In the seventh in a series of features showcasing building materials, KC Jain, President, HNG Float Glass, talks about glass as a vital material for the construction industry.
'Extreme' seems to be the only constant as far as temperature is concerned. And in the construction field, temperature swings have deeper implications than choosing the right outfit for the weather: a warmer exterior demands that the cooler interior be intensified and vice versa. This requires electrical energy, a product of burning coal or fuel oil, nature's gifts that are on the verge of exhaustion.
Glass, being recyclable, is less demanding on nature. It has played a stellar role in our dining tables, windows, cupboards, doors, and even picture frames. But with time and advanced technology, its range of applications has increased further. Highlighting its use for architectural structures and interior decoration in conversation with Shriyal Sethumadhavan, KC Jain, President, HNG Float Glass talks passionately about this chemically inert, brittle, hard, transparent and crystal clear substance and its role as a vital material for the construction industry...
The manufacturing process
More than 1 tonne of natural resources can be saved for every tonne of glass reused. For every 10 per cent of cullet used in glass production, the cost of energy drops by nearly 3 per cent. And, every 6 tonne of cullet reduces more than 1 tonne of carbon dioxide emission. Thus, recycling glass provides for significant environmental benefits. It does not require any additional processing and is 100 per cent safe for reuse. The main ingredients of glass are high quality silica sand with low iron content, which is mixed with soda ash (a chemical ingredient) and minerals like limestone and dolomite. Once this mix is heated to very high temperatures, molten glass is formed.
Then-'n'-now
Over a thousand years ago, glass was made by hand; coloured glass was used in small sizes in churches and palaces. Later, as a solution to the scarcity of electricity, clear glass was used in windows to bring in daylight. Also, wooden windows with louvres were converted into small glass windows. In the early 1960s, with modern technology, glass could be manufactured with float technology, invented by Alastair Pilkington. Further, with technological advancement, safe glass, i.e. tempered glass, was manufactured. This glass does not break easily and is not harmful. In the present day, glass not only allows natural light into the building but saves it from heating up. For example, while the Low-E glass allows light, it restricts UV and IR rays, which generate heat, from entering the building. It is extensively used in developed countries like Europe and the US, unlike in India, where people have not yet understood the real use of glass as a building material and awareness is only up to 10 per cent of what it should be.
Producing heat
The normal heat energy produced from daylight comprises 44 per cent visible light, 53 per cent IR rays and 3 per cent UV rays that, combined, heat up the interior when sunlight passes through glass. An appropriate glass barrier can scale down heat energy and reduce power consumption by as much as 6 per cent and reduce both energy and maintenance costs to the extent of 28-30 per cent, especially when used in facades. This ultimately, has an impact on greenhouse gas emissions. Insulation is provided by various improvisations like placing a polyester film on glass or using tinted, reflective or Low-E glass. Therefore, the carbon footprint, which an organisation is obliged to keep in check to ensure a healthy environment, is reduced. Over a period of time, glass has evolved from being just a physical barrier to a material that has energy-efficient and safety features. It ensures comfort, light, ventilation and privacy; and by specifying the K-value of high performance glass, we can allow or restrict the desired amount of energy in a room or building. Its shading coefficient controls the amount of solar heat that enters. This is exemplified by insulated glass units (IGUs) that reduce heat without affecting light.
Functions
As an architectural material, glass is beautiful, UV-resistant, heatproof and requires zero maintenance, except for cleaning. It is a prefinished material that req-uires no further processing on site. It can be made tinted, reflective, opaque or completely transparent, soundproof and bulletproof. Modern structures use glass walls as a façade, which is not only appealing to the eye but reduces the temperature by 6° C. Also, acting as a mirror for heat, reflective or Low-E glass reflects sunrays. Toughened glass made by heating and cooling a sheet of glass in quick succession is the safest form. It acquires a strength equivalent of four to five times that of normal/annealed glass. Further, even after breakage, it does not leave dangerous sharp edges as it disintegrates into small granular pieces without hurting anybody.
Advantages of glass
Compared to concrete or any other construction material, glass is very light. If a building is made of glass, the total foundation cost reduces; the weight is about 30 per cent of that made by concrete. Moreover, glass acts as a safe building material giving a sense of space. Buildings in earthquake-prone countries are made of glass as it delivers a structure strong enough to sustain such calamities. Also, consider the climate of Dubai. It has a temperature of up to 49° C, yet glass is used in towers all over. Again, a building in Barcelona, Spain, that is bent at an angle of about 45° still stands tall. Glass is one of the few materials that can create such miracles.
Glass is normally used in combination with wooden, aluminium frames or steel structures. In steel structures, it is fixed inside an aluminium or steel frame and can be reused by removing it from the steel bars. But, this is difficult in the case of RCC, in addition to being very expensive. Even in manufacturing the most basic glass, 20 per cent of the raw material used is broken glass, reducing them material taken from the environment. The smallest particle can be put in the furnace and again converted into glass without loss of even 0.001 per cent. So, this green material uses less energy. And while the best advantage is that the customer
can decide what he wants, there is a misconception that glass is a breakable or fragile material - this works as one of the biggest disadvantages.
Addressing a concern
Nowadays, builders in Maharashtra are concerned about the usage of glass as a construction material and how it creates heat within the building. But, this is only relevant to clear glass as it does not filter any ray from the spectrum. Low-E glass absorbs and filters visible rays and re-radiates harmful rays into the atmosphere, leaving the heat outside. And double glare units (DGU) combined with Low-E glass amount to a saving of up to 24 per cent of electricity in the building. DGU windows are hermetically sealed and remain strong for 20-25 years. These units are made of two glasses, one of which can be a reflective or Low-E glass and the other a normal clear glass, hence producing a temperature difference of about 6-7° C from the outside.
The challenges
Glass is available all over the world, and even a growth in consumption will not affect availability. In terms of cost, it could be a little more expensive compared to other building materials, but it pays back very soon and does not require any periodic maintenance. A cement wall requires at least 10 inch of floor space, while glass requires half an inch. Hence, this material helps maintain a 10 per cent higher carpet area in a building. Moreover, as against a glass wall, which requires only about two hours to be installed, a concrete wall requires at least five to six days. The challenge lies in convincing the client that despite a heavy initial investment, it is supported with good payback. A green building, compared to a normal building, will incur about 8-12 per cent additional cost for glass and other chosen materials. But if you can save up to 25-27 per cent in lighting and air-conditioning, this investment is paid off within one-and-a-half to two years, hence making glass economical.
Future-friendly
Glass can be termed as the future of construction materials when all other materials get exhausted. While steel may rust eventually, corrosion does not affect glass. Materials like cement/steel require limestone/iron ore and other minerals in high quantities, and although this is the case with glass, the quantity is much lesser and these materialso can be retrieved, reused and refabricated into glass sheets. It is important for builders, architects, fabricators and consultants to realise the advantages of glass. Glass can be used in stairs, ceilings and walls and even in shower cubicles, where it can be spray-painted to acquire opacity. At present, the per capita consumption of glass in India is only 1 kg, whereas in China it is 12 kg. Its use as a construction material can grow at least 10 times in the next 10 years. And on observing modern buildings, I see a lot of scope for glass for both facades and partitions. But it is important to know its hidden benefits.
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