Thermal performance of rural architecture in jharkhand case study of typical mud house
Thermal Performance of Rural Architecture in Jharkhand: case-study of typical mud house AR.JANMEJOY GUPTA & DR. MANJARI CHAKRABORTY, BIT, MESRA, RANCHI
INTRODUCTION• Jharkhand as per 2011 census, has 75.9 % of its total population living in rural areas.• 30% of the world’s total population live in earthen structures.• Earthen huts constituted 48% of total residential construction until 1960 in Jharkhand.(Das & Pushplata, 2005).• An 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.• Huts were arranged in a linear pattern along the main street of a village, usually amidst a group of bamboo trees. The houses were 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.
PHOTOGRAPHS OF RURAL HUTS Source: photos by the Author
CONSTRUCTION TECHNIQUES• 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 was 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 mud’s plasticity (Cooper & Dawson, 1998).• 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.
…continued• The walls were formed by applying a thick coat of the mixture on both sides of bamboo/sal log mesh that wrapped around the posts. 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 (Dhar, 1992).• These posts were sunk into the raised platform and tied with wooden beams and purlins that supported the roof structure. The huts usually had a gabled thatch roof. Bamboo sticks formed the mullions to support the thatch.• thatch in the huts was replaced later by sun-dried or burnt clay Mangalore tiles.
The four types of mud-house construction employed are: • 1. Cob: Fresh lumps of mud [soil & water & local fibre materials] stacked on each other. Stacking lumps of mud. • 2. Wattle and Daub: Woven work of sticks intertwined with twigs or bamboo covered with mud . • 3. Rammed Earth: Damp earth laid between formwork and moulded and compacted by ramming. • 4. Straw-bale: 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.
Mud house construction-techniques & types..continued:Source:Uthaipattrakul, Dh. (2004). Mud-house construction technique.Building the house with mud. Suan-ngarn-mena Press, Bangkok, 27-50. Special mud blocks left with vegetable waste matter to mature for wall construction. Mud wall with wooden-posts of typical hutSource: Gautam Avinash(2008), Climate ResponsiveVernacular Architecture: Jharkhand, India, Masters OfScience Thesis, Department of Architecture, Kansas StateUniversity, Manhattan,Kansas. Source: Dhar (1992)
CLIMATE OF RANCHI • As per Koppen’s classification, Ranchi has sub-tropical humid climate. • A humid subtropical climate as per Köppen climate classification is a climate zone characterized by hot, sometimes little humid, summers and generally mild to cool winters. • Summer is followed by the cooler monsoons, where the region experiences heavy rains on almost every alternate day basis. Average high temperatures decreases during the monsoon season but the humidity increases. • Summers tend to be hot, starting from mid-April and peaking in May and early June with high temperatures often touching 40°C. They also tend to be dry, complete with dust storms, traits usually associated with arid or semiarid climates.
METHODOLOGY-STUDY HUT • The hut is located in Mesra village, 16 kms from Ranchi. Its dimension is 12 meters in length by 7 meters in breadth. 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 method. • The two doors are placed in the southern side. The solitary small void like opening is placed on the northern wall.
1.PARAMETERS OF STUDY, FIRST PARAMETER • Orientation: The mud house has its longer side oriented along East-West Axis. The two doors are placed in the southern side. The solitary small void like opening is placed on the northern wall.Ecotect software analysis of simulated study-hut – Mean radiant temperature (Thermal Comfort) inside mud hut at 12Noon, 1st June. East-West Orientation of house, void (window like smaller opening) on northern wall.
ANALYSIS - Orientation• 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. Ideal Orientation for heat & ventilation
Ecotect software analysis of simulated study-hut – Mean radiant temperature (Thermal Comfort) insidemud hut at 12 Noon, 1st June longer side orientated along NW-SE direction, at an angle of 45 degrees tothe East-West Axis. Void on northern wall.
Window on southern face, results in higher average temperature. Not advisable.
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 & also 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 annual heating and cooling energy saving potential of a vault roof mud- house was determined as 1481 kW h/year and 1813 kW h/year respectively for New Delhi composite climate. The total mitigation of CO2 emissions 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 & also encourage convective cooling at night. Source: Arvind Chel,G.N.Tiwari(2009), Case study of vault roof mud-house in India, Thermal performance and embodied energy analysis of a passive house , Energy, Volume 86, Issue 10, October. (An original research article) Pages 1956-1969.
Surface Area to Volume Ratio(S/V)Improved thermal comfort in vaulted roof building made of stabilized mud blocks (composition: soil, sand,lime/cement and water) (east west orientation)SEMI-HEMISPHERICAL SPACE IN BETWEEN VAULT ROOF CAN ACT AS A THERMALBUFFER. ALSO OPENINGS IN VAULTED ROOF CAN ALLOW FOR CONVECTIVE COOLINGAT NIGHT BY ALLOWINGS WARM AIR TO ESCAPE & ALLOW COOL AIR FROM OUTSIDECOOLED SURROUNDINGS TO ENTER.
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 Ideal nocturnal ventilative cooling carried out and increase the overhangs. with small gap to allow air-flow.
The above graph generated through Ecotect software for the period from 1st January to30th June shows, heat gain and heat loss sources. Whereas heat loss is showed throughbe mainly through conduction (95.5%), the heat gain is showed to be through acombination of ventilation/air movement (69.9%) and conduction (28.4%),validating the need for convective ventilative cooling at nighttime in summer for loss ofheat gained during the day.
passive heat gains breakdown in studied hut(10th May-10th June)
model hut-different temperature gains - sources
4. Building Materials• The building material for the walls is mud (U Value 3.44 W/sq m K) and the roof material is Mangalore Tiles. The U value for thatch is 0.35 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 can be mitigated with modern day industrially improved hatch use.
Thatch…• 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 (30 cm) 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 (10 cm) 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.
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. Shading is needed at daytime, in summer. (specially from 10 AM- 3:30 PM)• Analysis: If shading is increased by having greater eave projections and also sunken window or chajjah then heat gained can be considerably reduced. Thermal Comfort at 9 P.M, 1st June at night (Ecotect simulation)
Thermal Comfort at 12 Noon, 1st September (Ecotectsimulation)
RESULTS OF OCCUPANT-SURVEY-MERITS & DEMERITS• The occupants of the hut moved outdoors during the evenings in summers because of air movement; air movement inside the house was very less. 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 peak summer and peak winter. They also felt humidity and lack of air movement were uncomfortable in summer & sometimes in monsoon.• Occupants of some huts said that the rainy season was the most uncomfortable season.• Temperature measurements results indicate that the selected hut exhibited lower ambient temperature than outside during the day and a marginally higher ambient temperature at night.
More Changes that can be made in existing hut-earth berming
OBSERVATIONS• 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 /domical roof mud-house and having proper openings in roof which guard against water ingress of huts to facilitate nocturnal ventilative cooling, etc.• Modern day industrially improved thatch can be used with all the good thermal properties intact and the disadvantages of thatch gone.• More research and study is needed as to how to increase build-ability and durability of mud houses along with doing away with certain negative aspects commonly found in mud houses like high humidity during monsoons, fungal growth & vegetation growth in mud and negative properties of hatch to be mitigated.• Temperature measurements results indicate that the selected hut exhibited lower ambient temperature than outside during the day and a marginally higher ambient temperature at night. This needs to be corrected.
OBSERVATIONS..continued• 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.
REFERENCES• 1. Krishan Arvind, Baker Nick, Yannas Simos, Szokolay S.V. (2001), Climate Responsive Architecture – A Design Handbook for Energy Efficient Buildings, Tata McGraw-Hill Publishing Company Limited, New Delhi.• 2. Olgyay Victor (1963), Design With Climate- Bioclimatic Approach to Architectural Regionalism, Van Nostrand Reinhold, New York.• 3. Majumdar Mili.(2001), Energy-Efficient Buildings In India, Tata Energy Research Institute, Ministry of Non-Conventional Energy Sources.• 4. Arvind Chel,G.N.Tiwari(2009), Case study of vault roof mud-house in India, Thermal performance and embodied energy analysis of a passive house , Energy, Volume 86, Issue 10, October. (An original research article) Pages 1956- 1969.• 5. Garg H.P, Sawhney R.L (1989), A case study of passive houses built for three climatic conditions of India, Solar & Wind Technology, Volume 6, Issue 4.• 6. Gautam Avinash(2008), Climate Responsive Vernacular Architecture: Jharkhand, India, Masters Of Science Thesis, Department of Architecture, Kansas State University, Manhattan,Kansas.• 7. Uthaipattrakul, Dh. (2004). Mud-house construction technique. Building the house with mud. Suan-ngarn-mena Press, Bangkok, 27-50.