Utilizing Wind in Sustainable Design

In this issue we continue publishing chapters from the book “Sustainable Architecture in Japan: The Continuing Challenge 1900–2010 & Beyond”, published to coincide with the 110-year-old anniversary of Nikken Sekkei. In previous issues (Green Buildings, № 2–3, 2013) we reported on the use of natural light and heat in architecture. Now we will focus on wind – on how applying modern design techniques a building can do without air-conditioning systems.

Merits and Drawbacks of Wind
Wind results from pressure differentials. Since solar heat creates pressure differentials, wind is, in a sense, a type of natural energy. However, wind is not always advantageous: throughout the ages, people have erected buildings to shelter themselves from typhoons, gusts, tornados, and other similar forces of nature. When designing buildings designers must be mindful of both the productive and deleterious effects of wind.

The Effects of Natural Ventilation
There are many advantages to effectively utilizing wind. In recent years, buildings that actively utilize natural ventilation have received much attention. In Japan, year-round air conditioning systems, which came into use in the 1960s, created buildings whose indoor temperatures were consistent throughout the year. When air conditioning is used continuously, the easiest means of controlling the indoor environments is to install fixed windows. If this yields comfortable indoor environments, people who live and work in the buildings tend to ignore outdoor climatic conditions and tend to wear the same clothing year round, regardless of the season.

Gail Brager of the University of California, Berkeley and Richard de Dear of the University of Sydney conducted extensive studies of naturally ventilated and mechanically air-conditioned buildings and created the “adaptive comfort model” based on their findings. Their studies revealed that the occupants of naturally ventilated buildings were more likely to find warm indoor temperatures comfortable when it was warm outside and cool indoor temperatures comfortable when it was cool outside compared to occupants of centrally air-conditioned buildings. From this finding, we can deduce that people feel more comfortable in buildings that maintain a connection with nature.

Utilizing natural ventilation in buildings requires either temperature differentials or wind pressure. In factories and other large spaces, one can effectively utilize winds resulting from pressure differentials to induce natural ventilation. To achieve similar results in office buildings, however, one must install double skin facades or balanced ventilation windows, or must devise other comparable methods. Openable windows must be fully air-tight when closed, however, or they will cause unwanted drafts.

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Materials provided by Nikken Sekkei
Text: Shin-ichi Tanabe