt. Ltd., Delhi, India

Landscape Consultant : Kishore Pradhan, Mumbai, India

Lighting Consultant : Paresh Shah, Sukriti Design Incorporated, USA

Civil Contractors: Laxmanbhai Constructions (India) Pvt Ltd., MB Brothers Ltd., Shetusha Engineers and Contractors Pvt. Ltd., Materials Corner, JK Builders.

Project Period : 1994-99

Size : Built-up area is approximately 19700 m²

(All information provided is copyright © Abhikram, 2007. All rights reserved.)