Reflections on glass

Use of glass in construction has become a fad. But it is not the right choice for Indian climate

 
By Disha Singh
Last Updated: Sunday 07 June 2015

Reflections on glass

CBI building in Lodhi Road area, New Delhi

There was commotion at the CBI headquarters in Delhi on the day the Northern Grid tripped in July. Though diesel gensets sprung into action, the building occupants were visibly uncomfortable as the central air-conditioning chillers had no power back-up. The overwhelming glass envelope of the building led to quick increase in temperature. It became unbearable, especially because the glass panels designed as windows would not open. “It was a nightmare,” said an official who did not wish to be named. Frantic calls were made to the National Building Construction Corportion, responsible for its construction, for a solution.

Despite many such experiences, the use of glass in construction is gaining popularity in the country. Industry is hard selling the material on the ground that glass contributes to aesthetics, energy efficiency, safety, security and comfort. Even Saint-Gobain Glass, the world leader in glass manufacturing, has a website glassisgreen.com. The company’s India unit is the founding member of the Indian Green Building Council that awards green ratings to buildings. The website of another glass maker AIS Glass also highlights the green caliber of glass.

Of course, being transparent, glass gives a sense of open space. By letting in natural light, while keeping dust and insects away, it reduces the need for artificial light. But there is a cost to it. Glass traps heat. This is the principle on which greenhouse works. Buildings with high proportion of glass, thus get overheated, pushing up the energy use for keeping it cool. This is unsuitable for the tropical climate of India. “Unlike cold countries, we need to control heat gain,” says Harsha Sridhar, architect with Initiative for Green Habitat in Bengaluru. “In addition we have to deal with the high glare.” Delhi, for example, receives 2,688 hours of sunlight annually as against London that receives only 1,480 hours of sunlight in a year.

“The blinds remain perpetually drawn in our office building despite tinted glass to cut the glare,” says Sahiba Hameed whose office is in a high-rise glass building in Gurgaon. Workstations near the windows become too hot during the day, she adds.

To cut down heat and glare transmission, the glass industry has devised several technologies. A typical version is double glazing with air gap in between for insulation. It is used in most high-rise buildings. An advanced version, triple glazing, is trying to find a foothold in India. But heat transmission through glass is still high compared to other building materials (see infographic). AIS Glass admitted this at a green building rating conference held in Delhi in March 2012.

A study by IIT-Delhi in the national capital city, Jodhpur and Chennai found that energy use increases with the increase in glazed area, irrespective of glass type, climate or orientation of the building. For instance, glazing on the northern wall of a building allows the least gain in heat as compared to any other facade orientation. But if the glass wall covers more than 20 per cent of the south-facing facade, the building overheats even in winters (see ‘Plan your facade’).

image

“There is no doubt that wall-to-window ratio (WWR) is critical in air-conditioned buildings. High amount of glazing leads to higher energy consumption,” says Girja Shankar, assistant energy economist with the Bureau of Energy Efficiency (BEE).

Besides, glass is not an environment-friendly material. It consumes high amount of energy right from its manufacturing to transportation and installation. The embodied energy of glass is between 15.9 and 26.2 megajoules per kg; it is 1.06 MJ/kg for bricks. The embodied energy of glass increases considerably when used as double or triple glazing or when inert gases like argon replace the air gap to further improve performance. “Even the recyclability of glass as claimed by the industry seems dubious,” says Sridhar.

Glass also poses safety concerns. In 2011, Mumbai’s chief fire officer Uday Tatkare told a leading newspaper that buildings with glass facades are major fire hazards and hindrance in fire fighting. Glass sheets often do not have fire retardant coatings and shatter once the threshold temperature exceeds. There are no standards to regulate the quality of glass used in buildings. To make matters worse, BEE offers considerable leeway for the use of glass in commercial buildings. Its energy conservation building code allows a maximum WWR of 60 per cent. “BEE plans to modify this value as different orientations require varying WWR,” says Shankar, admitting that glass structures are not suitable for Indian climate.

Glass is also expensive when compared with other building material. A square metre of glass costs between Rs 1,200 and Rs 7,000, depending on the technology. A good quality brick wall costs less than Rs 1,000 per sq m.

Yet the obsession with glass is growing. “It is even used where it is not required. In buildings like malls, glass facades have become inevitable,” says Haneet Khanna, a Chandigarh-based 3D visualiser. Be it Gurgaon or Bengaluru, instead of innovating designs to suit local conditions, identical glass buildings are being built.

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  • I think that is the reason

    I think that is the reason why the old government buildings constructed earlier in around 1900's maintain good temperature and colder then the new offices which are built using glass.

    Posted by: Anonymous | 7 years ago | Reply
  • Dear Jaspreet That is a very

    Dear Jaspreet

    That is a very accurate observation.
    But nowadays the new government buildings have a high percentage of their facade covered with glass. Some CPWD officials in Delhi claim that they are being pressurized into using large quantities of glass on the façade of new government buildings by senior bureaucrats and officers. These senior officers have seen completely glazed buildings on their visits to foreign countries and want identical if not similar buildings to be replicated in India. It is disheartening to realize that even those who need to set a good example for the public are favoring the design and construction of such structures. Everyone seems to be so overwhelmed by these glass boxes that they do not even consider the impact of our climate on such structures.

    Posted by: Disha Singh | 3 years ago | Reply
  • It is quite surprising why

    It is quite surprising why the windows were jammed.
    How come regular checks and extreme conditions tests were not done in advance. Probable case of Heat thawing.
    In fact building standards should encourage saving on lighting and air management implying more fresh air naturally must be utilized.
    This reiterates the fact and need of low redundancy and improvements on plan C & Plan D as fall backs for A,B

    Posted by: Anonymous | 7 years ago | Reply
  • Hi - Interesting article.

    Hi - Interesting article. Glass boxes in Delhi have been frowned upon for as long as I can remember but they continue to be the norm for new construction specially for commercial buildings. Maybe, it will be interesting to highlight examples of buildings that are built to a similar scale without using all-glass and still allowing for ample daylighting indoors.

    I would also like to know the source of your information on embodied energy for glass and brick that you mention in the article.

    Thanks

    Posted by: Anonymous | 7 years ago | Reply
  • Dear Idikula The problem is

    Dear Idikula
    The problem is that the impact of the Indian climate on buildings with glass facades is ignored most of the time. The issue with the CBI building arose due to the fact that the windows had not been opened before and the workforce within did not know how to operate them. Also as not all the glass panels are openable the window openings were not adequate to ventilate the building,
    I agree with your opinion about appropriate building standards which encourage savings on lighting and natural ventilation. But when such glass boxes are designed in India all passive techniques of controlling thermal conditions in the interior of the building do not work. The bottom line is that glass must be used in a judicious and sensible manner in our buildings.

    Posted by: Disha Singh | 3 years ago | Reply
  • Dear Anjali Thank you for

    Dear Anjali
    Thank you for your comment. I agree that a comparison of completely glazed buildings with those which sensibly use glass would throw light on the suitability of the latter to our weather conditions.

    Regarding the embodied energy values, despite asking various glazing firms for this data no one was able to provide us with the required information. On an average, the embodied energy of a regular glass sheet is said to be 15.9Mj/Kg. But we wanted the data for variants of glass such as toughened glass, tinted glass etc. for which we had to turn to standards of other countries. The values mentioned are from the website of Victoria University of Wellington in New Zealand (Link: http://www.victoria.ac.nz/cbpr/documents/pdfs/ee-coefficients.pdf). One must remember that these values do not include transportation energy, therefore the final values for embodied energy of glass would be far greater especially when they are imported.
    The values for embodied energy of brick have been taken from the following link http://www.docstoc.com/docs/124895631/Energy-in-buildings-BVVReddy

    Posted by: Disha Singh | 3 years ago | Reply
  • Nice insights. The darker

    Nice insights. The darker side of the glaze is a revelation..

    Posted by: Anonymous | 7 years ago | Reply
  • Glass is always synonymous

    Glass is always synonymous with green house effect. This is the reason why old buildings with wooden windows keep cooler than today's buildings with glass windows

    Posted by: Anonymous | 7 years ago | Reply
  • Dear Saurabh Thank you for

    Dear Saurabh
    Thank you for your comment. The endeavour through this article was to stress on the fact that although glazing does have a number of advantages one must look at the negative aspects as well and make an informed decision regarding it's application.

    Posted by: Disha Singh | 3 years ago | Reply
  • Dear Adri You comment

    Dear Adri
    You comment provides an accurate assessment of why glazed buildings do not suit our climate.

    Posted by: Disha Singh | 3 years ago | Reply
  • I would to like know which

    I would to like know which department of IIT Delhi studied this matter. I am also from jodhpur.

    Posted by: Anonymous | 7 years ago | Reply
  • Dear Praveen The mentioned

    Dear Praveen

    The mentioned study was authored by M. C. Singh and S. N. Garg who belong to the Centre of Energy Studies in IIT Delhi. Furthermore, the study is titled 'Suitable Glazing Selection for Glass-Curtain Walls in Tropical Climates of India". Hope this answers your query.

    Posted by: Disha Singh | 3 years ago | Reply
  • Hello, I have been selling

    Hello,

    I have been selling glass for commercial buildings talking about light, thermal/solar heat gain etc.etc..but I completely agree with this article, this material is simply being consumed in higher dosage than required especially on the facade. I would not blame glass as a material but the lack of understanding among consumers. This situation would only get better if we have a system pre-allocation of electricity to buildings before they are built and strict compliance thereafter.

    Posted by: Anonymous | 7 years ago | Reply
  • Dear All It is nice

    Dear All
    It is nice initiative by DTE to make people aware of the situation by using glass as facade of the building. Adding more, the glass facade not only increase the internal temperature it also affect the the micro climate of the area and heat island effect in the locality. I as a green building professional always suggest my client`s to reduce the glass use, at least in southern part of the building.

    Posted by: Anonymous | 7 years ago | Reply
  • Dear All Excellent initiative

    Dear All

    Excellent initiative by DTE and green building is important but not green houses creating heat within and outside building.

    Glass manufacturing itself high power consuming and generates huge amount of green house gases apart from transportation costs which again generates green house gases.
    When supreme court could ban all diesel autos and based on the pollution created by automobiles, but somehow no one has taken up with appropiate authorities surveyed the all glass enclosed buildings in New Delhi and surrounding area.
    Similarly a simple survey how the occupants of theall enclosed glass building felt during power outages and how many did not turn up for work during immediate rectification would have given the effects of glass and its repercussions. And it is only tip of the problem.

    Glass is creating havoc in almost all cities and many cities in south are having the feel of the bad effects and maintain temperature of 27 degrees just to save power and also closes the fresh air and exhaust air systems which increases Carbondioxide level in the rooms and cause health hazards to occupants.
    It is essential it is highlighted in vernacular languages as lot of occupants are from level 2 cities where they normally stay in naturally ventilated areas and are subjected to thermal shock.
    Building services are also designed suiting western standards and the occupants of the building are in alien atmosphere, which creates complications in such buildings.

    Regards Sridhar

    Posted by: Anonymous | 6 years ago | Reply
  • Dear All Excellent initiative

    Dear All

    Excellent initiative by DTE and green building is important but not green houses creating heat within and outside building.

    Glass manufacturing itself high power consuming and generates huge amount of green house gases apart from transportation costs which again generates green house gases.
    When supreme court could ban all diesel autos and based on the pollution created by automobiles, but somehow no one has taken up with appropiate authorities surveyed the all glass enclosed buildings in New Delhi and surrounding area.
    Similarly a simple survey how the occupants of theall enclosed glass building felt during power outages and how many did not turn up for work during immediate rectification would have given the effects of glass and its repercussions. And it is only tip of the problem.

    Glass is creating havoc in almost all cities and many cities in south are having the feel of the bad effects and maintain temperature of 27 degrees just to save power and also closes the fresh air and exhaust air systems which increases Carbondioxide level in the rooms and cause health hazards to occupants.
    It is essential it is highlighted in vernacular languages as lot of occupants are from level 2 cities where they normally stay in naturally ventilated areas and are subjected to thermal shock.
    Building services are also designed suiting western standards and the occupants of the building are in alien atmosphere, which creates complications in such buildings.

    Regards Sridhar

    Posted by: Anonymous | 6 years ago | Reply
  • Would it not help to build a

    Would it not help to build a shallow swimming pool down in the basement simply to draw out the heat, or to have some sort of simple glass water fish tank/s scattered around to act the same way piped into the pool, or to fill the windows with pumped trickling water either inside or out, or to erect some large slanted mirrors columns, or window blinds, these are just a few off the cuff ideas that may have some value, time for tea, will you join me?

    SHERWOOD ENGLAND

    Posted by: Anonymous | 6 years ago | Reply
  • Tinting of double glazed

    Tinting of double glazed glass can be electronically controlled and a simple down load of app can help reduce the amount of heat kept away from the glass
    The installation of these double glazed glass panels can be simple as it is pushed between two channels and then locks it providing secure grip on glass and can withstand upto 1000 km winds per hour pressure.
    US patent was awarded with this unique ability to withstand high winds and shocks created by earth quake

    Posted by: Anonymous | 6 years ago | Reply
  • I am unfortunate not to have come across this article earlier.
    Going by the proliferation of glass façade buildings in the last 5-6 years, either most consultants, architects and developers also are unfortunate like me or are not concerned about our fragile earth.
    It is hard to imagine an educated, construction professional that has come across these facts and shares a concern for the well being of earth to be designing or building a glass façade building in India or any tropical country.

    Posted by: GUEST | 2 years ago | Reply