Architectural design must be based on the local climate to ensure that built structures are thermally comfortable for their occupants and users. A large part of Southern India is part of the warm and humid climate zone, making climate responsive architecture especially important here. Keep reading to understand the features of hot and humid climate in India and learn about the passive design features that can be used to reduce the negative impacts of this climate on residents.
What is a Hot and Humid Climate?
The warm and humid or hot and humid climate zone is one of the six major climate zones of India. Major portions of Southern India, particularly along the coastlines of both the Arabian Sea and Bay of Bengal and portions of Northeastern India, are a part of this climatic zone.
Warm and humid climate in India is generally characterised by the following features:
- Moderate to High Temperatures: Average temperatures during all the seasons range between 21℃ and 36℃. Temperatures during the day and night vary by around 5℃.
- Heavy Rainfall: Heavy rains can be witnessed during a major portion of the year- for around 7-8 months. The region’s rainfall levels are around 2000-5000mm per year. Cloudy conditions persist throughout the year.
- High Humidity: Relative humidity is constantly high—generally more than 75%—due to the proximity to the sea. The humid climate leads to extreme levels of sweating and thermal discomfort.
- Low Winds: Apart from local sea and land breezes, winds are either absent or minimal in regions with a warm and humid climate. When rare winds are experienced, they have a constant direction and very low speed.
- Vegetation: Due to the abundant rainfall, trees and plants grow well and dense vegetation can be observed in most regions with this climate.
Architectural Design Goals in Warm and Humid Climate
Passive design in hot humid climate zones typically aims to achieve the following objectives:
- To maximise natural light, but decrease internal temperatures throughout the year.
- Removing stale air to make way for fresh air by ensuring sufficient cross ventilation in all enclosed spaces.
- To reduce humidity and sweating.
- To provide adequate protection from heavy rains and prevent problems like water leakage and seepage, mould development and floods.
Fulfilling these objectives can lead to built structures that are thermally comfortable and provide a respite from external climatic conditions.
Climate Responsive Architecture for Warm Humid Climate
The following factors are considered for optimising building designs in the warm humid climate zone:
Building Footprint
- Orientation: The major wind directions are from Southwest-Northeast and Northeast-Southwest in this zone in India. Orienting the larger surfaces of buildings perpendicular to these directions can maximise air flow. However, the larger surfaces should avoid facing South and West as these directions can gain the maximum amount of heat. The North direction obtains the most favourable sunlight, and facades oriented towards this direction can have optimised indoor daylight quality.
- Planning: Long narrow structures—such as rooms arranged towards one side along a long corridor (which is ideally semi-open)—can have maximised cross ventilation. Traditional courtyard houses, with rooms arranged around a central courtyard, also have optimal air flow patterns. When there are multiple built structures, staggering them in both plan and height can enhance cross ventilation.
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- Form: With low-rise buildings, it is advisable to orient buildings based on the wind directions, as mentioned above. However, for high rise buildings, it is more important to prevent heat gain by avoiding large facades towards the West and South. All buildings must have a raised plinth to avoid penetration of rain water inside. Buildings raised on higher stilted platforms also have better air flow through them.
Building Envelope
- Walls: Lightweight materials with low thermal storage capacities are ideal for making walls in the warm and humid climate zone. Walls in enclosed spaces must be shaded by overhangs or semi-open spaces like verandahs and courtyards to reduce the heat gain.
- Roofs: Sloping roofs are a necessity in this climatic zone to ensure efficient drainage of rainwater. Large overhangs are also required to prevent water seepage inside the buildings. Roofing materials that do not store heat and can instead reflect it—such as terracotta tiled roofs—are ideal.
- Doors, Windows and Openings: Large openings can allow more air inside. However, smaller openings on the windward side enable higher wind pressures and larger openings on the leeward side (the side opposite to the windward side) allow this air to move smoothly. This effect of increased air pressure through small openings is called the Venturi effect.
- Shading Controls: All openings must be adequately shaded with chajjas, overhangs, louvres or other shading devices to prevent water ingress.
- Dehumidifiers: Plants and curtains made with natural materials that can absorb moisture—such as khus or vetiver grass—placed near openings can help reduce the humidity in the air.
Other Passive Design Techniques
Any measures or techniques adopted to reduce a building’s dependence on electrical and mechanical energy equipment, such as HVAC systems, are called passive design strategies. A few important passive design strategies for warm and humid climate zones are:
- Wind Towers: Also called wind scoops or wind catchers, these are tall structures that resemble chimneys. They trap cool breezes flowing at larger heights and divert them inside, allowing hot air to rise up and move outside.
- Reflectors and Light Wells: Incorporating skylights and light wells (elongated tunnel-like elements lined with reflectors that divert natural light to lower levels of a house) can increase the amount of natural light in enclosed spaces.
- Stack Effect: Also called the ‘chimney effect’, this method utilises narrow and high spaces—such as double-height ceilings—to enhance air ventilation. Openings placed at high levels (typically in the ceiling) suck out hot air, enabling cooler air to flow in through openings placed at lower levels.
- Natural Materials: Using natural materials that perform well in coastal areas—such as laterite bricks, thatched roofs and bamboo—reduces the heat absorbed through wall and roof surfaces and increases their breathability.
- Vegetation: Strategically located trees—such as in courtyards—can divert air into buildings. Plantation also helps absorb excess moisture from the air and prevents flooding from heavy rains by increasing the soil retention.
Implementing Passive Design Strategies
Careful analysis of the regional climate as well as conditions of the local micro climate is a basic necessity for ensuring good architecture in the hot humid climate zone. Brick & Bolt, a leading construction company in India, undertakes climate responsive design with the aid of its team of expert architects and construction professionals. The company has completed over 7000 homes with customised plans created for every project. Reach out to Brick & Bolt today to get your home built on the basis of climate responsive architecture and passive design strategies!