A housing shortage in Japan in the 1950s was becoming a big social concern as the people concentrated in large cities. The Japan Housing Corporation was established in 1955, before the existence of large apartment complexes, to tackle the shortage by building urban housing in quantity. Over the next 50 years or so, the corporation was reorganized several times in response to varying demand for housing and ongoing regional developments. In 2004, the Urban Development Corporation merged with the Urban Areas Development Division of the Japan Regional Development Corporation to form the Urban Renaissance Agency (UR). Today, it owns nearly 770,000 rental housing units nationwide (about 1.4 percent of all units in Japan), providing housing for almost 1.7 million people (about 1.3 percent of the population).
Fighting Global Warming through Housing
The average amount of carbon dioxide (CO2), a major cause of global warming, emitted annually per household in Japan is about 5.5 tons. Aware of this, UR decided to employ innovative technologies to improve household energy efficiency, because over 60 percent of household emissions (not including transportation) are to produce the energy needed for air conditioning, water heating, and electrical appliances.
One of the most effective of the various measures employed by UR is the use of improved insulation materials, resulting in more efficient air conditioning and reduced indoor moisture condensation during the winter and general mustiness in rooms. The heat-insulating properties of materials used in newly built housing complexes comply with the next-generation energy saving standards set out in the most recent Law Concerning the Rational Use of Energy. By the end of fiscal 2006, UR had built roughly 10,000 houses under these new standards, resulting in an estimated reduced energy consumption for air conditioning equivalent to a CO2 emissions reduction of about 350 tons per year. Mr. Satoshi Nomura from UR's Urban Environment Planning Office said, "I believe that the heat-insulating properties of our rental housing complexes are the best in Japan."
Another pillar of the measures employed by UR in its rental housing is the introduction of high-efficiency appliances. Resource consumption is reduced by installing latent heat recovery heating and hot water systems, which reuse exhaust heat, and more energy efficient facilities. This measure is applied not only in newly built housing complexes but also in older ones. When old ones are renovated, the appliances are replaced with more energy efficient ones and new heat insulation materials.
"We have continued to improve the environmental quality of our housing over the past 50 years," said Mr. Nomura. "Some residents, for example, had complained that their units were prone to condensation and mold, so we used updated technology and materials to solve these problems, developed jointly with private businesses, while also contributing to efforts to prevent global warming."
UR uses ingenuity and innovative technologies in their housing to further reduce environmental impacts. Some of them were pioneered by the agency, such as a super water-saving toilet system, a residential fuel-cell cogeneration system, a garbage compost system, and a peak alarm cabinet panel that gives an audible warning when electricity is overused.
Buildings Designed and Built for Long Life
UR also addresses the structure of new buildings from an environmental perspective. For example, its new KSI Housing design is built using the skeleton-infill (SI) construction method, in which the structure of the building (skeleton) is separate from the interior and room layout (infill).
The "KSI Housing" design, a UR-version of the skeleton-infill housing method, has a strong frame to increase its durability. The concrete layers around the steel rebar used in posts and beams, for example, are one-centimeter thicker than in standard buildings. This strong frame allows these buildings to last up to 100 years.
In the KSI Housing design, with its floor slab separated from the infill, the partition walls are built after the floor is completed. This makes it easy to move walls or to add new walls even after the entire building has been finished. In addition to the capability of changing room layout, it is also possible to connect two or more adjoining apartment units to make extended larger unit. Such flexibility in design provides the ability to cope with future changes in lifestyles and demand through remodeling, avoiding the need for buildings to be demolished, and thus extending their service life.
Mr. Nomura said, "Construction costs are relatively high, but the KSI housing will be beneficial to residents in the long run because both its lifecycle cost and carbon dioxide emissions will be reduced. Overall, the physical quality of our rental housing is pretty high."
It's also interesting to see how UR rebuilds its aging housing complexes. For example, the demolition of old buildings generates a large amount of concrete debris, estimated to be about 33 cubic meters per unit (two rooms and an eat-in kitchen) in a reinforced concrete building. Since 1992, UR has been recycling waste concrete on-site, whenever possible by crushing it into pieces. The crushed concrete is then used as material for grounds improvement, in the foundations of new buildings, and for roadbeds, depending on the size of the pieces. The rate of recycling concrete debris is now as high as 99 percent.
After many years of use, buildings need to be rebuilt because of a decrease in structural strength due to deterioration of the concrete, and obsolete facilities and equipment that don't comply with improved technical or living standards. Since UR is scheduled to rebuild a large number of housing complexes, its efforts to increase the recycling of construction waste will greatly contribute to saving resources.
Improving the Environment in the Process of Urban Development
UR's housing estates are huge, and such large-scale developments often have substantial impacts on the environment. To avoid this, UR has made every effort possible to minimize changes to the topography of its development sites. Furthermore, it has launched new initiatives that help improve the natural environment of the areas in and around the sites. One of UR's initiatives is to create certain types of natural habitat, or "biotopes."
"In setting up a biotope in our project site, the most difficult thing is keeping the balance between the residential and natural environment," said Ms. Kyoko Ikeda, of UR's Urban Environment Planning Office. For example, as a lot of people don't like insects and worms, too many of them in a biotope may draw complaints. To solve such problems and create consensus on the importance, preservation, and unitization of a biotope before creating it, UR holds study meetings and workshops with experts and residents in housing complexes, local communities, and local non-profit organizations. Such step-by-step communication and planning helps residents see the value of having a biotope. In one local community, for example, a new non-profit organization was established to manage theirs. To create not only housing but also a better residential environment, this initiative is being promoted while encouraging resident participation.
A typical example of UR's rental housing complexes is Sunvarie Sakurazutsumi in Musashino City, Tokyo, which includes about 1,500 units on 44,000 square meters of land. The complex, first built in 1959, was renovated in 1999. There are natural features in the surrounding area that are high in biological value and potential, including Tamagawa Josui, a waterway constructed in 1654 to supply water to Edo, the Sen River, which is about 21 kilometers in length, and Koganei Park of Tokyo with an area of 78 hectares.
As urbanization proceeded in Musashino over time, however, green spaces that provide habitat became separate and scattered about like stepping-stones. To preserve the existing greenery and promote further greening, UR used the renovation of Sunvarie Sakurazutumi as an opportunity and based its planning on the city's basic plan for greenery promotion. Utilizing existing clusters of trees and the Sen River in the residential area helped create a green network.
The riverbed, which had been lined with concrete, was renovated by arranging natural rock and wooden piling to be like a natural river again. Balancing with the natural vegetation of the surrounding area, trees were planted to create a thicket, bushes were added, and a pond was constructed. Creating a biotope in this way is the key to successfully creating a green area with water features, while also providing habitat for many kinds of living things and a place where people can come to relax.
As time goes, the need for new housing arises. In particular, the need to employ an environmental perspective has occurred in many different fields since the Kyoto Protocol was adopted in 1997.
Mr. Nomura said, "We have to have a broader perspective to evaluate how we can consider the environment within limited budgets. In collaboration with the private sector, sometimes differences in demands happen. We must have a thorough dialogue with stakeholders, such as local governments and private-sector housing builders, in order to achieve some common understanding. It is difficult to build 100-percent environmentally friendly housing, but we believe that we may be able to change today's standard specifications in housing by improving as much as we can."
The environmental activities of the Urban Renaissance Agency reflect the present era we live in, while also showing us a valuable direction in designing and building housing for the future.
(Written by Yuko Kishikami)