Passive environment control system of Kerala vernacular residential architecture for a comfortable indoor environment: A qualitative and quantitative analyses PDF

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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/223495691 Passive environment control system of Kerala vernacular residential architecture for a comfortable indoor... Article in Energy and Buildings · June 2010 DOI: 10.1016/j.enbuild.2010...

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Passive environment control system of Kerala vernacular residential architecture for a comfortable indoor... Article in Energy and Buildings · June 2010 DOI: 10.1016/j.enbuild.2010.01.002

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Energy and Buildings 43 (2011) 653–664

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Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild

Passive control methods for a comfortable indoor environment: Comparative investigation of traditional and modern architecture of Kerala in summer A.S. Dili a,∗ , M.A. Naseer b , T. Zacharia Varghese c a b c

Department of Architecture, TKM College of Engineering, Kollam, Kerala, India Department of Architecture, National Institute of Technology Calicut, Kerala, India Department of Civil Engineering, National Institute of Technology Calicut, Kerala, India

a r t i c l e

i n f o

Article history: Received 15 July 2010 Received in revised form 19 September 2010 Accepted 5 November 2010 Keywords: Kerala Traditional architecture Modern building Indoor environment Summer

a b s t r a c t Scientific investigation on traditional architecture of Kerala, that is known for its use of natural and passive methods for a comfortable indoor environment, has been revealing remarkable results recently. Qualitative analysis of the passive methods adopted in traditional buildings and detailed quantitative investigation carried out during all seasons to evaluate thermal comfort have already been reported. As a step ahead, in order to understand the performance of traditional building in comparison with that of modern building, a field study was conducted simultaneously in a selected traditional and a modern residential building during the most unpleasant summer period. The study was conducted by continuously monitoring the indoor and outdoor conditions of both the buildings using a custom made instrument called “Architectural Evaluation System”. The results reveal that an efficient passive and natural control system exists in Kerala traditional architecture in providing a comfortable indoor environment irrespective of the outdoor climatic conditions. © 2010 Elsevier B.V. All rights reserved.

1. Introduction The main purpose of a building is to provide an environment that is comfortable, and spoils neither the health nor performance of its occupants [1]. A good indoor environment is important to the success of a building, not only because it will make its occupants comfortable, but also because it will decide its energy consumption and thus influence its sustainability in terms of energy [2,3]. The role of passive controls in reducing the need for high-energy solutions has become important during today’s energy-economic crises [4]. Natural and passive cooling method for buildings, can improve indoor environment quality, provide thermal comfort, and reduce energy consumption in buildings. As a result, the study of natural and passive methods for controlling indoor environment has gained more and more attention in recent years [5]. The energy savings using passive and traditional techniques in houses for the purpose of maintaining thermal comfort in comparison with modern techniques are established in many investigations [6–9]. Moreover, the trend towards more efficient architectural designs is pausing challenges to the engineers to provide healthy low-energy design solutions [10,11]. The indoor environment in naturally ventilated buildings greatly depends on the local climate and the way environmental

∗ Corresponding author. Tel.: +91 944 7303875; fax: +91 474 2712023. E-mail addresses: dili [email protected], [email protected] (A.S. Dili). 0378-7788/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.enbuild.2010.11.006

controls are used [12–14]. The building’s characteristics influence the impact of outdoor climate and play a major role in controlling the indoor thermal conditions [15]. Studies on passive environment control methods of achieving thermal comfort in buildings and studies for extracting methods and techniques from traditional buildings are in progress in various countries [16–24]. Researches on the aspect of thermal comfort and energy efficiency of buildings are also underway throughout the world [25]. Although, about 48% of the energy consumed in Indian residential buildings is used for providing thermal comfort indoors [26], studies on environment control aspects of traditional architecture have been reported only recently [27–40]. Kerala, located in the southwest coast of India, has a characteristic Warm-Humid climate because of its geographic settings [41]. 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 sweating. Prolonged exposure to such thermal discomfort conditions can create adverse effects including extensive loss of efficiency in work along with physical strain [42–44]. The authors have conducted an investigation on the passive environment control system of traditional architecture of Kerala. A qualitative analysis discussing in detail about the passive concepts adopted in traditional buildings, a quantitative investigation carried out during all seasons to evaluate thermal comfort and a study based on questionnaire survey among the occupants of traditional and modern buildings on the subjective responses of thermal com-

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Fig. 1. Plan and section of Puthiya Kovilakam located at Nilambur – selected area is marked in rectangle [36].

fort have been reported [32–40]. However, it is essential to have a comparative study of traditional building vis-à-vis modern building to verify the effectiveness of such a passive control system. A field study was thus conducted simultaneously in a selected traditional and a modern residential building during the most unpleasant summer period. This paper presents the passive environment control system of Kerala traditional architecture by analyzing various thermal comfort parameters in comparison with that of modern building. 2. Experimental investigation 2.1. Building description 2.1.1. Traditional building Since the design of Kerala traditional residential buildings is based on a modular concept with four blocks built around an open courtyard strictly adhering to the ancient rules pertaining to geometrical grids, proportions and scale, the investigation is confined to a typical traditional residential building in a selected location. The traditional residential building selected for the study is located at Nilambur in the Malappuram district of the northern part of Kerala. The building (Puthiya Kovilakam) is nearly 300 years old. It has three rectangular courtyards in which one courtyard is surrounded by a double storeyed structure while the other two courtyards are surrounded by single storeyed structures. The internal space taken for the investigation is around the courtyard of 1.83 m × 3.66 m surrounded by double storeyed structures. The courtyard has an inward looking verandah of 1 m width. Two sides of the courtyard are semi open spaces that are used for living. The other two sides are provided with rooms having windows and

doors opening to the courtyard. The average room height of the building is 2.1 m. Plan with selected area for the study marked and a section of Puthiya Kovilakam located at Nilambur is shown in Fig. 1 [36]. 2.1.2. Modern building In order to have a logical comparative analysis, the modern building was also selected from the locality of the traditional building. The residential building selected for the study is located at the south-west side of Puthiya Kovilakam at a distance of 50 m. The 26 years old building “Shinnu” has two bedrooms with other activity spaces arranged as shown in Fig. 2. This building has more or less the most common layout that is generally seen in modern houses. This single storeyed building is constructed with the modern materials i.e., 20 cm thick walls of brick masonry plastered with cement mortar and roof of reinforced cement concrete (RCC). The roof has a slope of 10◦ towards the north and south side for easy drainage of the rain water. The average room height of the building is 3.2 m. A bedroom of size 4.2 m × 3.6 m located at its North-West side (marked in Fig. 2) is selected for the investigation. The bedroom has two windows of size 1.7 m × 1.5 m each, one on the northern side and other on the western side as shown in the figure. The windows are provided with shades projecting 60 cm from the wall for protection from sun and rain. 2.2. Experimental setup The authors have devised an instrument setup called Architectural Evaluation System (AES) with electronic sensors (to record air temperature, mean radiant temperature, relative humidity and air movement), data logger, memory module (to record data from

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Fig. 2. Plan and section of the modern house taken for investigation.

all sensors) and a computer interface (to view and download data to the computer) to continuously record the comfort parameters over a period of time. The threshold speed of air movement sensor is 0.39 m/s and is capable of sensing the required indoor air flow suitable for the investigation. A schematic representation of Architectural Evaluation System (AES) is shown in Fig. 3. 2.3. Field measurements Continuous data for a period from mid February 2010 to mid May 2010 were recorded simultaneously in both traditional and modern buildings. The investigation was carried out keeping the windows open for allowing natural indoor air movement throughout the whole period. This is because natural air flow is an important parameter in determining indoor thermal comfort in a passive system especially in warm-humid climate. Air temperature, mean radiant temperature (MRT), relative humidity (RH) and air movement were recorded using AES that was set to 15 minutes recording interval. The installation of AES done in the traditional and modern building is described below. In the traditional residential building (Puthiya Kovilakam), the temperature sensors were fixed at the bottom and top of courtyard, in the semi open space around the courtyard and in a bedroom adja-

cent to the courtyard. MRT sensors were fixed in the bedroom and semi open space. Sensors were located inside the building to record the air movement in the semi open space around the courtyard. RH sensors were kept in the courtyard, in the semi open space and in the bedroom. Simultaneous recording of outside ambient temperature, RH and air movement were done using sensors suitably located around the building. A photograph showing the installation of AES in and around the courtyard of Puthiya Kovilakam is given in Fig. 3. In the modern residential building (Shinnu), the AES sensors for air temperature, MRT, RH and air movement were positioned in the selected bedroom as shown in Fig. 3. Outdoor ambient temperature and wind speed were also recorded simultaneously. The selected area of the modern house was kept fully in passive mode (no active systems like A/C, fans, coolers, etc. were operated) during the period of investigation. 3. Results The results obtained from the traditional and modern building during the period of investigation, the interpretation of the results, the comparative analysis of the results and the discussion on them are described in the following sections.

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Fig. 3. Arrangement of AES in the modern and traditional residential buildings.

3.1. Results from traditional building It is observed that the outdoor temperature has a diurnal variation of 13 ◦ C i.e., from 28 ◦ C to 41 ◦ C in the region during summer. The indoor temperature was varying from 31 ◦ C to 35 ◦ C showing a diurnal variation of 4 ◦ C only (Fig. 4). The lower part of the court yard was found to be cooler by about 8 ◦ C from the maximum outdoor temperature during the day, while the upper part of the courtyard has a temperature 3 ◦ C lower than the maximum outdoor temperature. The minimum temperature of the upper part of the courtyard was found to be almost the same as that of the bedroom temperature. The maximum temperature recorded inside the bedroom was Courtyard Top

Temperature in Degree C

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found to be lower than that of semi open space around the courtyard. There was no time lag observed between outdoor and indoor temperature and the decrement factor (ratio of diurnal variations in indoor temperature to that of outdoor temperature) is 0.30. The variation of air temperature and MRT, recorded in the semi open space and the bedroom is shown in Fig. 5. While the maximum air temperature of semi open space was slightly more (about 1 ◦ C) than that of bedroom, the minimum temperature is in synchronization with that of the bedroom. While the maximum MRT of the bedroom was about 2 ◦ C lower than the maximum air temperature, the maximum MRT of the semi open space was about 4.5 ◦ C lower than the air temperature. The minimum air temperCourtyard Bottom

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from this figure that the indoor air flow is continuous and maintained around 0.5 m/s and is not totally dependent on the outdoor wind. This is due to the effect of internal courtyard which also allows a continuous and controlled air flow through the building.

atures and the minimum MRTs of the corresponding spaces also have the same trend in variation but with a lesser margin as evidenced from Fig. 5. It was clear from this figure that the semi open space has much low MRT compared to that of the bedroom even when the air temperature of the semi open space is higher than that of the bedroom. The variation of RH of outdoor, courtyard, semi open space and bedroom and the corresponding air temperature of outdoor and bedroom of the traditional house is shown in Fig. 6. It is clear that the RH is inversely proportional to the air temperature. While the outdoor RH was varying from 32% to 95%, the bedroom RH was varying from 50% to 80%. And, while the courtyard was having more fluctuation in RH, the bedroom was having the least fluctuation. It is evident from Figs. 4 and 6 that the variation of RH is well related to the variation of temperature of the respective spaces. Fig. 7 shows the variation of indoor air movement with respect to the fluctuating outdoor wind speed in the traditional building for a continuous period of 19 days in summer. It is evident

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A diurnal variation of 12.5 ◦ C (28–40.5 ◦ C) was observed outdoors when the bedroom temperature was varying from 31 ◦ C to 37 ◦ C showing a variation of 6 ◦ C (Fig. 8). While the maximum air temperature of the bedroom was 37 ◦ C, the corresponding MRT was 38 ◦ C. And, while the minimum air temperature of the bedroom was 31 ◦ C, the corresponding MRT was 31.5 ◦ C. It is clear from Fig. 8 that all MRT readings are higher than the corresponding air temperature readings except for some hours during the day. During that period (9 am to 12 noon), the MRT was matching with the air temperature, as evidenced from the figure. A time lag of about 3 h was observed

Bedroom Temperature Courtyard RH

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3.2. Results from modern building

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between outdoor and indoor air temperature and the decrement factor is 0.48. Fig. 9 shows the variation of indoor air movement with respect to the fluctuating outdoor wind speed in the modern house for a continuous period of 19 days in the peak summer. It is evident from this figure that the indoor air movement is not at all continuous and is fluctuating between 0 and 1.5 m/s and is totally dependent on the outdoor wind.

higher in the modern bedroom and the increase in MRT is from 1.5 ◦ C to 5.5 ◦ C (Fig. 10). The diurnal variations of outdoor and bedroom air temperature corresponding to traditional and modern houses are shown in Fig. 11. From this figure, it is clear that in traditional building, the rate of increase of indoor diurnal variation is less compared to that of outdoor diurnal variation. It can also be observed that the indoor diurnal variation is approaching a steady state when the outdoor variation reaches beyond a limit. On the other hand, in the modern bedroom, the rate of increase of indoor diurnal variation with respect to that of outdoor is very high and it shows an increasing trend (Fig. 11). These distinct trends in the indoor diurnal variation of both the buildings reveal the difference in their passive envir...