Pursuit of "energy saving" and "comfort"

Key areas for energy reduction include facade, air conditioning, and lighting. Regarding facade, remarkable improvements have been seen in their performance in recent years. While double-glazed windows were once only used in openings in cold regions, high-performance low-E double-glazed windows are now standard in many buildings. Compared to single-pane glass, they offer approximately three to four times the thermal transmittance and approximately twice the heat-blocking performance. Since glass typically accounts for 40 to 60 percent of the exterior wall area of an office building, the effect of reducing solar load can be considered significant. Furthermore, efforts are underway to achieve both solar shading and daylight utilization, such as the adoption of light shelves and blinds with automatically controlled blade angles. Furthermore, windows that can be opened and closed for ventilation are being reconsidered, and the installation of openings with natural ventilation functions is also increasing.

In Germany, which is said to be an environmentally advanced country, lighting, especially natural light that penetrates into the interior of a building and natural ventilation, are considered important in creating a "comfortable work environment." Commerzbank, a skyscraper office building in Frankfurt designed by Norman Foster, is known as a sustainable building. The atrium, located in the center of the triangular plan, is designed so that the light and air entering from the outside are drawn into the offices from this atrium. The offices are deep enough to allow effective natural light to reach them, and during the daytime the lighting environment is usually based on this natural light and task lighting.

Another thing to note about this building is the air conditioning. In recent years, "radiant air conditioning" has been spreading in Europe, mainly in Germany and Switzerland. The big difference from other air conditioning methods is that it does not use cold or hot air, but circulates cold and hot water through radiant panels installed on the ceiling, and uses the property of heat moving from high to low temperatures, "radiation." The biggest feature is that there is no air current, there is no blowing noise, so it is quiet, and the temperature inside the room is uniform. From the perspective of "comfort" in the office environment, it can be said to be an extremely excellent air conditioning method. Also, from the perspective of "energy saving and CO2 reduction," it is excellent in that it uses "water" to transfer "heat," which is more efficient than "air," and because the temperature of the cold water used is relatively higher than that of air conditioning methods, it requires less energy to produce cold water. In addition, free cooling can be used to utilize cold water in winter and mid-season, which further saves energy. In Japan, humidity control requires ingenuity, such as the use of desiccant outdoor air conditioners, but this "radiant air conditioning" is beginning to attract attention as an air conditioning method for office buildings.

In the lighting field, awareness of energy conservation has increased since the Great East Japan Earthquake, and the transition to LED lighting is progressing. At the same time, the price of LED lighting equipment has fallen, and the switch to LED lighting is progressing not only in new buildings but also in existing buildings. In addition, the lighting environment in offices, which previously had an illuminance of 700lx to 1000lx using general lighting methods, can now be set to the appropriate illuminance by using sensors and automatically adjust the light according to changes in brightness on the window side, resulting in significant energy savings. When task/ambient lighting is adopted (ambient 300lx, task 700lx), it is possible to reduce energy consumption by 40% to 50% compared to general lighting methods. In addition, methods have become more diverse, such as being able to freely change illuminance and color temperature, and the creation of lighting environments that are not only "energy saving" but also "comfortable" has begun.

As mentioned above, it is possible to simultaneously pursue "energy saving and CO2 reduction" and "comfort" in the thermal and lighting environment of an office building. For office workers, the office is where they spend one-third of their day. Although the requirements differ depending on the type of work and occupation, we would like to further promote efforts to create a "comfortable working environment."