Living green # 5 GREEN GLASS IS NOT NECESSARILY ‘GREEN’

Since the economic boom in Thailand in the mid 1990s, we have witnessed a major change in contemporary Thai architecture; particularly for high-rise buildings in Bangkok. One of the changes is apparently found in glass-facade corporate buildings. Glass is now used for cladding all exterior walls of high-rise; not only for windows in our homes any more. If we look into the history of glass-facade buildings, we will understand that the idea of using glass facades is originated from the need for daylight and environmental control in cold-climate regions like America and Europe; not for year-round hot-humid climate in countries like Thailand. Something must be really wrong that cold-climate countries like Germany and U.S.A. are exporting more and more glasses to hot-humid countries to build their buildings, whilst the vernacular architecture in these regions are properly designed to protect solar heat as much as possible. Just looking at the traditional Thai houses, both windows and exterior walls are well protected from sunlight in order that the interiors are kept cool. It is considered as an innovative, local intelligence that our ancestors have developed for hundreds of years.

The same intelligence is found in the glass facades used in cold climates. The designers of vernacular architecture in those regions have developed an innovative material that has a superb performance in terms of trapping solar heat to warm the interiors.  Sunlight transmitted through the glass turns into heat and is trapped inside. This is the same effect we are familiar with when we park our cars in the sun. Apparently, it is what we must avoid for hot climates. So, what has given the way for glass façades to come into this country, and who is to be blamed for that? It is the ‘modernization’ that imports architecture from developed countries in cold climates to everywhere on the planet. The term ‘Regionalism’ was almost replaced with ‘Internationalism’ for the country to compete in the globalization arena.

Now, things have already gone too far for us to say ‘no’ to glass façades. So, what we can do is to control the use of glass façades to the optimum by means of building codes. By law, when architects design buildings, they must calculate the amount of heat transfer through envelopes and try not to exceed 45 Watt/sq.m. This has seemed to be a sound measure to save energy in buildings before they are built. Unfortunately, many architects are not well trained to do such a scientific calculation; not to mention about government officials who do not have enough knowledge to check and approve the calculation sheets. This law is now ineffective; leaving us no way to control energy consumptions in new buildings. Then, the modernization goes on and new buildings are consuming more and more ‘make-it-cheap’ energy. There is no doubt why a new glass-façade, high-rise building just appeared in New York is later appeared in Bangkok skyline within a couple of years!!!

Even though, the law has gone, at least it has led us to understand that glass façades are bad for warm climates if we take into considerations of energy and environment. Clear glass is the first thing to avoid for use as glass façades in this climate. Not only does it let in too much solar heat, it also generates glare that the occupants cannot tolerate. This gives a way for tinted glasses, which allow less heat and sunlight. If you look at Bangkok skyline, you will see colorful glass facades; some are blue, some are grey, and some are green.  Possibly, this might be about fashion, but scientifically, it has been tested that green-tinted glass performs better than do the other colored glasses in terms of energy efficiency. That is why many people in construction industry say that green glass is ‘green’ because it saves energy. New housing developments use green glasses instead of clear glasses for windows and claim that the projects are energy saving and then ‘green’. Of course, glass manufacturers produce more green glasses as the public thinks that green glass saves energy.  Sale representatives of housing projects keep telling their customers that their projects are greener than other because of green glasses. Is it that simple?!

Before the public is misled by all advertisements, I must say that green glass is not necessarily ‘green’. Green glass saves energy only when it is compared with clear glass, but having full-height green glass windows (from floor to ceiling) like what in New York will not help you save on energy bills at all. In stead, having a large area of glass is not visually comfortable as too much glare will force you to put on curtains at most of the time. Interior curtains help screen strong sunlight, but the heat already gets inside through the glass. Eventually, no matter what color your glass is, if the windows are not properly designed at the first place to take account on hot-humid climate of Bangkok, you will never really save energy. There are a lot to discuss about using green glass that really save energy, and how a full-height glass façade can be ‘green’.

ผศ.ดร.อรรจน์ เศรษฐบุตร

Asst. Professor Dr. Atch Sreshthaputra

Faculty of Architecture, Chulalongkorn University

Chairman of Green Building Program. The Association of Siamese Architects.

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