SUSTAINABILITY OF RURAL MUD HOUSES IN JHARKHAND: ANALYSIS RELATED TO THERMAL COMFORT

ABSTRACTThis paper aims to assess passive solar design techniques and the extent to which they promote high thermal comfort in a vernacular rural mud house in the state of Jharkhand in India. The study of this mud house provides an insight for designing an energy efficient rural house that provides thermally comfortable conditions, as well as leaving behind a very low environmental footprint. The existing realities of the mud house are studied and a few reforms have been suggested after a thorough study.Jharkhand has, as per the 2011 census, 75.9 % of its total population living in rural areas, and it is in this context that the development of proper rural architecture is important. With the energy crisis deepening, the role of the built environment becomes more significant. Mud has a number of properties which make it a perfectly suitable material for constructions which aim at achieving thermal comfort at a low cost specially in a climate like that of Jharkhand. The various parameters which are considered in the study of the existing mud house are orientation, plan-form, building exposure to sun, surface-volume ratio, openings, shading, building envelope material, roofing materials and ventilation.As a tool for studying the thermal comfort conditions inside the mud house and in order to simulate different thermal conditions, the software Autodesk Ecotect Analysis sustainable design analysis is used. Once the existing realities of the mud house under the existing conditions is studied, the paper intends to suggest reforms and a few passive design strategies through which existing conditions in the hut can be improved. Key Words Mud architecture, Passive Design strategies, Thermal Comfort, Environment Friendliness, Simulation, Thatch,

1.0 INTRODUCTIONSince the Iron Age, Jharkhand has been a land of thirty different tribes on the Chotanagpur plateau. Before British colonization in 1870, Jharkhand had an agrarian society. Huts made of mud walls and thatched roofs were the standard construction. Along with a thermally-responsive construction, the architecture of Jharkhand also responded to interactive social life by creating community courtyards. According to available data, these buildings constituted 48% of total residential construction until 1960 (Das & Pushplata, 2005).Jharkhand has, as per the 2011 census, 75.9 % of its total population living in rural areas, and it is in this context that the development of proper rural architecture is important. With the energy crisis deepening, the role of the built environment becomes more significant.Jharkhand predominantly has two different styles of vernacular houses: huts and havelis. These houses were constructed, without any mechanical means, in such a manner as to create micro-climates inside them to provide high thermal comfort levels. Out of these two, mud houses have a lot of potential to provide both reasonable living conditions and thermal comfort at affordable prices for the rural people if properly dealt with. 30% of the worlds total population lived in earthen structures in 1990 as reported by Cofirman et al. (1990)1.1 Typical Existing Vernacular Mud Huts in Jharkhand in rural and suburban areas1.1.1 Size & LayoutAn average hut measured approximately 5 to 6 meters (15 to 18 feet) long and 3 to 4 meters (10 to 12 feet) wide (Dhar, 1992). The huts vary in size. There are also a considerable number of larger huts that extend up to 12 to 14 meters in length and 8 to 9 meters in width. These huts are arranged in a linear pattern along the main street of a village, usually amidst a group of bamboo trees. The houses are normally surrounded by a fence made of bamboo, shrubs, or twigs that defined the boundary between the public street and the semi-public courtyard area in front and at the rear of the hut. This open-to-sky courtyard acts as a prime space for the house, especially during the day in winter and in the evenings in summer. Most day to day activities occur in this space. Often there is a well in this courtyard that serves as the source for water for drinking, bathing, washing, and cooking. (Figure 1) People use this courtyard to dry clothes, crops, and eatables during the day time. The aged of the house use this as a rest area, supervising the children at play.The houses are often on a raised platform made of compacted earth. The high thermal mass helps to keep the house cool in the evenings in summer which makes it pleasant for people to rest in the evenings. The huts normally have minimal openings. Often the only opening on the external walls is the main door. Some houses have windows, but they are small and placed high to ventilate the indoors while, at the same time, acting as a visual barrier for the private spaces. The small windows also help to keep the hot summer sun and cold winter winds out.

Figure 1: Courtyard Type Planning, often with wells provided in the courtyard (source: photographs by author)

1.1.2 Typical mud huts in Jharkhand construction & detailsThe four types of mud-house construction employed in Jharkhand are:

1. Cob: Fresh lumps of mud [soil & water & local fibre materials] stacked on each other. Made by stacking lumps of mud. (Figure 2)

2. Wattle and Daub: Woven work of sticks intertwined with twigs or bamboo covered with mud. (Figure 3)

3. Rammed Earth: Damp earth laid between formwork and moulded and compacted by ramming.

4. Straw-bale: Made by plastering the bundle of hay with mud. Out of these, the Cob method & Wattle and Daub method is the most commonly used in Jharkhand huts. Wattle and Daub was the method used in the hut studied. Figure 2: Cob Construction Figure 3: Wattle & Daub ConstructionSource: Uthaipattrakul, Dh. (2004). Mud-house construction technique. Building the house with mud. Suan-ngarn-mena Press, Bangkok, 27-50. The hutments were originally built of mud, sticks, grass, and pebbles. These houses were mostly self-built by family members, sometimes aided by neighbours. Traditional architecture developed its individuality by tapping nearby resources and exploiting them to confront problems posed by the local environment (Cooper & Dawson, 1998). The huts were made of local materials. Timber, bamboo, clay, straw, cow dung, and a special variety of grass were used to build houses (Dhar, 1992). The walls were made of a special type of mud obtained by souring earth by adding vegetable waste and leaving it to mature. The decaying waste produced tannic acid and other organic colloids, greatly improving the muds plasticity (Cooper & Dawson, 1998).(Figure 4) This mud was then mixed with cow dung, chopped straw, and gravel or stones to make the raw material for the walls. In the Middle East fibrous ingredients like straw are used to improve tensile strength of mud bricks. Binici et al (2007) investigated the thermal isolation and mechanical properties of fibre reinforced mud bricks as wall materials.

Figure 4: Special mud blocks left with vegetable waste matter to mature for wall construction.

Figure 5: Mud wall with wooden-posts of typical hut plan & detail (Reproduced from Dhar, 1992)

Figure 6: View of decayed thatch roof in a hut over a period of time. (Source: Gautam Avinash(2008), Climate Responsive Vernacular Architecture: Jharkhand, India, Masters Of Science Thesis, Department of Architecture, Kansas State University, Manhattan,Kansas.

The walls were formed by applying a thick coat of the mixture on both sides of bamboo mesh that wrapped around the posts (see figure 5). Sometimes the mesh was made of wooden logs obtained from sal trees that grow in abundance in this region. The walls are approximately 450 mm (18 inches) thick. The roof rested on nine wooden posts erected in three rows, with three posts per row, as shown and purlins that supported the roof structure. The huts usually had a gabled thatch roof. Bamboo sticks formed the mullions to support the thatch. The thick thatch used as roofing material prevented rain from entering the house and at the same time provided insulation to the building. While providing some benefits to the house, thatch had its own drawbacks. It tended to house parasites, rodents, and birds (see Figure 6). Over time, as an effect of industrial hybridization, the thatch in the huts was replaced by sun-dried or burnt clay Mangalore tiles that are today more commonly used as roofing material for the huts as has been done in the house studied. { Gautam Avinash(2008), Climate Responsive Vernacular Architecture: Jharkhand, India, Masters Of Science Thesis, Department of Architecture, Kansas State University, Manhattan,Kansas.}

2.0 STUDY & ANALYSIS OF EXISTING MUD HUT. The hut is located in Mesra village, 16 kms from Ranchi. Its dimension is 12 meters in length by 7 meters in breadth. (Figure 7) It is made of mud walls and has a Mangalore tiled roof. It has 450 mm thick mud walls and was constructed by wattle and daub construction. Ranchi has a Sub-Tropical Humid type of climate as per Koppens Classification of Indian Climates. (Fig 7) Figure 7: Source: www.ijlct.oxfordjournals.org Figure 8: Digital Recreation of Study Hut2.1 Orientation: The mud house has its longer side oriented along East-West Axis. The two doors are placed in the southern side. (Figure 8)The solitary small void like opening is placed on the northern wall.

Figure 9: Study Hut, photographs (source: photographs by author)

Figure 10: Ecotect software analysis of simulated study-hut Mean radiant temperature (Thermal Comfort) inside mud hut at 12 Noon, 1st June. East-West Orientation of house, void (window like smaller opening) on northern wall.Analysis: The best orientation for least heat gain for rectangular built form with one side longer than the other is the longer sides facing the East-South and North-West direction making an angle of about 40 degrees or 45 degrees with the East-West Axis, rather than the longer side of the building aligned along the East-West Axis as done in the mud house studied. With the longer side orientated along NW-SE direction heat gained would be even lesser. Thus, with proper orientation, the heat gained by the mud house would be even lesser. (Figure 11) Figure 11: Ideal orientation of hut for least solar heat gain in summer & ventilation

Figure 12: Ecotect software analysis of simulated study-hut Mean radiant temperature (Thermal Comfort) inside mud hut at 12 Noon, 1st June longer side orientated along NW-SE direction, at an angle of 45 degrees to the East-West Axis. Void on northern wall.

Figure 13: Ecotect software analysis of simulated study-hut Mean radiant temperature (Thermal Comfort) inside mud hut at 9 AM, 1st June longer side orientated along NW-SE direction, at an angle of 45 degrees to the East-West Axis. Void on northern wall.

Figure 14: Window on southern face, results in higher average temperature. Not advisable.2.2 Surface Area to Volume Ratio(S/V): The total surface area (excluding ventilation opening & including roof area) is 185 square meters in mud hut studied. The total volume is 210 meter cube. The ratio comes to be 0.88. In composite or sub-tropical humid type climate the S/V ratio should be as low as possible as this would minimize heat gain.Analysis: The Surface Area to Volume Ratio can be reduced further by using a domical or vaulted roof. A domical roof & vaulted roof would further reduce direct heat gain. A vault roof mud-house with roof made of stabilized mud blocks (composition: soil, sand, lime/cement and water) would be very helpful in creating better thermal comfort. The vault would also induce better convective air movement thereby cooling the internal space.The annual heating and cooling energy saving potential of a vault roof mud-house was determined as 1481 kWh/year and 1813kWh/year respectively for New Delhi composite climate. The total mitigation of CO2emissions due to both heating and cooling energy saving potential was determined as 5.2 metric tons/year. A vaulted roof would also increase the attic area, which can act as a thermal buffer and help in thermal insulation both during summer and winter.

Figure 15: Improved thermal comfort in vaulted roof building made of stabilized mud blocks (composition: soil, sand, lime/cement and water) (east west orientation)2.3 Ventilation: The portion through which cool air at night could come in at the top portion of the roof and through which warm air can go out by convective process has been blocked in this particular hut due to rain water coming inside the hut during rains. This causes lack of ventilation in summer and convective air flow at evening and night. A probable solution is to let the openings remain and cover them by bamboo mesh like surface to stop rain water coming in monsoons. (Figure 16) Figure 16: Extended Eave projection & bamboo meshing to prevent rain ingress & allow ventilation Figure 17: Ideal nocturnal ventilative cooling carried out with small gap to allow air-flow.

Figure 18: Heat Gain/Loss Breakdown (Period- 1st January to 30th June)The above graph generated through Ecotect software for the period from 1st January to 30th June shows, heat gain and heat loss sources. Whereas heat gain is showed through be mainly through conduction (95.5%), the heat loss is showed to be through a combination of ventilation/air movement (69.9%) and 28.4% validating the need for ventilative cooling in summer for loss of heat gained during the day.2.4 Building Materials: The building material for the walls is mud and the roof material is Mangalore Tiles. The U value for mud is 3.44 W/sq m K & the U value for Mangalore Tiles is 3.1 W/sq m K. Analysis: Though U value of Mangalore/Clay Tiles and khapra used is not that high, the insulating property of thatch is much more, as its U value is even lesser. So in summer, it keeps the inside of the hut even cooler than clay tiles do. The disadvantages with thatch as mentioned before in this paper can be mitigated with modern day industrially improved hatch use.Modern day thatch treated and improved industrially can also be used for mass use in rural areas, being low cost and having very good thermal properties. Thatch is a natural reed and grass which, when properly cut, dried, and installed, forms a waterproof roof. The most durable thatching material is water reed which can last up to 60 years. A water reed thatched roof, 12 inches thick at a pitch angle of 45 degrees meets the most modern insulation standards. The U-value of a properly thatched roof is 0.35 W/sq m K, which is equivalent to 4 inches of fibreglass insulation between the joists. Only in the last decade have building codes begun to demand this level of roof insulation. Yet, thatch has been providing insulation since much longer.2.5 Shading: There is no shading except for the projection of the roof. Due to the high solar elevation angle around noon time during the summer period, solar radiation on south-facing facades is lower and direct sunlight is easier to shade.Analysis: If shading is increased by having greater eave projections and also sunken window or chajjah then heat gained can be considerably reduced.

Figure 19: Thermal Comfort at 9 P.M, 1st June at night (Ecotect simulation)

Figure 20: Thermal Comfort at 12 Noon, 1st September (Ecotect simulation)

Figure 21: Passive heat gains breakdown in studied hut(10th May-10th June)

Figure 22: Probable cooling in summer by earth-berming.3.0 RESULTS OF OCCUPANT-SURVEY The occupants of the hut moved outdoors during the evenings in summers because of air movement; air movement inside the house was nearly non-existent. This further necessitates the use of nocturnal ventilative cooling carried out with small gap to allow air-flow through slit like openings in the roof with suitable eve-projections. Despite spending most of their time indoors, washing, bathing, drying of clothes, praying were done in the courtyard early in the morning when the temperature outside was cooler than in the afternoon. The users slept inside the huts throughout the year. Occupants of the entire hut felt more comfortable all day inside the house during summer because it was relatively cooler inside than out. Some occupants said temperature was most uncomfortable in summer and winter. They also felt humidity and lack of air movement were uncomfortable in summer. Occupants of the other huts said that the rainy season was the most uncomfortable season because they could not perform day-to-day activities as usual. Temperature measurements results indicate that the selected hut exhibited lower ambient temperature than outside during the day and a slightly higher ambient temperature at night.

4.0 OUTCOMES The Mud house studied reinforced the fact that mud as a building envelope keeps the inside of the hut cooler in summer. However the cooling effect of these traditional mud houses can be further improved and living conditions inside the huts improved by proper design considerations like proper building orientation, surface-volume ratio minimisation, creating vaulted roof mud-house(roof made of stabilized mud blocks) and having proper openings in roof which guard against water ingress of huts to facilitate nocturnal ventilative cooling, use of shading devices being properly used and proper building material selection which can be economically viable for rural areas as well as have proper thermal insulation properties. Earth-berming can be also used to proper insulating effect.(Figure 22) Modern day industrially improved thatch can be used with all the good thermal properties intact and the disadvantages of thatch gone. Use of rationalized traditional technologies, like that done and displayed at the Rural Building Centre of National Institute of Rural Development, Hyderabad (NIRD), a HUDCO initiative, which has created model huts for 16 diverse climatic areas of India including Kutch regions, hot-dry area, coastal high-rain areas, Deccan Plateau, etc. However the region Jharkhand with its sub-tropical humid climate or composite climate does not feature in the list of those 16 regions. It would be a great boon to the vast rural populace of Jharkhand if they could see their modest mud-house being improved by use of rationalized traditional technologies and if they could be given a easily constructible prototype mud-hut on the lines of the 16 other prototypes being developed by the NIRD initiative. These can be systematically being made available to the rural poor through awareness and government initiatives and loans/grants.

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