India is divided into five major climatic zones.– Hot-Dry, Warm-Humid, Composite, Temperate, Cold.
As mentioned in the U.S. Department of Energy (https://www.energy.gov/), A hot-dry climate is generally defined as a region that receives less than 20 in. (50 cm) of annual precipitation and where the monthly average outdoor temperature remains above 45°F (7°C) throughout the year.
Hot and Dry Climate Regions in India
- Gujarat (Eastern Part)
- Madhya Pradesh
- Maharashtra (Central Part)
A hot and Dry climate is seen in western parts of the country where desert-like conditions exist. Jaipur, Jaisalmer, Kutch, Gujarat, and Parts of Maharashtra are the regions that come under this climate zone. In this article, we discuss important design approaches and strategies for hot and dry climate zones.
Characteristics of Hot and Dry Climate
- Temperatures: Very hot weather in summer and cold in winter
- High temperatures – Daytime summer temperatures often reach 40°C and can sometimes rise up to 50°C. In the winter, minimum temperatures vary between 5-25°C.
- High diurnal temperature range (High-temperature difference between Day and Night) – These hot regions have a wide temperature difference between day and night.
- High Solar Radiations
- Hot Winds
- Rainfall: Annual rainfall in hot and dry climate regions is as low as 250mm per year. In deserted areas, there can be long periods of drought.
- Humidity: Low Relative Humidity: These areas have low humidity levels that result in dry and arid conditions. The dry air further leads to rapid evaporation of water.
- Winds: Dusty winds often develop into sandstorms.
- Groundcover: Dry sandy or rocky ground with less vegetation
- Sky Condition: Cloudless sky
Objectives of Designing Buildings in Hot and Dry Regions
Since the temperatures are very high in hot and dry regions, the corresponding strategies are:
- Bring down ambient air temperatures
- To reduce heat transfer during extreme temperatures (hot in summers and cold in winters)
- Reduce the amount of direct solar radiation received by the building.
- Provide adequate shade
- Reduce exposed area
- Increase humidity
- Preserving vegetation
- Conserving water
- Use evaporative cooling
12 Important Design Strategies for Hot and Dry Climate
Let us explore the 12 most important design strategies for hot and dry climate zones.
1. Building Orientation
Since the design aim is to reduce the exposed area to direct solar radiation, and the Sun moves from East to West, the longer walls of the building should face North and South. The building gets minimal exposure. Building orientation also affects the amount of natural ventilation it receives.
2. Plan form
The plan form of the building affects the airflow, ventilation, and direction of air movement. The heat gain and heat loss depend on the perimeter-to-area ratio of a building. The greater the ratio, the greater the heat during the day and the greater the loss at night. Similarly, the smaller the ratio, the lesser will be the heat gain during the day and less heat loss at night.
The primary focus is to decrease heat gain in hot and dry climates, therefore, careful activity zoning related to habitable areas and service areas have to be properly zoned regarding the building plan form ensure heat gain reduction and optimum daylighting.
Appropriate placement of service areas can act as heat or thermal barriers.
4. Building Types – Low/High rise/courtyards
The design strategy also includes whether the building is a low rise or a high rise. Buildings that are low-rise have a higher footprint, whereas high-rise buildings have the least footprint.
5. During Construction – Practices
Design strategies for hot and dry climates are even required during construction practices to preserve vegetation, conserve soil, and reduce air pollution.
- Protecting the roots from excavation.
- Preserving existing trees with tree guards.
- Providing a sedimentation tank to collect and reuse rainwater.
- Pre-planned path for movement of materials and labor.
- Preservation of topsoil by temporary plants/grass.
- Placement of barriers to reduce air pollution and spread of waste materials.
Tress prevents infiltration of dusty winds of hot summer. Preserve existing trees as they are
- Fewer trees in the north to let in the daylight.
- More trees on the NW and NE to cut off summer radiation.
- Deciduous trees on the south side for shading in summer and solar access in winter.
7. Openings and Shading
Orientation and Shading are important factors in reducing heat gain and are significant factors in design strategies for hot and dry climates. Shading of windows is necessary for effective daylighting and to cut down heat.
- Shading of opening and wall by jali screen
- Shading of building surface by plantation.
- Installing double-glazed units
- Shading of building surface by texture.
- Shading by architectural projections.
8. Passive Cooling Strategies
Passive cooling strategies have to be implemented at the design stage itself to minimize energy loads. Some of the passive cooling strategies are:
- Water bodies near the structure, or inside the courtyard, and have to be shaded.
- Ventilation of buildings at night
- Central wind tower
- Earth berming
9. Building Materials
The selection of Building Materials is an important factor in the design strategies of hot and dry climates to save trees and vegetation, reduce air pollution, and utilization of lower embodied energy.
- Stones – obtained from sustainable sites – less air pollution and reuse of resources.
- Concrete blocks – use of stone dust and chips – reduces air and land pollution.
- Salvaged timber – saves trees by reducing the use of new wood.
- Fly ash blocks – lower embodied energy value – more efficient
- Stabilized earth blocks – lower embodied energy value – more efficient. Other materials include waste glass, marble chips, terrazzo, etc.
- Use of low-VOC Paints
Building walls and materials chosen can reduce heat transfer through walls. Walls with sustainable materials and insulation can act as heat barriers.
Building roofs and materials chosen can reduce heat transfer through walls. Roofs with sustainable materials and insulation can act as heat barriers.
12. Energy Efficiency strategies
Various design strategies for hot and dry climates related to energy efficiency include –
- Control the amount of heat reaching the building.
- Building orientation
- Shading by projections
- Minimize carriage of heat by building skin
- Reduce internal heat gain and improve daylight
- Use of fixtures with low equipment power density
- Outdoor equipment has to be shaded
- Use efficient artificial lighting
- Cooling the building
- Passive cooling strategies
- Low-energy HVAC technologies
- Solar photo-voltaic installation
- Provision of Solar water heater
- Rainwater harvesting systems
- Decentralized wastewater treatment systems