icrn phw energy cse dte gobar times rwh csestore iep aaeti
Features

Reflections on glass

18 Comments
Author(s): Disha Singh
Dec 15, 2012 | From the print edition

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

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.

AddThis

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.

30 November 2012
Posted by
Jaspreet Bajwa

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.

1 December 2012


Posted by
Disha Singh

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

10 December 2012
Posted by
Idikula Mathew

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.

12 December 2012


Posted by
Disha Singh

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

10 December 2012
Posted by
Anjali Mangalgiri

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

12 December 2012


Posted by
Disha Singh

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

14 December 2012
Posted by
saurabh

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.

17 December 2012


Posted by
Disha Singh

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

15 December 2012
Posted by
Adri S Basak

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

17 December 2012


Posted by
Disha Singh

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

9 April 2013
Posted by
praveen

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.

9 April 2013


Posted by
Disha Singh

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.

22 May 2013
Posted by
lakshman

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.

16 July 2013
Posted by
BHUWAN BHASKAR

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

19 September 2013
Posted by
Anonymous

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

19 September 2013
Posted by
Anonymous

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

11 January 2014
Posted by
Robert Sherwood

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

10 April 2014
Posted by
Arshad Kazmi

Post new comment

The content of this field is kept private and will not be shown publicly.
CAPTCHA
This question is for testing whether you are a human visitor and to prevent automated spam submissions.


(Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.)
CSE WEBNET
Follow us ON
Follow grebbo on Twitter    Google Plus  DTE Youtube  rss