Design Guidelines for Climatic Zones in India

Ar. Amitava SarkarDepartment of ArchitectureNational Institute of TechnologyHamirpur 177005.

Design Guidelines forClimatic Zones in India1CONTENTS:

Geographic DiversityTraditional vs. Modern ArchitectureClimatic Zones of the WorldClimatic Zones in IndiaDesign Guidelines for different Climatic Regions

2Geographic Diversity:

Different parts of the world have vastly varying climates, broadly defined by their latitudes. It is important to remember that within the same climatic region there can be significant climatic variations caused by local conditions. A survey of early civilizations indicates a strong relationship between hospitable climates and centres of settled population. At the same time people also settled in extremely adverse or extreme climatic conditions, and they could adapt to the conditions with reasonable comfort. The idealized notion of "comfort" was non existent at that time and it was evident that "adaptability" was possible by mechanism of the human body.

3Traditional vs. Modern Architecture:

We should recognize that vernacular architecture all over the world, especially in the warmer climates, had evolved ways of building to achieve acceptable levels of comfort. These ways of building meant that the building configuration and its fabric would largely attenuate adverse climatic conditions in favour of thermal comfort. If additional devices were required to enhance comfort there would be of a supplementary nature. This strategy when compared to the modern building practice would be inherently more energy conserving.

4Traditional vs. Modern Architecture:

When we compare any contemporary building with a traditional or a vernacular building, we cannot ignore the difference in time and cultural context. Firstly, the standards of comfort people seek today are much higher. In fact, an empirical analysis of the modern day needs of comfort standards would reveal that there is an increasing dependence on high energy systems to maintain ideal indoor conditions irrespective of the varying natural conditions outside.In the wealthy parts of the world it is now taken for granted that buildings will be installed with air-conditioning and heating systems.

5In the poorer parts of the world too with increasing urbanization and gradually rising standards of living there is a sharp rise in the demand for air conditioning and heating. Also, unlike most traditional buildings, the functions that contemporary buildings serve are specialized and demand multiple levels of sophistication in terms of building services and control over the indoor environment. For facilities such as hospitals, laboratories and pharmaceutical production plants there are likely to be very precise requirements for control of air borne dust, temperature and humidity. Luxury hotels, department stores and cinemas would each have their peculiar needs for a controlled indoor environment.

6These two factors led to the heating and air-conditioning industry adopting standards for defining comfort. These standards which were worked out by the American and European industry institutions for their home markets were adopted practically across the globe along with the spread of heating and air-conditioning technologies. These systems are generally based on the use of electricity and fossil fuels as sources of energy. It is estimated that today about 30 percent of all energy consumption is attributable to buildings and their operation. Heating and air- conditioning systems account for about 60- 70 percent of energy consumed in the operation of the buildings where they are installed.

7Climatic Zones of the World:

In order to classify Climatic Zones, climate can be considered at a variety of spatial and time scales.

Approx. Characteristic DimensionsHorizontal Scale (km)Vertical Scale (km)Time ScaleGlobal2 * 1033 - 101 - 6 monthsRegional5 * 102 to 1031 - 101 - 6 monthsLocal1 to 1010-11 - 24 hoursMicroclimate10-110-124 hours 8At the geographic world map level, the Zonal classification is based on maximum and minimum temperatures and the temperature range as well as the total and seasonal distribution of precipitation. A simple summary of climatic zones is as follows:

Summary of climate zonesClimate zoneCharacteristicsPolarvery cold and dry all yearTemperatecold winters and mild summersAriddry, hot all yearTropicalhot and wet all yearMediterraneanmild winters, dry hot summersMountains (Tundra)very cold all year9

Koppen Climate Classification Map

10Within the same climatic zone, some locations may have contrasting or variable climatic conditions. These may be caused by the following factors:

Latitude :Temperature range increases with distance from the equator. Also, temperatures decrease as you move away from the equator. This is because the suns rays are dispersed over a larger area of land as you move away from the equator. This is due to the curved surface of the earth. In addition Polar Regions are colder because the suns rays have further to travel compared to place on the equator. Altitude Temperatures decrease with height. The air is less dense and cannot hold heat as easily.

Winds:If winds are warm - they have been blown from a hot area - they will raise temperatures. If winds have been blown from cold areas they will lower temperatures.

11Distance from the sea:Land heats and cools faster than the sea. Therefore coastal areas have a lower temperature range than those areas inland. On the coast winters are mild and summers are cool. In inland areas temperatures are high in the summer and cold in the winter.

Aspect:Slopes facing the sun are warmer than those that are not. Thus south facing slopes in the northern hemisphere are usually warm whereas slopes facing north in the southern hemisphere are warmest.

12Climatic Zones in India:

India possesses a large variety of climates ranging from extremely hot desert regions to high altitude locations with severely cold conditions similar to northern Europe. Within India it is possible to define six regions with distinct climates.The six climates are normally designated as Hot and Dry, Warm and Humid, Moderate, Cold and Sunny, Cold and Cloudy and Composite.The criteria of allocating any location in India to one of the first five climate zones are that the defined conditions prevail for more than six months. In cases where none of these categories can be identified for six months or longer, the climatic zone is called Composite. On this basis, Bansal and Minke, 1988, originally produced the Climatic Zones in India Map by evaluation of the mean monthly data from 233 weather stations, and then delineating the six climatic zones.

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Climate Zone Map of India

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Climate Zone Map of India

DESIGN GUIDELINES FOR DIFFERENT CLIMATIC REGIONS:

WARM-HUMID Climatic Region:

Key Features:

High humidity, strong sun, glare from the sky and horizon characterize this climate. There are long monsoon periods with heavy rain. But the breezes, especially in coastal areas, can alleviate discomfort considerably.

Mean Monthly Temp. (C) Mean Monthly R.H. (%) Mean Monthly Precipitation No. of clear days in a month Places Warm & humid >30 >5 Trivandrum, Coastal Areas/ North East. 20Key design responses:

Use lightweight construction where diurnal (day/night) temperature range is low and include thermal mass where diurnal range is significant.Maximise external wall areas (plans ideally one room deep) to encourage movement of breezes through the building (cross ventilation).Site for exposure to breezes. Shade whole building where possible in summer.Allow passive solar access in winter months only. Shade all east & west walls & glass year round. Avoid auxiliary heating as it is unnecessary with good design.

21Key design responses:Use reflective and bulk insulation (especially if the house is air-conditioned) and vapour barriers.Use Elevated construction with enclosed floor space, where exposed to breezes.Choose light coloured roof and wall materials.Provide screened and shaded outdoor living.

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23Example:Padamanabhapuram Palace, Trivandrum, Warm and Humid

The Padmanabhapuram Palace in Trivandrum, responds to the climate with steep sloping high tiled roofs, with deep eaves. The sides are open to the breeze, and air ventilates up through the porous tile roofs, ensuring that the indoor temperature does not build up. Using open slatted or perforated timber screens on sides of verandahs cuts out glare, ensures privacy but allows the breeze flow across the rooms. Walls are white to reflect the sun, and often completely shaded by the verandahs. For a cluster of buildings, an openness of planning, to allow the natural breeze to flow through them is of paramount importance.

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HOT & DRY Climatic Region:

Key Features:

Very high daytime temperatures, with very little precipitation and a short and mild winter season characterize this climate. Another important characteristic is a high diurnal temperature variation. One can be boiling during the day and cold at night. This is due to the rapid radiative heat loss from the ground or the building to the clear night sky.

Mean Monthly Temp. (C) Mean Monthly R.H. (%) Mean Monthly Preciptation No. of Clear Days in a month Places Hot & dry >30