Extreme weather is forcing cities to rely more on energy-intensive adaptations, straining power grids and increasing carbon emissions. Global greenhouse gas (GHG) emissions have been on an upward trajectory marking a 0.8 per cent rise from 2023. The energy sector is responsible for 75.7 per cent of total emissions with residential buildings accounting for 12.5 per cent of emissions globally. The growing intensity and frequency of heat waves are pushing environmental and human thresholds to alarming levels, further increasing residential cooling requirements. Currently, residential cooling accounts for approximately seven per cent of India’s electricity consumption. This raises a crucial question: How can cooperative housing models contribute to climate sustainability?
The concept of green and sustainable living has gained significant attention worldwide, and India is no exception. There is a growing buzz in the real estate sector on the concept of green homes as a key driver of change. Green retrofitting involves upgrading existing buildings to enhance their sustainability and environmental performance, focusing on energy efficiency, water conservation, and resource management.
Take, for instance, the climate action plan for Mira Bhayandar, which aims for a 36 per cent reduction in emissions through the adoption of renewable energy sources, energy-efficient measures for buildings, and improved waste management practices. In 2023, the district consumed approximately 1,075 Gigawatt hours (GWh) of electricity, with the residential sector alone responsible for 62 per cent of the electricity consumption, accounting for 40.5 per cent of energy sector emissions.
A cornerstone of this climate action plan is the success of one of their own societies that pioneered a scalable retrofitting model. Retrofitting involves introducing modern materials and technologies to existing buildings to increase the building’s performance in terms of energy and water efficiency. The Nav Yuwan Housing Society managed to achieve over 60 per cent energy efficiency improvements where each household spent approximately Rs 17,500 ($200) for retrofitting.
The viability of the model ended concerns that the housing society had about affordability, implementation complexity, and long-term maintenance of climate-resilient solutions.
Nav Yuwan Housing Society in the Mira Road neighbourhood of Mumbai houses over 280 families and was originally constructed in 1994-95. An on-site energy audit assessed the energy demands of each apartment unit, including appliance usage patterns and peak demand analysis. This data collected and meter readings determined baseline consumption to optimise solar energy integration.
To this end, a 44 kWp solar photovoltaic system comprising 4 units of solar panels was installed, spanning a total area of 206 square metres. The solar energy system is projected to generate approximately 66,044 kWh of electricity annually, even after accounting for efficiency losses. Given the society’s average annual electricity consumption of 1569.6 kWh per surveyed unit, the solar panels will offset grid dependency, making the society more self-reliant in energy production. The solar PV system accounts for approximately 3.5 per cent of the overall energy savings in society, with the annual cost savings estimated at Rs 7,20,000, and a 3.9-year payback period indicating recovery of initial investment within a short span.
The electricity generated will primarily be used for common lighting purposes, with any surplus electricity being sold back to the grid, creating an additional revenue stream for society. The solar energy intervention at Nav Yuwan Housing Society underwent an EDGE (Excellence in Design for Greater Efficiencies) analysis to measure its environmental and financial performance.
Energy efficiency is not a matter of preference but a necessity. The installation of 1000 energy-efficient Brushless Direct Current (BLDC) fans, costing Rs 1,568,000, resulted in annual savings of Rs 1,602,496, achieving a short payback period of 0.98 years.
150 motion sensor-based dim tube lights are installed in staircases, lift lobbies, and the mid-land areas of the building. These lights remain dim when areas are unoccupied and switch to full brightness upon detecting movement, enhancing safety and comfort while minimising energy consumption.
The kitchen gardening initiative promotes sustainable waste management, urban agriculture, and green spaces. Specialised training sessions for senior citizens on best practices in soil management, composting, plant care, and efficient water usage promote knowledge building and impart a sense of ownership and community bonding among residents.
Attaining sustainability in the built environment requires a comprehensive approach to building retrofits. Green retrofitting measures align financial benefits with ecological well-being. It promotes energy efficiency, resulting in reduced energy consumption and lower utility bills for homeowners, and reduced emissions. Frameworks like EDGE have been successfully applied to evaluate green retrofitting projects in diverse settings.
With rapid urbanisation and the increasing spread of residential and institutional buildings, architects and urban planners must prioritise retrofitting over demolition of the buildings — to minimise waste, pollution and carbon footprints. As the world tracks its transition to a green economy and moves towards renewables, it is critical to focus on multiple ways to curb emissions in a world that is constantly heating up. As renewables reshape the energy sector and electric mobility revolutionises transport, green retrofitting is the logical next step for buildings. Nav Yuwan Housing model serves as proof of concept, demonstrating how green retrofitting can transform existing residential spaces into cost-effective and climate-resilient models. Beyond housing societies, schools, commercial complexes, and institutional buildings are also emerging as key spaces for energy-efficient upgrades. Implementing cool roofing, natural ventilation, solar panels, and smart lighting systems not only reduces operational costs but also creates healthier and more conducive learning environments. Scaling green retrofitting as a city-wide strategy is a step towards climate-proofing urban growth.
Prerana Langa is the CEO of Aga Khan Agency for Habitat, India, and Nayani Khurana is Manager, Knowledge Management at Aga Khan Agency for Habitat, India
Views are authors' own and do not necessarily reflect those of Down To Earth