This section provides details and results regarding specific environmental initiatives ranging from environmental protection at construction sites to environmental technology and businesses.
In recent years, urban heat island effects, frequent sudden torrential downpours, and other unusual phenomena have come to seriously affect community life. Taisei is striving to mitigate these environmental changes and take measures regarding them though the application of a wide range of technologies.
The Urban Net Nagoya Building, constructed by Taisei, is a large, 22-story high-rise building with three underground stories and which has a total floor area of 76,467 m2, 1.6 times as large as Tokyo Dome. This building fronts a broad street on its northern and western sides and stands adjacent to residential areas and shops on its southern and eastern sides. Since this is a large construction project which was carried out in a demanding environment, preserving the surrounding environment in addition to ensuring zero emissions* through comprehensive recycling and the separation of waste was a major issue to be addressed.
In this project, Taisei installed Kinrinkun, a giraffe-shaped system that measures and displays vibration and noise levels, in order to disclose information on these levels so that residents in the neighborhood and general passers-by could look at the measured values at any time. In addition, 0.9-meter-high sound-absorbing panels were installed on top of 3-meter-high flat panels covering the construction site to prevent noise from affecting the neighborhood.
Besides these measures, Taisei put its energies into promoting better communication with people living in the neighborhood. Examples included installing bulletin boards so that residents’ associations in the neighborhood could use them freely, cleaning areas surrounding the construction site, planting seasonal flowers in pots installed around temporary hoarding, and displaying pictures painted by elementary school students in the neighborhood.
* Zero emissions refer to activities aimed at reducing the discharge of waste that cannot be recycled to zero.
Urban Net Nagoya Building under construction
Children’s works displayed on temporary hoardings
As the temperature continues to rise in cities due to heat island effects, trees lining streets in urban districts play an important role in preventing heatstroke in the city mainly by providing shade for sidewalks and curbing rises in temperature. Roadside trees, on the other hand, bring negative effects such as lower wind velocity due to the resistance of their crowns and higher humidity due to transpiration. It is believed, therefore, that effective roadside tree plans can be worked out if these advantages and disadvantages are taken into consideration in advance. Taisei has used T-Heats District, a three-dimensional heat-island analysis and assessment system that takes into account insolation, radiation, air currents, temperatures and humidity levels, to identify the optimal size of roadside trees and their optimal intervals. An effective arrangement of trees along a street makes pedestrians feel, on average, two degrees or more cooler on its sidewalk.
A comparison of sensible temperatures under roadside trees under the three-dimensional heat-island analysis and assessment system
Rooftop greening has become the subject of public attention as a measure to deal with heat island effects, but it is thought that the maintenance of this, which is troublesome, prevents it from being widely used. Taisei has developed lightweight soil using aggregate produced from used polystyrene foam (Tepsa). The company combined this soil with rock fibers, which serve as an aquifer, to create a rooftop greening system, which enables users to reduce the need for water sprinkling in summer to half of the previous level. Use of this system in combination with Misato, a variety of Japanese lawn-grass, allows users to maintain their lawns by mowing it only two or three times a year. This soil makes rooftop greening maintenance-free with its benefit not just limited to reducing the need for water sprinkling. In addition, since lightweight soil is used, it is possible to reduce load on existing buildings when implementing greening plans.
Cross-sectional view of the structure of the greening system, which enables users to maintain their green spaces by watering only twice a week even in summer (ten liters of water per square meter each time), which helps reduce the heat load for buildings.
Not only can heat island effects be reduced, but also spaces for recreation and relaxation can be provided to people living in the city by promoting rooftop greening.
Slope greening using inclined roofs
In the Shimokitazawa Seitoku High School (Setagaya City, Tokyo) project, was completed in February 2005, trees were planted on the entire surface of the gently curved roof, which descends in a slanting direction from the top of the existing school building to the ground, to provide this urban school with a landscape robed in greenery. This slope greening not only improves the scenery which can be seen from the windows of the school building and brings an emotional healing effect to the school personnel and students but also contributes to reductions in environmental impact, such as the controlled reflection of sunlight coming through the windows. This facility received the Wall Surface & Special Greening Grand Prize from the Minister of the Environment in the Fifth Rooftop, Wall Surface, and Special Greening Technology Competition.
The Sapporo Prince Hotel project involved demolishing the hotel’s three-story concrete banquet-room section, which was connected to the twelve-story accommodation wing, and constructing a new, 25-story tower at the site. When demolishing the banquet-room section and constructing the new tower, Taisei was required to reduce the volume of noise, vibrations, and dust generated as much as possible so that such nuisances did not affect not only users of the hotel, which was in operation, but also the occupants of apartment houses, students at preparatory schools, and other persons concerned in the neighborhood.
As a solution to this problem, Taisei determined that separating the banquet-room section from the accommodation wing before the former was demolished would be effective, and applied the edge cutting method, which uses wire saws. It was believed that it would be difficult to apply this method to a large building cross-section (335 m2 in this project), but the separation work progressed smoothly, and Taisei completed the demolition work without receiving any complaints even from hotel users, who might otherwise have been affected the most, during the entire project.
Edge cutting method using wire saws
External view of the demolished building
In order to not only take measures to cope with heat island effects but also contribute to reductions in CO2 emissions through energy conservation, Taisei has developed Tepsa-based Cool Wall, which is installed on the external walls of buildings. Employing aggregate produced using used polystyrene foam as a material (Tepsa), this is a wall panel that is light and has a high level of water retentivity.
Water is supplied directly into the interior of the wall through suction tubes buried in panel joints. Through the heat of evaporation, the temperature on the wall surface is reduced, and the intensely hot environment around the walls is also mitigated. The maximum heat reduction effect is about 12 degrees.
It is also possible to establish a more environmentally friendly system by using photovoltaic power generation as a power source for the feed pump.
Figure showing the outline of a system that uses Tepsa-based Cool Wall, which contributes to further reductions in CO2 emissions through utilization of rainwater and photovoltaic power generation
Thermographic images comparing temperatures before and after the Tepsa-based Cool Wall is installed. The Cool Wall lowers the temperature on its surface, mitigating the intense heat around the wall.
Tepsa-based Cool Block used at the eastern terminal of the Expo 2005 Aichi Japan’s Nagakute site
Taisei provided the Expo 2005 Aichi Japan site with a water-retentive pavement system equipped with a water supply device, which was effective in dealing with heat island effects during the height of summer.
This system involves paving a road with light, water-retentive blocks as a measure to deal with the heat from the paved road in high summer and lowering the temperature on the road by dissipating heat through the evaporation of water. During the daytime in summer, the temperature on the surface of the road can be reduced by around 15 degrees.
Materials obtained by recycling used polystyrene foam are used for the water-retentive blocks, and the automatic supply of rainwater stored in the tank through photovoltaic power generation plays a role in preventing global warming.
Compared to the previous forecasts, the radar analysis of precipitation enables prediction of localized torrential downpours.
In recent years, localized violent downpours have frequently caused floods in various places in Japan, and the scale of damage caused by these floods has expanded each year. Against this backdrop, the development of a system to analyze and predict the flow of rivers accurately as a tool to support flood risk management and measures to reduce flood damage was much in demand. Since localized torrential downpours occur in small areas several kilometers square, it had been believed that it was difficult to predict such downpours using conventional analysis systems based on rain gauges installed at intervals of up to 20 km. Taisei’s recently developed river outflow analysis system for response to localized torrential downpours integrates precipitation data analyzed by high-resolution radar units installed at intervals of 1.0 km with geographical and land use data obtained at fifty-meter intervals (numerical information on national land) for analysis. By doing this, the new system can provide more accurate analyses of floods for all types of rainfall.
This system is under operation in some civil engineering worksites.
Taisei’s simulation technology provides a means of visualizing wind energy, which is greatly affected by the surrounding environment, and enables us to make detailed assessments of projects and usage plans.
The most efficient measure for reducing CO2 emissions is the use of recyclable natural energy (such as wind, solar and heat). Of these natural resources, wind energy is characterized by its short-term local instability and is also susceptible to the effects of the surrounding geography and obstacles.
Taisei’s environmental simulation technology makes it possible to “visualize” these invisible natural energy sources in order to make effective use of them. The project for a wind power station constructed in Tahara, Aichi Prefecture, whose management Taisei participates in, was conceived and planned using the Wind Power Generation Prediction and Assessment Technology, one of the fruits of our technological development.