Apurva Bose Dutta (ABD): In times when discussions on architecture and urban design revolve around sustainability and going green, glass has come across as a controversial building material in the Indian context. As someone who works on green building design and with glass to a large extent, what is your take on it?

Nilabh Nagar (NN): There is a lot of misunderstanding around the use of glass. The indiscriminate and irresponsible use of glass has resulted in buildings with larger energy consumption. However, that does not mean that we criticize the material.

Glass has very distinct endearing qualities, which can greatly enhance living spaces and human habitations, as well as the aesthetics of buildings. It allows transparency, ensures daylight and greater visual connectivity.

It also allows heat to permeate through, and hence, in our climate, needs to be adequately shaded to ensure minimal heat ingress.

It can also cause glare which can be controlled by the use of tint and coating. I think the advantages far outweigh the issues around it.

In my opinion, ‘green’ is a very misunderstood word. Are we talking here about green ratings or are we talking about energy-efficient buildings? It is true that excessive use of vision glass brings in heat.

But then, one has the option to have full glass buildings with varying amounts of vision glass, based on orientation and shading elements to maintain appropriate balance between light and energy.

The use of technology has given way to double glazing and coatings on glass which can attain the U-value equivalent to that achieved in a brick wall. Double skin ventilated facades can also achieve the same U-value, though at a higher cost.

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ABD: What are the technological innovations that you would like to see in glass in the near future?

NN: Unbreakable glass with transparency but no heat ingress would be wonderful to work with. It would also be nice to replicate the properties of the photochromatic glass we use in spectacles in architectural glass. Presently, the use of photochromatic glass in glass buildings faces the challenge of high cost factor.

ABD: Glass buildings are expensive. How do you take care of the cost factor of such buildings?

NN: Market forces automatically take care of that! Also, I believe that with time, we have become more responsible with our design and resources. The use of wrapped glass in commercial buildings is really dead, except maybe in the smaller towns where people are more desirous of aping the West and the metros; but then, that is only a small percentage of buildings we are talking about here. In metropolitan cities, especially the buildings of IT Parks, clients have developed energy consciousness and hence they use limited amount of glass, probably around just 30%–40%. New materials such as terracotta, acrylic solid surfaces, metal and chromatic back painted glass are being used in combination with regular brick mortar to make buildings look more interesting. In residential buildings, however, the proportion of glass has been quite constant.