Can green buildings with net zero energy counter climate change?

  • 2 years ago
  • 1

India is at Number 5 on the Global Climate Risk Index 2020, according to CDP, an agency that creates statistics based on disclosures by organisations, cities and governments.

The Mumbai cyclone and floods showed the reality and magnitude of the problem. As did the severe first lockdown when nature rejuvenated and struck back with blue skies, clear waters and clean air. Thanks to this CDP says the level of disclosures have increased since 2020.

Buildings account for over 40% of global emissions. With increasing awareness, adoption of green practices have intensified. Over 1 billion sq ft of built-up space has been rated green by the IGBC in India. This movement has caught on even in the residential sector. Since 2015, when the IGBC announced its residential rating policy, over 18 lakh homes have been rated green so far. So much so that even affordable homes are now going for green ratings with lenders offering incentives to do so.

V Suresh, Chairman IGBC, says green buildings use passive design through correct orientation to harness the power of the sun – light without heat. So what do buildings have to do to let in the light and reduce the heat?

Orientation of the structure plays a major role. As does the protective cladding of buildings on the southern and western walls to reduce heat intake. Since India has clear skies 95% of the time, by letting in natural light there are significant energy savings. Cladding reduces heat intake by about 25-30% says Dr Prashant Reddy of Fundermax which specialises in exterior cladding. It acts as an external skin to the building and protects it from rain, heat etc.

The heat and glare can be reduced with the right level of fenestration,” says V Suresh, Chairman IGBC. The U and R values are measured to assess these scores. The National Building Code, the recommendatory document on construction norms in the country, has brought out a new chapter on glazing to set standards of usage of glass. The window to wall ratio of 40-60% can keep much of the heat out. Once the civil structure is appropriate, cladding brings thermal efficiency, protects the building and enhances its life, says Dr Reddy.

The trapped air between the wall and panel creates a system of air movement to reduce heat. At least three quarters of the wall should be covered for best results. The green building plus plus is net zero norm with the four critical components of energy, water, waste and carbon accounting for a net zero building.

While cutting out heat is good for the thermal comfort and energy usage in the building, letting in light enhances the productivity of the workforce or the occupants. Explains Gaurav Burman, APAC President, 75 F, “A lot of people have become a lot more sustainability oriented.” At a desktop level you need 350 lumens. If natural light gives 200-300 lumens, the system is made intelligent enough to figure out how to work the dimmers for optimal lighting and save energy. A three-pronged approach of measurement, control and the right kind of filtration and the systems to take care of it, takes building management closer to the Net Zero concept.

With wide adoption of these measures, climate change and its impact may not be fully reversed. But gradually the volume of energy consumed and the amount of building emissions reduced may have significant long-term impact on the sustainability index.

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