Bengaluru misplaced love for glass walls

Minimising glass in construction is essential from a climate perspective, but the government has not framed rules for its fair usage.

“Every light switched on in Bengaluru, let alone the city’s millions of air conditioners, will have an impact on the environment. So, there is a need to build awareness among all, from a layman to builders and senior officers,” says Jagan Kumar, a businessman from East Bengaluru.

Determined not to allow his activism to be short-lived, Kumar filed a petition before the National Green Tribunal (NGT) seeking directions to frame rules restricting the use of glass facades and to take action against buildings in the city with more than 40% of their area covered by glazed facades.

In the petition, he cited a paper by T V Ramachandra and others of the IISc’s Energy and Wetlands Group showing that the per capita electricity consumption in the zones dominated by high-rise buildings with glass facades ranges from 14,000 to 17,000 units per year compared to zones with eco-friendly buildings (1300–1500 units/person/year).

In its response, the Ministry of Environment, Forest and Climate Change (MoEF&CC)  submitted that while it issued guidelines in June 2015 limiting glass facade to 40% of the exposed area, "these guidelines are advisory and un-monitorable in nature" and left the adherence to developers.

The tribunal in January 2025 noted that the National Building Code by the Bureau of Indian Standards and the Energy Conservation Building Code by the Central Pollution Control Board provide a framework to address broader concerns of energy conservation.

However, it set a three-month deadline for the MoEF&CC to constitute a committee comprising stakeholders to develop guidelines for the use of glass facades. "Over 10 months later, nothing has been done. I have written to the authorities, but haven't received a response. I will move the tribunal soon," Kumar told DH.

Quick fix, quick revenue

Suresh Hari, the immediate past secretary of the Confederation of Real Estate Developers' Associations of India-Bengaluru, noted that glass facades are limited to commercial buildings, ranging from regular office space to IT companies.

“Curiously, both the capital cost and maintenance cost of a glass facade are considerably higher than a brick-and-mortar wall with windows. Builders go for it because it’s a quick job. Once the work is done, the rent collection begins and allows recovery of all the costs,” he noted.

Many builders are aware that energy-efficient buildings not only cause less harm to the environment but also save money. Big players of the Indian corporate sector follow and reinforce such knowledge. Back in 2023, Infosys released a report, 'Pioneering Net Zero Buildings', stating that an integrative design approach, including reducing glass facades, helped reduce annual energy consumption from 25 million kWh to 8 million kWh, saving Rs 10 crore.

Suhail Rahman, Managing Director and Chief Executive Officer of CoEvolve Estates, believes the continued love for glass facades was also due to a veritable herd mentality.

“There is no doubt that brick and mortar is the most efficient in terms of energy performance. Though there is a nascent trend among big companies to adopt hybrid measures, much of the industry goes against such trends. Essentially, they are impressed by the glazed looks from the streets of Shanghai and New York. Add to this the idea of early project completion, the circle is complete,” he said.

Kumar noted that the state environment impact assessment authority (SEIAA), which grants environment clearances for buildings with built-up areas up to 20,000 sq metre, had limited glass facades to 40% of the exposed area for a new building in 2016. However, the condition was later removed without explanation, allowing thousands of newer buildings to use glass facades without limitation.

The larger picture

According to Power Corporation of Karnataka Limited, the state's peak energy demand is projected to double from 16,000 MW in 2024-25 to 33,000 MW in 2034-35. Of the 31 districts, Bengaluru Urban alone accounts for 25% of the total energy demand. The share is set to increase, thanks to the increasing development across the city.

While Karnataka prides itself on solar energy, it is tapping the Western Ghats, a biodiversity hotspot, to build pumped-storage projects as an alternative to battery storage facilities.

All this may seem like “green” energy just because coal isn't burned to turn the turbines. But the damage caused by power projects to the Western Ghats' ecology, whose role in Karnataka’s water and food security is well known, will be felt in the near future. Reducing energy consumption through guidelines that have already proven effective is therefore seen as low-hanging fruit.

Some builders believe that the recent emphasis on green building certification and potential incentives may help boost the adoption of energy efficiency measures. Among the several green building certificates is the one issued by the India Green Building Council.

IGBC Bengaluru Chapter co-chair Anup Naik said their Commercial Projects Rating System places strong emphasis on overall building envelope performance, positioning glazing as a critical determinant of energy efficiency, daylight quality, visual comfort, and occupant well-being. 

He said the first preference is for natural daylighting, which forms a major scoring avenue within IGBC, requiring 50–75% of regularly occupied spaces to achieve daylight autonomy. The IGBC framework integrates prescriptive benchmarks and real-world lessons to ensure glazing choices reduce cooling loads and enhance daylight. 

“IGBC recommends maintaining a Window-to-Wall Ratio of ≤ 40% and in cases where higher transparency is desired, insists that projects demonstrate superior envelope performance through better insulation, reduced solar heat gain coefficient and effective shading strategies,” he said, adding that the IGBC looks at the matter holistically and does not discourage use of glass facades. 

Climate challenges

In its recent report, Climate Compatible Futures stressed the need to incorporate peak power demand into the design of heat action plans, given the increase in days with higher temperatures. The peak power demand also increases emissions, with the study pointing to a 78.8% decadal increase in Karnataka.

In June this year, the Union government announced a plan to limit air conditioning settings to a minimum temperature of 20 degrees Celsius and a maximum of 28 degrees Celsius, to reduce electricity load and refrigerant use.

Interestingly, Karnataka's Energy Conservation and Energy Efficiency Policy 2022-2027, notified by the government in February 2022, also suggests mandating that air conditioners be set at 24-25 degrees C in all government and public offices. Further, it prescribes amendments to energy conservation building codes to suit regional and local climatic conditions. It recommends introducing the power of inspection of buildings to verify compliance with the law. 

Seen from multiple perspectives, energy-efficient green buildings seem to be the need of the hour. An official noted that even retrofitting the old buildings, during renovation works, would help reduce power demand. However, the gap between science and policy persists.

Need awareness

Divya Davis, a senior analyst at the Climate Mitigation Group at the Centre for Study of Science, Technology and Policy (CSTEP), said there is a need to examine the practical implementation of the rules.

"More than the gap between science and policy, we need to take note of the chasm between existing rules and their implementation. There are building codes, such as ECBC, that prescribe energy conservation guidelines, including passive design strategies like high-performing glazing and improved wall-to-window ratios. However, these are not implemented in most of the projects," she said.

She further pointed to the lack of awareness at the ground level. Many architects and contractors who take up the construction of such buildings may not be aware of the nuances of building codes, she added.

Why glass may not suit Bengaluru

Climate mismatch: Glass facades are designed for cold Western climates to trap heat. In Bengaluru’s tropical savanna climate, they act as greenhouses, trapping solar radiation and turning interiors into ovens.

Loss of natural cooling: Glass walls eliminate natural ventilation, making the city's famed "pleasant weather" irrelevant indoors.

Heat island effect: Glass facades reflect intense sunlight onto neighbouring buildings and streets, raising the ambient temperature.

10x power usage: IISc studies show that glass buildings in Bengaluru consume up to 10 times more electricity than conventional buildings due to air-conditioning loads.

Water stress: Glass facades quickly look dirty. Cleaning them requires frequent use of thousands of litres of water in a city already stressed by water scarcity.

Bird collisions: Reflective glass confuses birds; they mistake the reflection in the glass for real trees and fly into it at full speed. The Avian and Reptile Rehabilitation Centre in Bengaluru has previously reported bird injuries and deaths caused by glass.

Glass glare: Commuters on roads like the Outer Ring Road (ORR) often face blinding glare from glass towers during peak morning/evening hours.