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NatureInterface > No.01 > P028-031 [Japanese]

Environment and Residence: The Greenhouse Effect in Glazed Buildings -- KyoFuyusawa

図の英語訳はありません

Environment and Residence

The Hothouse Effect in Glazed Buildings

Modern structures are made of industrial steel and glass. Here we take a look at the history of glazed buildings and their impact on the environment.

Kyo FUYUSAWA

The growing numbers of glazed buildings

Since 1974, when the Shinjuku Mitsui building was erected in Japan, the number of glazed buildings has rapidly increased. Many glazed buildings now feature even central open areas called atriums. Traditionally, of course, an atrium was a front garden, but today people often apply this term to the courtyard-like, glass-ceilinged space inside large structures such as hotels and office towers.

Why did glazed structures become so popular? Several factors--the manufacture of large panes of glass, the development of large central air-conditioning systems and the design trends of post-modern architecture--combined to make these buildings popular.

In cold climates, such as northern Europe and Canada, large numbers of glazed commercial facilities have been built. The largest of these is the West Edmonton Mall in Edmonton, Alberta, Canada. This structure is called "the torrid zone for the extreme north," and it includes a big shopping center, including a leisure center with a central heated swimming pool. The same facilities were planned in Japan during the bubble boom, but only Sea Gaia, in Miyazaki Prefecture in southern Japan, somehow managed to be built.

Many glazed buildings are office towers rather than shopping malls or other commercial facilities. Wherever you go around the world, such towers scrape the skies from northern cities such as New York and Toronto to southern cities such as Miami, Bangkok, Hong Kong and Dubai.

Several years ago one Christmas Eve, I got stuck in one of Bangkok's infamous traffic jams. I found myself looking at a post-modern mirror-glazed building, which displayed the outdoor temperature: 37℃. I had to wonder why buildings like that are built in climates that, like Thailand's, are already hothouses.

Is a glazed building hot?

I can understand the purpose of glazed buildings in cold regions such as northern Europe. But I expected that if you put the same buildings in the tropics, they would be quite hot. Because I couldn't simply fly to the tropics to satisfy my hunch, I investigated glazed buildings in Japan, where summer brings the conditions of a torrid zone. The first building I studied looks about like an egg when viewed from above. Its walls are glass, and its roof is the only thing different from a hothouse. The photograph shows the south side, where there is an airy atrium through three floors. There is no air-conditioning system on this side.

I measured the air temperature inside the atrium on a day at the end of July. As the sun rises, the indoor temperature also rises and the east-side windows receive direct sunrays. By 8 a.m., the outside temperature is 40 ℃ and the room temperature reaches 28 ℃; the air conditioning now starts up. From about noon to 4 p.m., the atrium temperature rises past 35 ℃, the same as in a hothouse. Towards evening, without the direct rays, the temperature begins falling, but the atrium retains its heat because it takes time to release its warmth into the walls and floors. After 10 p.m., the atrium's temperature finally falls to 30 ℃.

Thus, I knew that a glazed building can indeed get hot. And the air-conditioning system needed to deal with the heat is extremely expensive.

The building I investigated is made of transparent, single-pane windows, the worst material for an office building--in fact, the ideal material for a greenhouse--. But ordinary office buildings are made of colored glass that absorbs thermal rays, or else mirror glass that reflects light and thereby limits solar radiation entering the building. Actually, in hot regions, lots of buildings have been made of colored-mirror glass. At the same time, in cold areas such as northern Europe, most buildings use transparent glass in order to help heat the buildings during cold weather.

In many commercial structures where large numbers of computers are in use, air conditioning is needed even in the winter, because of the heat produced by the computers and other office machines. In this case, absorption of external energy should be minimized, so a hothouse is not suitable for them.

Mirrored glass also limits entry of the sun's rays into the building, but reflected rays often make other problems. In Bangkok, an elementary school's people filed a lawsuit against the owners of a new mirrored building because the sun's reflection had been making the school hot. Some people say when they walk among mirrored buildings of Tokyo, they feel like they're in an oven.

Mirrored buildings have modern beauty, and their popularity in tropical cities has increased along with the popularity of post-modern architecture. However, they also seem to have environmental problems. It seems that we need to select an architectural style that corresponds to the climate and natural features of a region.

Fig. Caption

The large greenhouse in The New York Botanical Garden, Bronx, New York, was built in 1899. On the day I visited there, the temperature outside was below the freezing point but inside was so warm that I felt as if I were in a world apart.

A building where a hothouse is used for dwelling in (Kanagawa Prefecture).

A glass building in New York with dazzling reflection of sunlight.

An institute of a university.

A glass building in Bangkok, Thailand. Glass buildings came to be found even in tropical areas these days.

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