Indigenous architecture of two Indian deserts and modern climatic responsive solutions

Indigenous architecture of two Indian deserts and modern climatic responsive solutions

WREC 1996 Indigenous Architecture of Two Indian Deserts and Modern Climatic Responsive Solutions Prof. Dr. Arvind Krishan Professor& Chief Coordinato...

1MB Sizes 0 Downloads 17 Views

WREC 1996

Indigenous Architecture of Two Indian Deserts and Modern Climatic Responsive Solutions Prof. Dr. Arvind Krishan Professor& Chief Coordinator

Kunal Jain, Pashim Tewari ResearchAssociates Center for AdvancedStudiesin Architecture School of Planning& Architecture,New Delhi, India

0.0 Abstract: This paper presents the climate responsive principles of architectural design evolved through time in the development of indigenous architecture. A scientific analysis of settlements at Leh (Ladakh) and Jaisalmer (Rajasthan) presents their appropriateness in terms of thermal performance. Principles of architectural design evolved in these settlements when applied to modem buildings, illustrated through two projects designed by the author, suggest how low energy architecture, that is, sustainable, can be developed in the modem context, basically by way of architectural design.

1.0 Preamble: Indigenous architecture of India, creation of a 'Process of Triai and Error' is in essence a product of evolution. A product that has developed in response to climate (laws of nature) and the needs of the people within their socio-economic context. Since climate is an intrinsic paradigm of design in the process of indigenous architecture, the product of this process is low energy consuming making it non-consumptive of natural resources. A scientific evaluation of indigenous architecture at Leh (Ladakh - Cold Dry climate) and Jaisalmer (Rajasthan - Hot dry climate) reveals that these built forms are very fine examples of site planning, architecture and provide models which on analysis help generate methodology and criteria for planning and design of new settlements and buildings in these climate zones.

INDIGENOUS ARCHITECTURE A CLIMATE RESPONSIVE DESIGN 2.0 Leh (Ladakh). a high altitude 'cold-dry' mountainous desert: The habitat of Leh located at a height of 3514 meters above sea level has a climate characterized by a very large range of variation in ambient temperatures annually. Summer temperatures vary from 24.7°C (mean maximum) to 8°C (mean minimum) with a diurnal range of 15°C. Winter temperatures vary from -2.8°C (mean maximum) to -14°C (mean minimum) with a diurnal range of 16°C. Although a maximum of 37°C in summers and a minimum of-30°C has also been recorded. Sky tends to be clear for a large part of the year, therefore direct radiation levels in the area are very high with low levels of annual precipitation < 115 mm. Winter is the critical season prevalent for the most part of the year, sununer is very mild. Fig 2.1 Settlement pattem of Spituk

272

~ '

WREC 1996 2.1 Settlement Pattern - Spituk (Leh): Solar Access a primary element of design Winter is the critical season, heating by natural means is the major requirement of the region, sun is the only source for natural heating. Settlement pattern is the first level of control against the harsh cold climate. Entire settlement is located on the south face of the hillock, with an open settlement pattern maximizing heat gain from solar exposure, it eliminates cold winds effectively from the North-East side by this careful choice of the site (fig 2.1). 2.2 Generic House: The Generic House in Spituk and indeed in the region of Ladakh is a compact two to three storey house in Sun dried mud blocks. The walls are very thick, tapering in thickness from ground floor to the top with average thickness of almost 1.0 M. The doors and window fenestration are small. Houses provide for a hierarchy of spaces both enclosed and unenclosed where a good solar exposure is available. The buildings typically don't have any overhang thus preventing any shading of the surfaces. Basic design of the house is to maximize solar penetration and thereby heating by natural means. 2.3 Thermal Performance of buildings in Spituk: • Thermal performance of the typical Ladakhi house is very good. Whereas the ambient conditions fluctuate between a minimum low of-20°C to a maximum of-5°C in winters and minimum low of 3°C to maximum of 14.7°C in summers, the internal temperatures stay very stable and at best fluctuate between 12°C to 15°C. Thick mud walls provide a large thermal mass leading to a large time lag and small decrement factor, thereby effectively attenuating the external ambient conditions. • Small windows and small doors- typical to old Ladakhi houses since glass was not available - minimize heat loss and eliminate ingress of cold wind. • Windows are typically splayed in the thick mud walls to provide minimal area of exposure on the outside and a larger area on the inside face. This allows a greater distribution of daylight inside. 2.4 Climate responsive elements of design: Spatial hierarchy, siting of buildings, exposures of buildings(orientation) are the basic elements of design, making it a very f'me example in site planning for maximizing solar exposure. Careful control has been exercised on the plan form of buildings, street width to building height ratio, building to building relationship in order to maximize solar penetration. Analysis of these elements provides the planning and design parameters for this climatic context. A Heliodon study of model of the site reveals the level of solar penetration.

Fig 2.4

Shadow penetration study for Spituk at 12 noon and at mid-afternoon.

273

W R E C 1996

3.0 Jaisalmer (Rajasthan) - Hot Dry Jaisalmer situated at 26055 ' North Latitude and 75055 , East longitude at 241.7 M above mean sea level was founded by Maharwal Jaisal Singh in 1156 AD It was founded as a fort city on a hilly out-crop of the Arawali range called "Trikut" because of its triangular shape. Surrounding landscape is flat, rocky and barren, the region is characterized by sparse vegetation and acute scarcity of water. Water is a valuable resource in the area. In times of draughts water is not available for kilometers at a stretch. This site was selected since it has the availability of sub-surface water. There is very little and unreliable rainfall (average annual precipitation <200 mm). Two seasons are predominant, summer and winter. In summer, day time temperature can reach up to 45°C (some peak conditions of 50°C have also been recorded) and down to 25°C at night. Similarly in winter, the temperatures vary between 25°C and 5°C. The diurnal range of temperature is between 15°C to 20°C. Relative humidity in summer Can be less than 10% in the day time. Sky is mostly clear and solar radiation is intense through out the year. During summer months the wind velocity is usually high and there are dust storms during May and June.

3.1 Settlement Pattern: The entire fort city of Jaisalmer is built on a height generally following a triangular geometry (Fig.3.1). City is characterized by a triangular fortification and by narrow winding streets with densely built construction on both sides. It has reasonably large open spaces to serve as community spaces. The house planning and design is characterized by a court-yard with an underground level. The house o p e n s on to n a r r o w streets through hierarchy of spaces that become the interface between the street and the house. The entire city ranging from the small houses to the Palace of the king is built in locally available light yellow Jaisalmer stone which is basically a sand stone.

~A~

~

Fig 3.1

The settlement pattern of Jaisalmer.

3.2 Street Layout: All major streets are oriented almost in the East-West direction at right angles to the direction of dust storms (Fig.3.1). The famous havelies with jharokas and decorative facades are located on these streets. The streets are relatively narrow and winding. The height of the building compared to the width of the streets is large to create shaded cool environment for the pedestrians and other social activities on the streets.

3.3 Generic House: The generic house type in Jaisalmer is court-yard type, with unenclosed verandah around the courtyard, an enclosed room and an underground space used for storage and living. Variations of the courtyard house occur in the form of a simple single storey house an elaborate havelies.

274

W R E C 1996

3.4 Thermal Performance of buildings: •

Thermal performance of haveli type buildings is very good. Ground floor temperatures don't fluctuate more than 3°C while outdoor temperatures fluctuations are 15°C. Maximum indoor temperatures are 8-9°C lower than the corresponding outdoor temperatures.

* Court-yards ensure ventilation through buildings even in calm outdoor conditions. •

Combined effect of greater time lag and small decrement factor reduces heat flux entering the building.

Fig 3.3

Section through a typical haveli

Due to mutual shading, jharokas and rich textured surfaces (because of carving), the impact of direct solar radiation is minimized. In summers this minimizes the heat flux entering the building. In winters, lower altitude of Sun allows reasonable penetration.

3.5 Climate responsive elements of design: • Built form and micro climate: Built form and micro climate are interactive. Buildings influence micro climate around them as much as the micro climate influences the buildings. Temperatures in different areas recorded corresponding to the ambient conditions, indicate, street temperatures are lower than the ambient in the day time and the night in summer by 2.5°C to 3°C, whereas in winter it was higher by 2°C. These street level temperature variations indicate the effect of built form

Dense compact settlement: In Jaisalmer layout of the settlement is the first level of control against climate. Compact settlement generates a large thermal mass attenuating the external ambient conditions. Street orientation ensures that building facades are either shaded byjharokas (balcony) or chajjas (sun shade) projections or by the buildings opposite.

Solar penetration control by orientation and projections: In summer the major East-West street orientation should have solar exposure on the street from 9.30 AM to 2.30 PM with corresponding solar altitude varying from 54 ° to 86 °, therefore small projections can help shade the surface completely. The north face of the building on the opposite side of the street will receive radiation before 8 AM and after 4 PM with solar altitude less than 35 ° . Therefore building on the opposite streets provide the shade on the north face.

10 A.M, 9 A,M,12 A.M. 8 A.M. 11 A.M. 7 A.M 6A..

1 P.M.

For minor streets along north-south orientation, solar exposure is on the east face in summers till 11.30 AM and on the west face after 12.30PM. Solar altitude during this period is 0° to 79 °, when the narrow streets within the buildings get shade before 10.30 AM and after 1.30 PM, therefore solar radiation incident on East and West facades is for no more than one hour.

Control of heating by texture on surfaces: Heat flux entering the building is controlled by the use of textures in Jalsalmer, organized at three levels. At the habitat scale the buildings are of unequal height with parapets and high walls, creating sky lines and desired shading of each other, Secondly,

Fig3.5 Solar penetration on June 21st at different times of the day.

275

WREC 1996 building facades have a large number of projections likejharokas and chajjas which provide shade on facades. Thirdly, the front facades which remain exposed are controlled by creating deeply carved patterns. This device minimizes the heat gain in day time by providing shading due to textured surface, they reduce heat gain by increased convective heat loss due to increased surface area. In the evening when ambient conditions are cool the increased surface area helps in cooling faster. Thick stone wall, timber & mud floors construction: Due to typical thermal lag available because of thick construction which also has a large thermal capacity, outside conditions are attenuated to provide comfort conditions inside. Ventilation - court yard: In the hot conditions prevailing in Jaisalmer and due to scarce availability of water the only effective means to achieve sensible comfort is by increasing ventilation through spaces by drawing air from cooler areas. In Jaisalmer the combined effect of court yard and internal vertical shafts is used for creating ventilation. Coupled with high thermal inertia of massive construction these shafts temper the air before it enters a living space.

MODERN BUILDINGS DESIGN

-

PRINCIPLES OF INDIGENOUS ARCHITECTURE TRANSLATED

Principles of architectural design elicited from a scientific study of indigenous architecture have been applied by the author in the design of many projects. Two projects in the climatic context of regions described above are presented as examples of achieving climatic responsive and sustainable architecture by way of architectural design and not by tacking on devices. 4.0 'Degree College' Complex at Leh: An institutional building complex (fig. 4.0) with academic and residential facilities for students working towards their first graduation degrees. This is a project located in the harsh cold-dry climate context of Leh described above for 'Spituk'.

...-N

\

/ ~="~" '° ~°~'~'

\

\

\

\

\

\

\

\

\

\

\

\

\

x

\

\

t

\

\

\

\

Fig 4.0 Siteplan of Degree College, Leh

4.1 Elements of design: Climate is predominantly cold, requiting heating for almost the entire year. A short period in summer is comfortable in the day time. Since sky tends to be clear for most of the year direct radiation levels are very high. This design exploits the availability of heat from high solar radiation by maximizing solar penetration into the building. Major features of this design may be Fig 4.1 Section through summed up as follows: Lecture Theatres. 276

R

WREC 1996 • The Design allows maximum exposure of all buildings to the sun through its daily and annual movement. • A l l buiMing elements receive 100% solar radiation during critical movements. • Major use spaces : lecture theatres, laboratories, library etc. are heated by solar energy (abundant in Leh) using direct gain (through split roofs) and indirect gain (through thermo-siphoned air-heating systems built into the south walls). • Light distribution is optimized in all spaces by reflection off light shelves and ceiling, also reducing glare. • All spaces have a solar heated entry space with a double door, serving as an airlock. • All corridors are heated by adequate solar access by placing them away from the cold north or the middle zone. • Embodied energy consumption in building construction is optimized by use of local materials, mainly mud and stone.

5.0

Punjab Energy Development Agency Office Complex at Chandigarh

An Office Complex in the "Composite' climatic context i.e. a predominantly hot climate with a hot-dry, hot-humid, temperate and cold periods.

Fig 5.0 SectionalPerspective through the Office Complex.

5.1

Elements ofDesign :

Building requires cooling for the long hotdry and hot-humid periods and heating during the cold winter periods. This has been achieved in the following manner : • A unique floating slab system with an open landscape office pattern within overall envelope of the building. The envelope eliminates heat flux due to radiation and ambient air temperatures in the hot-dry and hot-humid period, but allows solar penetration in the cold-winter period for heating. • A series of vertical cut-outs punctuating the floating slabs at different levels/floors allow quick movement of cool air generated from the large volume of the central area which is cooled by a wind tower. • Controls on the envelope are designed to allow solar access in the winters for Fig 5.1 GroundFloorplan of the PEDA Complex heating the building quickly. Floating slabs at different levels synthesizes with cutouts for even and easy penetration of daylight. 277