As India witnessed one of the warmest winters this year, the need for ‘cooling’ again hit the media headlines. Another major bulletin has been about the unprecedented changes in rain patterns leading to higher wet bulb temperatures, making conditions unbearable for human survival. Around 50% of India lives in the warm - humid climatic zone[1], So this is alarming. India is one of the countries with the lowest access to cooling in the world, and among all the sectors, the demand for ‘space cooling’ is expected to rise exponentially.
The lock-in period of a built structure is around 60-80 years, significantly higher than the life span of fans, lights, and air-conditioners which also influence indoor temperatures of built spaces. This piece, therefore, compares a few traditional and current architectural practices and discusses some design and technological innovations for building efficiency. It also sheds light on barriers to their adoption, and solutions that are currently being tried.
Traditionally, climate was central to the construction practices of India. Courtyards (of varying sizes depending on climatic region), high thermal mass[2] for wall insulation, and optimum window sizes were commonly observed features of dwellings. With the cultural influence of colonial bungalows, outdoor lawns became a preference over indoor courtyards. The rise in population, land politics, and space constraints resulted in many outdoor spaces being consumed in building more structures.
Walls (insulation) too grew thinner due to area constraints and with glass becoming a craze, windows grew bigger leading to more heat gain inside buildings. Glass has become an aspiration material worldwide, appreciated for enabling views and efficient daylight, but it is often overused causing a catastrophe in the tropical-subtropical climates like that of India.
Moisture-absorbing materials like mud bricks (adobe), and rammed earth were earlier used for walls in humid regions. Mangalore tiles, bamboo shingles, or coconut palms, often constituted their sloping roofs, as these regions experience heavy rainfall. With multi-storey construction and flat roofs becoming a custom these became obsolete, red-brick and concrete a standard. Brick and concrete are further being superseded with glass, aluminium, and steel structures- the popular symbol of modernity in advanced economies.
Research in cognitive science suggests that sight and aesthetics have governed architectural practice for many years, and it’s only recently that designers have begun to understand the importance of thermal comfort[3], sounds, and other multi-sensory perceptions for promoting good physical and emotional well-being. Designer/user behaviour is also influenced by aesthetics and the socio-cultural value of construction practices besides their affordability, or climate responsiveness.
While lack of awareness about technology and affordability are considered a hindrance to building climate-resilient structures, conflicting interests of stakeholders- material scientists, manufacturers, suppliers, architects, developers, and user preferences equally are barriers to the uptake of low-carbon materials and adoption of climate-responsive designs[SM1] . For instance- manufacturers work for profits unlike material scientists who work towards reducing carbon footprint, developers use materials that are user preferences, etc.
Warm-humid climate necessitates constant air circulation to control humidity and heat gain. Making narrow building floor plans and channelling wind properly by keeping smaller window sizes in a windward direction, larger in a leeward direction; or an inlet at a lower, and an outlet at a higher level helps in maintaining pressure-driven wind movement. As per climatic studies, keeping medium size openings of 20-40% of wall surfaces is advised to avoid moisture gain. High relative humidity in some months renders evaporative cooling[4] ineffective (which works well in hot-dry climates), and mechanical cooling systems (ACs) become essential to provide thermal comfort, in certain months.
Among building materials, in recent years, autoclaved aerated concrete (AAC) blocks, hempcrete, and agrocrete have been explored as potential substitutes for other carbon-intensive materials like red burnt clay bricks. Precast concrete, pre-engineered structural systems, and prefabricated sandwich panel assemblies are being piloted as durable as well as thermally-efficient systems of construction. Interventions in public institutional projects with these materials and methods could increase their social value and demand. Public procurement of green building materials could also trigger a reduction in costs, and potentially bring radical shifts in the preference and purchase of these materials in the market.
In January 2019, the Government of India’s Ministry of Housing and Urban Affairs (MoHUA) launched the Global Housing Technology Challenge (GHTC) to find and mainstream a variety of sustainable, and disaster-resistant building technologies from across the world for the housing sector. Successful lighthouse projects under the PMAY-Urban program show that it is possible to quickly upscale sustainable technologies. MoHUA has also recently launched a handbook on ‘Innovative Construction Technologies & Thermal Comfort in Affordable Housing’. These can serve as an inspiration for the builder’s community who are other dominant players in the construction industry. The Ministry of Environment, Forests, and Climate Change (MoEFCC) launched the India Cooling Action Plan (ICAP) in March 2019, which offers a 20-year vision to improve thermal comfort for all and reduce cooling demand. Some state disaster management authorities are currently looking at facilitating the implementation of ICAP. Additionally, National Disaster Management Authority (NDMA) released guidelines for preparing Heat Action Plans (HAPs) in 2017, which are preparedness plans to safeguard local populations from high heat. Several cities introduced cool roofs under HAPs which not only set an example for other cities but also inspired state-wide application in Telangana, which recently became the first state to introduce a state-wide cool roof policy.
The Bureau of Energy Efficiency (MoP) released design guidelines for energy-efficient multi-storey residential buildings (warm and humid climates) in 2016. The Ministry of Power (MoP), also published a set of codes called the ‘ECO-NIWAS Samhita (ENS), Part 1’ which defines minimum ‘building envelope design standards’ to improve energy efficiency and thermal comfort in residential buildings for different climatic zones. This was launched in 2018 as a sequel to Energy Conservation Building Code (ECBC-2017), which had covered recommendations for the commercial building sector.
The Energy Conservation Act 2022 has now included offices and residences in ECBC making it Energy Conservation and Sustainable Building Code (ECSBC). While many states have adopted these energy codes, effective implementation remains a challenge. Compliance with these can significantly improve the thermal performance of buildings and help fight climate change while providing benefits like reduced electricity bills and better physical and psychological health for residents. Decentralisation and improved collaboration across various levels of governance (nation, state, cities) are key for the implementation of these codes and for promoting the construction of climate-resilient buildings.
Pooja Gangwar works with the Clean Energy Program at World Resources Institute India, where she supports work in building sector decarbonisation, sustainable cooling, and clean-energy transitions. She holds a post-graduate diploma in Built Environment from Anant National University, Ahmedabad, and a bachelor’s degree in architecture from the School of Planning and Architecture, Delhi.
[1] India is divided into five distinct climate zones: hot-dry, warm-humid, cold, temperate, and composite. Prolonged patterns of homogenous weather – temperature, wind, and precipitation, characterise these zones. Warm-humid regions show consistently high temperatures, significant annual precipitation, moderate wind speed, and high relative humidity.
[2] Thermal mass is a material property to store heat, providing inertia against temperature fluctuations. Generally, thicker materials or cavity walls ensure good thermal insulation.
[3] Thermal comfort is achieved when body temperature is kept within specific range/limits, low skin moisture, and minimal physiological effort is required for regulation. Thermal Comfort - NZEB
[4] Evaporative cooling is the reduction in temperature resulting from the evaporation of a liquid, it is the principle on which conventional coolers work (Evaporative Cooling - NZEB) Sweating is also a biological evaporative cooling response for regulating human body temperature.