The story so far: India is witnessing an unprecedented construction boom, with over 3,00,000 housing units erected annually. This growth brings economic opportunities and improved living standards but also poses significant environmental challenges. The building sector, a major energy consumer, accounts for over 33% of India’s electricity usage, contributing to environmental degradation and climate change. The India Cooling Action Plan forecasts an eight-fold increase in cooling demand between 2017 and 2037, emphasising the need for thermal comfort while reducing active cooling demand.
How can the construction sector become energy efficient?
Addressing energy inefficiency in residential buildings is crucial, given India’s rising energy and cooling demand due to economic growth, urbanisation, heat islands, and climate change. Initiatives like the Eco-Niwas Samhita (ENS) and the Residential Energy Conservation Building Code are steps in the right direction. The ENS introduces the Residential Envelope Transmittance Value (RETV), a metric measuring heat transfer through a building’s envelope. Lower RETV values lead to cooler indoor environments and decreased energy usage. For optimal efficiency, improved occupant comfort, and lower utility expenses, it’s recommended to maintain an RETV of 15W/m2 or less. However, current construction trends favour fast-paced, energy-intensive techniques with active cooling strategies, leading to compromises in thermal comfort. There needs to be more widespread knowledge about climate-appropriate design and architecture, with perceptions of high first costs as a barrier to the design and construction of climate-responsive buildings needing to change.
What materials are optimal?
Our analysis across four warmer climate cities in India highlighted the popularity of materials like Autoclaved Aerated Concrete (AAC) blocks, red bricks, fly ash, and monolithic concrete (Mivan). Despite concerns about sustainability, monolithic concrete construction was favoured by building developers for its speed, strength, quality, and scalability, with over 60% of buildings under design and construction phases opting for it, especially in high-rise buildings and skyscrapers.
The RETV evaluation for these buildings revealed that AAC blocks consistently had the lowest RETV across all climatic conditions, indicating their potential as a thermally efficient material. Based on literature review, a comparison of building materials for a 100 sq. ft wall area displayed substantial differences in embodied energy (the energy associated with the manufacturing of a product), with monolithic concrete having an embodied energy 75 times greater than AAC. When considering the estimated construction time for a 100 sq. ft room, red bricks required the longest time, while Mivan construction required the least. Mivan technology offered faster construction of buildings compared to traditional masonry work, particularly for taller structures.
Sustainability concerns are prominent across all materials. Red bricks exhibit moderate embodied energy, contributing to resource depletion, emissions, and waste. While AAC blocks have lower embodied energy, they still contribute to emissions and waste. Monolithic concrete, despite its quick construction time, presents the highest embodied energy, significant environmental impact, and sustainability challenges. Hence, AAC blocks offer a better balance between embodied energy and construction time than red bricks and monolithic concrete.
What next?
India has significant untapped potential for innovative building materials. Interdisciplinary collaborations with sustainability experts to delve deeper into integrated design and optimise strategies like building orientation, Window Wall Ratio (WWR), U-value (rate of heat transfer) of walls, roofs and window assemblies, glazing performance, active cooling systems, etc., can unlock the potential for a sustainable built environment. The construction industry’s preference for Mivan as a prime building material raises sustainability concerns, including high embodied carbon and thermal discomfort. Sustainable construction requires innovation from building materials manufacturers to develop cost-effective, scalable, durable, fire-resistant solutions with superior thermal performance and climate resilience. In conclusion, the journey toward sustainable construction is challenging but essential for a greener future. By re-imagining construction design and practices, manufacturing innovative walling materials, and fostering a culture of sustainability, we can create resilient and energy-efficient structures that align with environmental goals and significantly improve the quality of life for the masses.
Satish Kumar is President and Executive Director, AEEE. Stuti Goyal is Research Associate, AEEE and Dharini Sridharan is Senior Research Associate, AEEE.
- The unprecedented construction boom in India brings economic opportunities and improved living standards but also poses significant environmental challenges
- The building sector accounts for over 33% of India’s electricity usage, contributing to environmental degradation and climate change
- The India Cooling Action Plan forecasts an eight-fold increase in cooling demand between 2017 and 2037
