Refurbishing Heat Islands in Indian Cities

Indian cities are rapidly experiencing the emergence of heat islands. “Heat islands” are areas within cities where temperatures are higher than in other parts. The challenge we face is to reduce the temperature in these areas. This task involves renovating the existing urban environment, and the first attempt to do so was made by Scottish urban planner, Patrick Geddes, nearly 100 years ago.

When the British settled in India, they encountered unsanitary, noisy, and unpleasant conditions in the cities. Consequently, they constructed independent colonies outside the city, including cantonments for the military and civil lines for the officials and businessmen. The neglected Indian areas with deteriorating houses, unclean localities, congested narrow streets, and disregarded natural systems were left mostly unattended.

Geddes directed his focus toward these neglected Indian areas and developed plans to refurbish the urban environment in 18 Indian cities such as Lucknow, Tanjore, and Indore. The planning process followed a two-step approach: first, diagnosing the current state of the urban environment, and then upgrading it, which was labeled "diagnosis plus conservative treatment," drawing inspiration from medical science to cure human living conditions.

Drawing from this planning practice, below are some ways to refurbish the existing urban environment in Indian cities to address the issue of heat islands:

Areas with tall buildings

Indian cities are increasingly being densified, with the construction of tall buildings. However, these buildings, typically made of glass, steel, and concrete, tend to absorb a lot of sunlight. To keep them cool, using reflective glass and "cool roofs" is a common practice. Installing louvered sunshades, similar to London's Walkie Talkie skyscraper, helps maintain cooler temperatures. Another approach is covering the building's façade with plants, which creates a cooling effect by blocking the sun's heat and releasing water through evapotranspiration. This approach is successfully implemented in Tel Aviv, Israel.

Tall buildings can also be positioned to keep footpaths cool for most of the day, as well as reduce the risk of heat stroke and overexposure to people. Positioning tall buildings to block the sun from reaching the street during the morning and the afternoon creates what are called “urban canyons”. Buildings in Manhattan’s 5th Avenue, New York, are located in this fashion. Adding trees to urban canyons enhances this cooling effect.

Ripping out the first floor of tall buildings is another way, used by the Chinese in some coastal cities. The openings so created, allow the breeze to pass through and cool the surrounding places as well creating a place for people to walk.       

Dense market areas  

In crowded market areas, it's possible to reduce temperatures by designing pathways around buildings that align with sunlight and wind direction, providing shade and better airflow. Redesigning narrow roads can simultaneously improve walkability and pedestrian safety, a practice known as "sikkak" and commonly used in the Middle East.

Footpaths and other walking spaces

Footpaths and roads made of materials like bitumen and concrete tend to heat up under the sun. To counter this, using materials that reflect more energy than they absorb and porous materials for evaporative cooling is advisable. An unconventional method is to create vegetative pavements with lattice structures, allowing grass to grow.

Homes

Standard practices include painting walls and roofs with white paint to reflect heat and providing shaded structures in areas exposed to direct sunlight. Wind catchers, tall chimney-like towers attached to buildings, are also effective in increasing ventilation and cooling. These are commonly seen in the United Arab Emirates. Another method involves shaping building materials into blocks with air pockets to prevent heat penetration.

These methods of refurbishing existing buildings are known and being implemented in Indian cities on a limited scale. However, there is a pressing need to prepare a complete list of practices to reduce heat island effects in cities, and then roll them out on a large scale.

Furthermore, heat islands vary from city to city and within cities. Therefore, a mix of top-down and bottom-up approaches is needed to address this issue comprehensively by changing the building regulations, followed by the development of tailored plans for specific localities.