We can’t seem to have enough of glass. It has become the symbol of modernity. And with good reason too. It is a versatile industrial material, lets in light through windows, lets us see through (or not, depending on whether it is translucent) and makes for shiny, clean surfaces and building forms.
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For many people, especially in the corporate world, it is also a symbol of functionalism. The most common argument offered in its favour in this regard is that it allows natural light into interior spaces during the day. This saves energy and money by reducing electricity consumption.
But does it actually work that way? Is the glass curtain-wall (a continuous curtain of framed or connected glass sheets fixed to the structural frame) more about style than about saving money or the environment?
Most importantly, what portion of buildings—even in “developed” countries with cold climates, such as the US—actually use glass in a way that maximizes benefits and minimizes costs?
“A very, very small portion,” says Prasad Vaidya, an architect and energy analyst with The Weidt Group in Berkeley, California, who advises building professionals on energy matters.
As a broad rule of thumb, Vaidya suggests that the proportion of glass areas in windows must be kept between 12 to 25% of the total floor area in the US, so that interior spaces do not get overheated.
If that is ideal in the much-colder US, what’s with all the full glass towers in scorching Gurgaon (or Hyderabad)?
Glass and climate
Climate is important when thinking of glass in buildings. Glass is valuable in buildings fundamentally for its transparency, which lets in natural light. Hence its regular use in windowpanes.
But glass also lets in heat along with the light. And it allows only light to reflect back, trapping the heat inside.
Fixed glazing (or fixed panels of glass, as in picture windows in homes, or the large curtain walls on commercial buildings) on building exteriors thus helps create a greenhouse effect. When the curtain wall faces the west, it lets in the hottest sunlight of the day and turns the interior space into an oven. Of course, the simplest solution is to open the window. But windows clutter the smooth look of the curtain wall, and for that reason are not enthusiastically provided by architects.
In the heat of India, this means that the air conditioning works harder and costs more in terms of installation and electricity bills (while also emitting ozone-depleting chemicals such as chlorofluorocarbons). Of course, the more conspicuous the consumption, the more status it buys. A glass tower broadcasts the ability of the owner-occupier to pay for all this.
Reflection of modernity