Different parts of India experience different climatic conditions with slight variations caused by microclimate. Climate responsive architecture incorporates design strategies to ensure the best indoor thermal environments under the prevalent atmospheric conditions. The hot and dry climatic zone (one of the six climate zones of India) requires special provisions for maintaining human comfort in buildings. Keep reading to understand the hot and dry climate zone in India, its characteristics and passive design strategies to combat the desert climate.
What is a Hot and Dry Climate?
The hot and dry climatic region can be found in western parts of India, such as Rajasthan, Gujarat and Northern Maharashtra. It is one of the six climate zones in India and is commonly called the ‘Rajasthan climate’ or ‘desert climate’.
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Typical characteristics of the hot and dry climate include:
- High Temperatures: The mean temperatures range between 27℃ and 50℃ during the daytime and 10℃-25℃ during the nights. Diurnal temperature ranges (difference in temperatures between the day and night) are very large, especially in winters.
- Low Humidity and Rainfall: Clear skies with little to no cloud cover mean that solar radiation is very high. Low relative humidity (below 30%) and minimal rainfall (below 250mm per year) can be observed.
- Winds: Dusty winds that carry sand and have high speeds (between 0.6m/s and 2m/s) are witnessed. Sandstorms are also common occurrences.
- Vegetation: There is sparse vegetation due to the low fertility sand typically present in these regions. The dry, open grounds further increase the heat as solar radiations get reflected and cause glare.
Architectural Design Objectives in Desert Climates
Architecture for hot and dry climate zones has the following goals:
- To reduce the indoor temperatures during the day (particularly in summers) and increase them at night (especially in winters).
- To divert, block or provide protection from strong and dusty winds and/or reduce their speeds inside.
- To introduce or increase the relative humidity levels to ensure optimal thermal comfort.
- To promote the growth of vegetation that can diffuse solar radiations and divert winds while improving indoor air quality.
Passive Design Strategies for Hot and Dry Climate
Architectural measures taken to improve the indoor thermal conditions without depending on mechanical ventilation systems are called passive design strategies. A few of these strategies that can be adopted for hot and dry climates are:
Building Footprint
- Built Form and Orientation: Compactly planned, inward-looking structures are the most suitable building forms in this climate. The larger sides of the building must face North and/or South. Surfaces facing the other two directions, particularly the West, must be minimised as they experience the maximum amount of solar radiation. Long, narrow buildings with the larger sides facing the North and South and having central courtyards can enhance cross ventilation.
- Planning and Zoning: Rooms that are not frequently used, such as bathrooms and storage areas can be located towards the West and East, where they will act as insulators that lower the heat penetration in other spaces. Neighbouring structures can be located close together to provide mutual shading.
Building Envelope
- Roofs and Walls: Thermal insulation can be improved by using heavy walls and roofs with multiple layers. Here, the time lag (time taken for heat exchange to occur between surfaces) is increased. This means that heat gained during the day is transferred inside at night, helping keep rooms warm and vice-versa. Using natural materials—such as rammed earth, cob, filler slabs with terracotta pots, and wattle and daub— to construct walls and roofs can also increase the time lag. High parapet walls around roofs should be avoided as they create stagnant pools of hot air.
- Openings: Since small openings can increase wind pressure and speed, large openings are more suitable in a hot and dry climate zone. However, these must have thick shutters with good thermal insulation properties to reduce the heat gain and transfer. Excessive glass must be avoided. West-facing windows must be avoided, and more openings can be given on the North side. Placing windows at higher levels will reduce high-speed winds in the occupancy areas (which are at lower heights).
- Shading Devices: All external doors, windows and other openings must be protected with shading devices like chajjas, overhangs and louvres to reduce the penetration of direct solar rays into the building.
Passive Building Design Measures
Many systems that have been a part of vernacular architecture for centuries can be combined with modern construction methods to make spaces more comfortable. Some of the ingenious design technologies that can be adopted are:
- Mashrabiya (Jaali Screen): These are latticed or perforated screens that can reduce wind speed and the amount of dust entering indoor spaces. Also called ‘jaali’ screens, these have been a common element of traditional Rajasthani Havelis.
- Evaporative Cooling: Evaporation of water causes cooling in the surrounding spaces. Including small water bodies in spaces like courtyards can help cool the air and also increase relative humidity, leading to better thermal conditions.
- Earth Berms: Berms are built structures that are partially or fully underground and surrounded or covered by earth. Also called earth-sheltered homes, these structures have cool indoor temperatures as the temperature of soil decreases with increasing depth. Vegetation can be grown on the mud covering the house, further providing insulation.
- Radiant Cooling: This technique involves using radiating or reflective surfaces to divert heat away from buildings. Using light colours on the roof and wall surfaces can help reflect heat and reduce its absorption.
- Traditional Shapes and Materials: Curvilinear forms like arches, vaults and domes, especially when made with natural materials, have better thermal insulation properties and help create comfortable indoor environments.
Climate Responsive Architecture & Building Services
Climate-responsive design and passive strategies are necessary for ensuring livable conditions in regions with a hot and dry climate. Leading construction companies in India, such as Brick & Bolt, employ experienced architects who customise plans for every project based on the climatic requirements of the region. These designs are then executed by qualified construction professionals who assure premium quality with 470+ quality tests. To get your dream home’s passive design optimised and built, get in touch with Brick & Bolt today!