NATIONAL SCIENCE FOUNDATION
TOKYO REGIONAL OFFICE

The National Science Foundation's (NSF) Tokyo Regional Office periodically receives and disseminates reports on research developments in Japan that are related to the Foundation's mission. It also provide occasional reports on developments in other East Asian Countries (http://www.twics.com/~nsfasia/as-reports.htm).

These reports present information for the use of NSF program officers and policy makers; they are not statements of NSF policy..

Special Scientific Report #01-08 (December 4, 2001)

The following report was prepared by Mr. Joseph DiDio, a graduate student in the Engineering Research Center at Columbia University. Mr. DiDio was a participant in the 2001 Summer Institute Program in Japan, co-sponsored by the National Science Foundation and the Japanese Ministry of Education and Science (Monbukagakusho). He conducted his research under the direction of Dr. Takao Sawachi of the Building Research Institute in Tsukuba, and can be reached at jd397@columbia.edu.

While it has always been recognized that the buildings in which we live and work have a profound influence on our lives, their impact on the environment has been less obvious, but no less significant. A substantial percentage of the total amount of energy consumed in the United States goes into heating and cooling of buildings, making that sector an important source of emissions such as carbon dioxide. By increasing the efficiency of buildings, large amounts of energy and therefore money can be saved, and the emission of a significant amount of pollution can be prevented. Furthermore, the more efficient use of energy can lead directly to a decreased reliance on foreign sources of fossil fuels, and make a nation less susceptible to price spikes and shortages caused by political or economic problems in oil-producing regions of the world.

Though the United States has substantial fossil energy resources, Japan has a far smaller domestic supply, and is forced to make up the difference with a proportionally larger amount of imported fossil fuels. Research into ways to increase energy efficiency in Japanese homes has, and can continue to significantly reduce the amount of energy that is required to satiate the heating and cooling demands of a modern nation.

The Kanto region of Japan has hot, humid summers and cold to mild winters. These climactic conditions suggest that cooling requirements predominate over heating requirements, so the most benefit from energy efficiency lies in reducing the cooling demand without sacrificing comfort or standard of living. One idea to accomplish this is to design buildings such that they capture the natural prevailing winds and channel them through occupied rooms during the warmer periods of the spring and fall seasons, thereby minimizing the need for air conditioning. Air conditioning would still be necessary for the hottest and most humid days of summer, but the cumulative yearly demand would be greatly reduced.

Traditional architecture has utilized climactic design for thousands of years to help moderate comfort levels within buildings, but it appears that the precise analysis of the effect of cross-ventilation on temperature throughout a building under natural conditions has never been undertaken before. It involves continuous measurements of temperature, humidity, wind speed and direction at many spatial coordinates in each room of a sample building, along with simultaneous data of outdoor climatological conditions. It is hoped that research into this phenomenon will allow for reasonably accurate predictions of temperature and air circulation performance, based on local climactic conditions, and allow for optimization of air inlets and outlets to achieve comfortable, reliable and less energy intensive cooling for Japanese homes.

A model 2-story home situated on the campus of the Building Research Institute (Kenchiku Kenkyujyo) in Tsukuba-shi, Ibaraki-ken served as the experimental test site. Thermocouples were constructed and connected in clusters of five to take measurements at five heights within each room simultaneously. Each of these sensor clusters was installed in rooms of the house according to a grid pattern with each cluster spaced approximately 100 centimeters apart. Anemometers were placed on the floor and at 1m heights at these same locations, in addition to a single hygrometer for each room. The thermocouples were connected to a central control board and desktop computer, which also collected data from wind velocity and temperature sensors mounted on an adjacent structure. The initial experiments were conducted over a number of days with various combinations of open and closed windows in the second story rooms, for the purpose of refining and optimizing the experimental setup for experiments that were to begin in September 2001. Thus, the data collected during July-August 2001 is relatively primitive and constitutes the first generation observations of cross-ventilation and its effect on temperature. The preliminary data will contribute to a better understanding of this relationship, and could lead to a methodology for precisely predicting it, which has thus far not yet been achieved.

Processed data from one particular experimental setup is displayed in Figures 1 and 2, which show the outdoor wind speed and direction and its effect on room temperature, respectively. In this particular setup, it was observed that with two open windows, room temperature drops uniformly, but with one open window, the temperature decrease occurs as a function of height. Further experimentation will be undertaken to flesh out and quantify this phenomenon with the eventual goal of utilizing it in future building codes and standards. It may be possible to develop a standard method to fine-tune natural ventilation in order to reliably cool the zone where the occupants are, without having to cool the entire room.

This series of experiments is guided by Dr. Takao Sawachi, Chief Researcher in the Environmental Engineering group and by Mr. Masaki Tajima and Mr. Hironao Seto, senior researchers. Data collection and processing has been done by students Mr. Shinya Tazawa, Mr. Shouichi Hukuyo and me.

In addition to access to the testing facilities at the Building Research Institute, the Summer Institute in Japan program provided the opportunity to visit and interact with several Japanese scientists in research institutions all over the country whose research interests coincide with my own. Visits were made to Dr. Tomonari Yashiro of the University of Tokyo, Dr. Akashi Mochida at Tohoku University (Sendai), Dr. Akira Fukushima at the Hokkaido Prefectural Cold Region Housing and Urban Research Institute (Sapporo), and Dr. Atsushi Inaba at the Research Center for Life Cycle Assessment, AIST (Tsukuba). These visits were truly interesting and provided a fascinating insight into the Japanese research community.

The time spent in Japan has not only been a terrific personal and professional experience but has opened the door to possible future collaborations with researchers encountered on professional visits as well as with my host. My doctoral research involves scrutinizing a facility with a tremendous cooling demand. Insights gained from the work of Japanese scientists regarding building modeling and design, energy consumption and the interactions between buildings and the environment will be of direct benefit to my research. The 2001 Summer Institute in Japan program was an amazing experience, and I am very grateful to have been given this opportunity.

　Figure 1

Figure 2

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