Beyond carbon: why water defines true net-zero in built environment

Bengaluru: As the global push for sustainable development gains momentum, experts in the building and infrastructure sector are calling for a broader approach to net-zero buildings that goes beyond carbon emissions and energy efficiency. According to B.O. Prasanna Kumar, NEC Member of the Indian Plumbing Association (IPA) Bengaluru Chapter and Joint Managing Director of DesignTree Service Consultants Pvt. Ltd., water sustainability must be placed at the centre of the green building movement.

Speaking to The Hans India, Prasanna Kumar said that while net-zero buildings are widely recognised for reducing carbon emissions through energy-efficient design, water conservation remains an equally critical but often overlooked component of sustainability.

“Buildings account for nearly 40 percent of global energy consumption and about 30 percent of water usage. If we focus only on energy and ignore water, the sustainability goals of the built environment remain incomplete,” he explained.

With rapid urbanisation expected to bring nearly 70 percent of India’s population into cities by 2030, pressure on water resources such as rivers, lakes and groundwater is set to intensify. Experts believe that efficient water management within buildings can significantly reduce environmental stress.

Prasanna Kumar emphasised that water, energy and carbon emissions are deeply interconnected. Treating, pumping and distributing water requires substantial energy, which in turn generates carbon emissions. Conversely, energy production processes often depend heavily on water resources.

“Saving water is also a way of saving energy and reducing carbon footprint. For instance, conserving one kilolitre of water can reduce approximately 0.8 kg of carbon dioxide emissions depending on regional conditions,” he noted.

Highlighting practical solutions, he pointed to a commercial building project in Bengaluru designed to achieve net-zero energy status while prioritising water conservation. The building integrates rainwater harvesting, greywater recycling and low-flow plumbing fixtures to drastically reduce water consumption.

Through rainwater harvesting alone, the building has reduced its dependence on municipal water supply by nearly 50 percent. Greywater recycling has cut wastewater generation by about 30 percent, while low-flow fixtures have reduced potable water consumption by nearly 40 percent.

“In total, the building saves around 25,000 litres of water every day, which is roughly equivalent to the daily water needs of nearly 100 households,” he said.

On an annual basis, the water conservation measures translate to savings of more than 9.1 million litres of water. Reduced pumping requirements also result in energy savings of approximately 13,687 kilowatt-hours per year, preventing nearly 11 tonnes of carbon emissions annually.