MC Explains|Are glass façades in Bengaluru skyscrapers contributing to global warming and climate change?

At a certain juncture, Bengaluru's green stretch comes to an end and tall glass boxes shoot up in the sky, glimmering magnificently in the scorching blaze of early summer afternoons.

Though hard to estimate, the number of glass skyscrapers in the city has increased substantially over a decade, experts say.

Wrapped in a contemporary design, these glass façades house lakhs of employees working in the tech capital.

However, their glaze is now under the glare.

The National Green Tribunal (NGT) has sent a notice to Karnataka state government bodies to submit a report on the usage of glass façades that allegedly cause global warming and lead to climate change.

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Sub Editor|Moneycontrol

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The complaint filed by social activist Jagan Kumar points to a study conducted by the Energy & Wetlands Research Group Centre for Ecological Sciences, Indian Institute of Science. According to the study, using glass façades leads to an increased energy consumption of 14,000 to 17,000 units (kWh) per person per year from 1,300 to 1,500 units per person per year in eco-friendly buildings, almost 10 times more.

Rise of glass skyscrapers in the city

In the early 2000s, the city saw a major IT boom, with several multinational companies moving into the city.

Hariharan Chandra, a senior fellow at Indian Green Building Code (IGBC), Bengaluru chapter chair said the companies had principal architects from the US or other parts of the world.

"They felt that the glass curtains were more acceptable for rentals and also adorned a modern outlook. And it boomed over the next decade between 2010 and 2020," Chandra said.

Harsha Sridhar, principal architect, Initiative for Green Habitat added that often with high-rises, one of the major challenges is to make the structure lightweight and also earthquake-proof. "All these made it attractive for architects to quickly adopt the glass-fitted buildings for office spaces or large developments," he added.

Behind the glass

Dr TV Ramachandra, a scientist at the Indian Institute of Science, said this architecture is meant for European or temperate climates. "In Bengaluru, we need heat resilient buildings that have a low carbon footprint.”
However, glass installations take up less space and give the benefit of additional carpet area," he said.

Chandra added that construction time for glass-fitted buildings is lower compared to standard buildings. "It takes 3-6 months less time and also does not involve wet work in the civil construction, which requires more workers and also is a hassle for highrise constructions," he said.

Gains apart, experts say the major impact comes in the consumption of energy.

Data from middle eastern consultant firm UVK Associates that analysed several industrial, IT and hospitality establishments, accessed by Moneycontrol shows, in the hotel sector, the AC and the cooling system consume 49 percent of the total energy consumption. The industrial sector consumes 24 percent and the IT sector consumes a whopping 70 percent of the total energy consumption including AC and cooling pumps.

Chandra said, "On top of AC to cool the interiors, we need a cooling system — air-based or water-based. While air-based cooling systems will consume more energy, water-based systems require about 36.5 million litres of water for 1 million square feet of development annually."

Additionally, the glass-fitted buildings develop heat sinks between them thus raising the ambient temperature at least by 7 degrees.

Experts say this has had an indirect effect on scorching city temperatures and high rainfall for over 8 months in Bengaluru.

"It all boils down to carbon footprint and global warming. We need to use efficient construction materials and also design techniques to suit the local climate," Sridhar added.

National Building Code 2025 revision, other regulations

During the NGT hearing, on March 30, the Central Pollution Control Board (CPCB) submitted to the tribunal that the Ministry of Environment, Forests and Climate Change has framed the draft guidelines for Environmental Guidelines or Buildings.

"Use of glass be reduced by up to 40 percent to reduce the electricity consumption and load on air-conditioning. If necessary, use high-quality double glass with special reflective coating in windows," the written submission said.

Additionally, Section 8 of the National Building Code speaks about glass and glazing, however, does not specify the mandates during construction.
Though Energy Conservation Building Code (ECBC) sets minimum energy standards for new commercial buildings, however, Chandra said it is still voluntary compliance.

"From IGBC, we try to ensure every building has 15-20 percent energy efficiency and 30-50 percent water efficiency. We guide the promoters or architects, however, we are a certifying body. And most importantly we need to understand the green certification relative to certain baseline parameters," Chandra added.

Vijay Dahiya, architecture partner at Team3 added that most of the demand for glass façades is market driven. "We do have alternatives like low-E glass that are glazed and reflect heat. However, again this works best for shaded areas or portions that do not receive direct sunlight. High-performance glass is also available. However, it is much more expensive."

"The NBC revision of 2025 will reflect contemporary technology shifts in Part 4, 8, and 9," Chandra told Moneycontrol.