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International Journal of Earth Sciences and Engineering 1 ISSN 0974-5904, Vol. 03, No. 01, February 2010, pp. 1-5 The influence of internal courtyard of Kerala traditional residential buildings in providing a comfortable indoor environment DILI A. S.*, NASEER M. A.**, ZACHARIA VARGHESE T.* * Departm...

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International Journal of Earth Sciences and Engineering 1 ISSN 0974-5904, Vol. 03, No. 01, February 2010, pp. 1-5

The influence of internal courtyard of Kerala traditional residential buildings in providing a comfortable indoor environment DILI A. S.*, NASEER M. A.**, ZACHARIA VARGHESE T.* *

Department of Civil Engineering, National Institute of Technology Calicut, Kerala, India ** Department of Architecture, National Institute of Technology Calicut, Kerala, India Email: [email protected], [email protected], [email protected]

Abstract: Traditionally, the built form of any region is derived for the beneficial aspect of the climate and to reduce the impact of unfavorable conditions. Kerala, the land on the southwest coast of India, has a characteristic Warm-Humid climate because of its geographic settings. The presence of high amount of moisture in the atmosphere for major part of the year causes thermal discomfort as there is less evaporation, resulting in perspiration. This becomes more acute in summer when the air temperature is close to or higher than the body temperature. In the traditional buildings of Kerala, which evolved through ages, the influence of internal courtyards is found to be highly effective in providing a comfortable indoor environment. The authors have conducted a smoke study to understand the influence of internal courtyard in inducing a constant and continuous air flow in traditional buildings of Kerala. This paper illustrates briefly the need for climate responsive design of buildings, the effect of internal courtyards in traditional buildings of Kerala and an investigation in a selected traditional building based on smoke study to analyze the flow of air through the interiors to achieve better thermal comfort. Key words: Kerala, Traditional architecture, climate, thermal comfort, courtyard, smoke study

Introduction Climate responsive design is the one that would provide a comfortable indoor environment in response to the seasonal variations of the climate at a particular place. Irrespective of the extreme climatic conditions that prevail outside, the building indoors should keep its occupants physiologically comfortable. This is achieved by means of passive control systems used in the building design. The modern architecture does not give due respect to passive and natural environment control measures as it goes along with modern materials, trends and technology which often cause high energy consumption. On the other hand, the traditional architecture at any place has evolved through ages by consistent and continuous effort to achieve more efficient and perfect solutions that are environmental friendly.

Kerala, a strip of land on the southwest coast of India lying between Arabian Sea on the west and Western Ghats on the east, has a warm-humid climate. The presence of high amount of moisture in the atmosphere along with higher air temperature for major part of the year is the characteristic of warm-humid climate. Under such climatic conditions, the physiological comfort can only be achieved by providing a constant and continuous flow of air through the interior of the building. The traditional architecture of Kerala is well known for its use of natural and passive methods in providing a perfect climate responsive design. The authors have been conducting experimental investigations to analyze the passive control methods of Kerala traditional buildings [Dili A. S. et al, 2009, 5 papers]. The internal courtyard provided in such traditional buildings is found to have a prime role in providing the required air movement through the building. Thus, in

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The influence of internal courtyard of Kerala traditional residential Buildings in providing a comfortable indoor environment

addition to the air flow measurement recorded with electronic sensors, a smoke study was conducted to analyze the internal air movement especially the air movement that is induced in the interiors of traditional buildings when there is still condition outdoors. The outcome of the study proves the efficiency of internal courtyard in climate responsive design of Kerala traditional architecture. Study of traditional buildings – the present status The modern practice in architecture lacks conscious effort in using passive methods of controlling the indoor environment. Excessive use of modern materials irrespective of their efficiency in regulating the indoor environment has often resulted in high energy consumption, leading to many environmental problems. There is a close connection between the energy use in buildings and the resulted environmental damage. This is because of energy intensive solutions that are required in buildings to attain comfort conditions in terms of mechanical cooling and ventilation and artificial lighting. This has caused severe depletion of nonrenewable energy resources and environmental degradation. Studies on passive environment control systems in buildings providing thermal comfort are in progress in the form of assessment of thermal comfort parameters of traditional buildings, in various part of the world [Youngryel Ryu et al, 2009, Mujgan Serefhanoglu Sozen et al, 2007, Do-Kyoung Kim et al, 2005, Lin Borong, et al, 2003 and Ryozo Ooka, 2000]. These types of studies were originated in Korea and Zambia in 1996 [Kyung-Hoi Lee et al, Steve Sharples et al, 1996, Albert Malama et al, 1997]. It was then attempted in different countries such as Japan, China, etc. within a short period. In other parts of India, the results of such studies have published recently in the context of N-E region [Manoj Kumar Singh et al., 2009]. The majority of these studies have precise aims to find out methods to adopt in modern buildings. The results of such

studies have been used recently in modern buildings in Korea [T.J. Kim et al, 2009]. Kerala traditional architecture, evolved based on the principles of climate responsive design, has now emerged as an important area among the researchers in this field. Efforts are made by researchers in this field for a comprehensive and quantitative analysis of traditional architecture of Kerala [Dili et al, 2009]. These studies undertaken in the context of Kerala have already started providing valuable results regarding the passive environment control systems. It is believed that the outcome of the research will provide the present day architects and engineers with energy efficient and sustainable design even while utilizing the modern materials and construction methods. The Effect of Internal Courtyards in Traditional Buildings of Kerala The basic module of a traditional Kerala residential building is nalukettu with four blocks generally rectangular or square in plan, built around an open courtyard. The blocks are topped with a sloping roof on four sides while the courtyard is open to sky for letting air and light inside (Fig.1). There is an internal verandah around the courtyard for protection from rain and sun. A typical layout of a traditional Kerala house is shown elsewhere [Dili et al, 2009].

Fig.1: A typical courtyard of a Kerala traditional residential building Courtyard and patio are quite common in warm humid climate where the building

International Journal of Earth Sciences and Engineering 1 ISSN 0974-5904, Vol. 03, No. 01, February 2010, pp. 1-5

DILI A. S, NASEER M. A and ZACHARIA VARGHESE T.

encloses an open space fully or partly [Krishnan et al]. Such spaces are commonly referred to as microclimate modifiers. They enjoy better microclimatic conditions than the surrounding open areas, and are supposed to have a positive effect on the indoor comfort conditions of the enclosing building volume. In a courtyard, a pool of cool air is retained as this is heavier than the surrounding warm air [Koenigsberger et al]. The top layer of the air in the courtyard gets warmer in day time and becomes lighter, causing the air to move upwards. Thus a low pressure develops in the courtyard and it induces an air movement from outside, through the surrounding spaces (Fig.2). In addition to this thermal induction, the internal courtyard helps to induce air movement due to pressure effect in the event of high velocity external wind that flow above the building. The wind flow reduces the pressure at the top layer of the air column and creates a suction effect above the small courtyard. This produces an upward movement in the top layer of air in the courtyard, pulling the air towards the court through the surrounding spaces resulting in circulation of air in those spaces.

Fig.2: Concept of air movement through courtyard

The internal space taken for the study is around the courtyard of 6 ft x 12 ft. The courtyard has an inward looking verandah of 3.5 ft width. The two sides of the courtyard are semi open spaces used for living and prayer. The other two sides are adjoined with rooms having windows opening to the courtyard. A plan and section with the selected area marked is given elsewhere [Dili et al, 2009]. The authors have devised and installed an instrumentation setup called Architectural Evaluation System (AES) in the building to monitor various climatic parameters continuously over a period of time. The inferences drawn from the field observations have already been published [Dili et al, 2009]. It was proved that there exists a continuous internal air movement irrespective of the flow of external wind. In order to understand the internal air movement better, especially under still-air condition, a smoke study was conducted. The smoke generated outside was allowed to pass through the building. The movement of smoke through various internal spaces of the building and the courtyard was then observed. These movements were then captured using high resolution cameras set at different locations within the building. It was observed that the smoke entered from outside to the internal spaces through the window openings and moved towards the courtyard to ultimately escape through the courtyard (Fig.3&4). Interestingly, it was also observed that when the smoke was put off, it disappeared from the building within seconds.

Smoke study The residential building selected for the smoke study is located in the northern part of Kerala at Nilambur in the Malappuram district. The building (Puthiya Kovilakam) is nearly 300 years old. The building has three courtyards of rectangular shape in which one courtyard is surrounded by a double storeyed structure. The other two courtyards are surrounded by single storeyed structures.

Fig.3: Smoke enters the building

International Journal of Earth Sciences and Engineering ISSN 0974-5904, Vol. 03, No. 01, February 2010, pp. 1-5

The influence of internal courtyard of Kerala traditional residential Buildings in providing a comfortable indoor environment

The study was conducted in the presence of external wind and also in the absence, i.e., when a still condition prevailed. The pattern of smoke captured clearly indicates that the movement is faster and the flow is turbulent in the presence of external wind due to the wind effect. The movement of smoke was slow but steady and the pattern of flow was laminar during the still condition. This clearly establishes that there exists a continuous convective flow through the building at all times as explained in the previous section.

Conclusion Natural and passive control of the indoor environment is an important aspect of traditional architecture of Kerala. The presence of internal courtyards has a prime role in achieving this comfort condition. The present study clearly establishes the influence of internal courtyard in inducing a continuous internal air movement to achieve thermal comfort in warm-humid climate even when still-air condition prevails outdoors. It is hoped that the methods and techniques thus adopted in the Kerala traditional architecture can be applied to the contemporary architecture of warm – humid regions. Acknowledgements

Fig.4: Smoke moves upwards from the courtyard

The authors extend sincere gratitude to Mr. Ravi Varma of Nilamboor Kovilakam for his kind cooperation for the conduct of the investigation.

References Discussion A continuous and constant air movement exists through the internal spaces and the internal courtyard of a traditional building irrespective of the external wind [Dili et al, 2009]. The smoke study conducted in the traditional building confirms this especially under still condition of external wind. This study establishes the influence of internal courtyard in inducing a continuous internal air movement thereby an effective passive control system for the thermal comfort of occupants in traditional buildings of Kerala. Arithmetical and experimental studies have reported that the airflow through windows drops down and then flows along the floor [Per Heiselberg, et al, 2001]. Since the windows are placed at a lower level (1 ft from floor) in traditional buildings of Kerala, this phenomenon helps the warm air from outside to interact with the cool air settled near the floor during its flow. This again makes the indoors cooler.

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International Journal of Earth Sciences and Engineering 1 ISSN 0974-5904, Vol. 03, No. 01, February 2010, pp. 1-5

DILI A. S, NASEER M. A and ZACHARIA VARGHESE T.

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International Journal of Earth Sciences and Engineering ISSN 0974-5904, Vol. 03, No. 01, February 2010, pp. 1-5...