Building Cool and 'Climate-Smart' Indian Cities

India is in the midst of a ‘smart cities’ revolution and the ‘Smart Cities Mission’ promises to make cities more liveable, sustainable and resilient, but can this be achieved when cities are facing a series of challenges related to extreme heat? Dr. Komali Yenneti, in this article, identifies the technologies and strategies that can support governments at all levels in urban heat management. 

By Dr. Komali Yenneti

Sydney [Australia], April 30, 2019: All 15 cities listed as the world’s warmest by the El Dorado weather website last Friday were from India. Cities and regions from Maharashtra and its surrounding areas were among the hottest regions on earth on Saturday, with the recorded temperature at least 5 degree Celsius above normal. 

The last week heatwave that engulfed the cities and regions of Central India and its surrounding areas has seen heat records tumble like Jenga blocks. 

As the mercury climbed up, in some places such as Akola, Parbhani and Chandrapur districts in Vidarbha region, temperatures soared to 47.2 degree Celsius.

Heat is a serious concern, and those most at risk include the elderly, babies and young children, pregnant women, and people with existing medical conditions.

The historical EM-DATA data shows that the maximum number of heat wave occurrences and heat-related deaths in India occurred over the last five years.

Heat-related mortality increases by at least 10 percent at temperatures of 40 degree Celsius and above. In particular, the elderly surgical population is at risk of developing complications and prolonged hospital stay when peak outdoor temperature reaches above 30 degree Celsius.

The Indian Meteorological Department (IMD), the National Disaster Management Authority of India (NDMA), and other national and regional institutions now recognise high temperatures and extreme heat events as a serious risk to public health.

Cities heat up faster than the surrounding rural areas due to the Urban Heat Island (UHI) effect, a phenomenon caused by large dark concrete buildings, asphalt roads, closed structures, pollution released by vehicles, building air-conditioning and industrial output. Rapid unplanned urbanisation, greater urban sprawl, overcrowding, and reduced green cover only add to these issues.

The average temperature in highly urbanised areas is 2-12 degree Celsius higher than the surrounding rural areas.

Climate-smart interventions to cool cities and communities

The good news, however, is that a range of climate-smart strategies is available to manage the urban environment and cool cities.

These innovative solutions can be broadly categorised into two areas (i) solutions that decrease absorption of solar radiation and release of heat to the atmosphere and keep urban surfaces cool (e.g., reflective materials), and (ii) increase evapotranspiration in an urban environment (e.g., urban greenery and water-based systems).

1) Water-based landscape

The use of water in reducing outdoor temperatures has been known for many centuries. Water-based urban landscape, such as lakes, rivers, and wetlands contribute to urban cooling through water retention and evaporative cooling.

Water-based landscape can decrease urban temperatures by 3-8 degree Celsius. Apart from natural water bodies, a variety of passive systems and active or hybrid water components like pools, ponds and fountains, sprinklers and water fountains can be implemented in public spaces for both decorative and climatic purposes.

2) Urban greenery

Various forms of natural and designed urban greenery decrease urban temperatures and cool air through shading and evapotranspiration.

Urban greenery may be part of urban landscapes, parks, streets, and open spaces, and can also be integrated into the building envelope through green roofs and vertical gardens. 

In tropical and subtropical climate zones with sunny summer skies, like that of India, urban greenery is an economic and effective heat mitigation strategy. For example, increasing street tree and canopy cover by 14-40 percent can lower afternoon temperatures by as much as 5.5 degree Celsius.

To design urban green spaces with the greatest cooling effect in hot summer weather, architects and urban planners need to collaborate in design interventions.

3) Reflective materials

Reflective materials – also called cool materials - can greatly reduce extreme temperatures, increase thermal comfort and reduce energy demand in air-conditioned buildings.

Advanced cool materials with very high reflectivity and high emissivity are now commercially available.  The common cool materials are white and come in single ply or liquid forms.

The standard liquid products are usually white paints, acrylic, elastomeric or polyurethane coatings, while single ply products are EPDM (Ethylene Propylenediene Tetrolymer Membrane), PVC (Polyvinyl Chloride), CPE (Chlorinated Polyethylene), TPO (Thermoplastic Polyolefin), and CPSE (Chlorosulfonated Polyethylene).

Typical reflective materials used for street surfaces are fly ash (concrete additive), chip seal, slurry coating, reflective synthetic binders and light-colour coating. In recent years, researchers at the University of New South Wales (UNSW) Sydney have developed ground-breaking coloured thermochromic materials that become highly reflective at higher temperatures.

Through these materials, building owners do not require to compromise on aesthetics.

Reflective materials can be applied to the exterior surfaces of buildings (cool roofs and cool facades) or outdoor spaces (cool roads and pavements).

Cool roofs can reduce average summer indoor temperature up to2-5 degree Celsius in India. While reflective materials can offer significant opportunities to save energy and cool Indian cities, the lack of relevant policies and building codes can create challenging conditions.

4) Climate-responsive building design

The integration of climate-responsive building design and adaptive design techniques in existing buildings can reduce indoor and outdoor temperatures and significantly increase thermal comfort. Using urban greenery, artificial structures (e.g., temporary shades, sunshades, and shades using solar panels), or a combination of both on shopping streets, building entrances, and public spaces can prevent solar radiation and increase outdoor thermal comfort.

Policies pave positive pathways

Urban heat management has been an important policy agenda for Indian policymakers, though largely as part of the central government efforts on energy efficiency and climate change.

Some local governments have developed heat action plans in partnerships with state disaster management authorities, health departments and meteorological offices. However, these plans focus on ad-hoc emergency response, neighbourhood outreach and public awareness activities during extreme heat events.

Technologies are not simply absorbed and implemented through either a one-off policy or by one person. Relevant policies that bring together community, industry, and governments are crucial for wide-scale implementation of disruptive climate-smart technologies and their integration into mainstream urban policy. Image Credit - Author

(Dr. Komali Yenneti is the New Generation Network Scholar – Lecturer at the Faculty of Built Environment, UNSW Sydney and an Honorary Fellow at the Australia India Institute.)

Disclaimer: The opinions expressed in this article are the personal opinion of the author. The facts and opinions appearing in the article do not reflect the views of Indian Observer Post and Indian Observer Post does not assume any responsibility or liability for the same.

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