In 2018, the building industry in India accounted for over 30% of the total electricity consumption leading to 505 MMT of carbon emissions, and residential buildings accounted for 75% of the electricity consumed by the building industry. Residential buildings have a large exposed façade area to built-up area ratio, resulting in the space cooling load dominated by envelope heat gains. Typically, as a solution, room air conditioners are employed. The air conditioner market is increasing with the growing Indian economy. However, Energy Conservation Measures (ECMs) improve the building envelope, reducing the need for air conditioners. Eco Niwas Samhita (ENS) an energy conservation code for residential buildings in India recommends a Residential Envelope Transmittance Value (RETV) to limit the envelope gains. The literature indicates that there is significant potential to reduce the space cooling requirement of existing building stock by proposing deep decarbonization strategies. This paper focuses on upgrading the RETV of existing residential units across India. Retrofitting existing residential units to improve energy efficiency is a big challenge because it involves high investment costs and decision-making from a wide range of stakeholders. As per the ENS, the RETV compliant threshold value is 15W/m2. It is observed that for cities in different climates, i.e., Ahmedabad (hot-dry), Pune (temperate), Mumbai (warm-humid) and Delhi (composite), sample size with RETV above 15W/m2 are 66%, 25%, 65%, and 82%, respectively. The impact of insulation on space cooling requirements is highest in Ahmedabad whereas the impact of double-glazing unit is highest in Mumbai. Of all the ECMs, the best ECM (change in overhang depth + change in glass Solar Heat Gain Coefficient (SHGC) + change in wall U value) results in 67% energy savings and cumulative carbon savings of 10MMT across four cities.


I have graduated with Master of Technology in Building Energy Performance from CEPT University, Ahmedabad, India. As Sustainability Consultant and an Architect, my aim is to undertake analysis and provide solutions to attain sustainable, energy efficient and net zero building design. My interest also lies in evaluating the performance of green buildings, post their occupancy – to enhance its sustainability.