Japan

Installing Natural Ventilation (NV) system in office buildings leads to the reduction of energy consumption of heating, ventilation and air conditioning (HVAC), which accounts for approximately 50% of total in an office building in Japan. However, it is difficult to estimate the NV performance before its completion, because the NV system is easily affected by the outdoor environment. Thus, its design method is not yet established.

The mainstream of air-conditioning system for medium and small sized buildings is conditionally air mixing ventilation with ceiling cassette unit of packaged air conditioner (PAC), however, it may bring a high cold-draught risk to occupants, due to the direct drop of the supply air jet. To solve this problem, the air mixing ventilation system can be improved into an air based radiant air-conditioning system by stretching the non-flammable membrane under the ceiling with PAC, thus the cold-draught of PAC could be substantially eliminated and the indoor environment could be improved easily.

Recently in Japan, many buildings introduce packaged air-conditioner (hereinafter, this is called “PAC”) as an air conditioning equipment. Most of the PACs can change the direction of supply air blown from the unit and the “Swinging Mode” can change airflow direction periodically as one of the airflow direction setting of PAC. Before constructing the building, appropriately predicting the indoor environment (e.g. temperature distribution or air velocity distribution and so on) is important for indoor environment design.

The ventilative cooling by natural ventilation is important technology for the buildings in urban area for the sake of energy saving and BCP (Business Continuity Plan). In fact, a large number of high-rise buildings in urban area in Japanese metropolises are equipped with natural ventilation apparatus such as openings and chimneys or shafts.

In recent years, not only the residence but also the effort of health promotion by improving the social environment including the working and the regional environment has attracted attention. Because of the significant amount of time that office workers spend in the workplace, ideal modification of their working environment and work habits could potentially improve both their intellectual productivity and their physical health. However, optimal environmental improvements have not yet been identified. Therefore, in the present study, we developed a revised version of CASBEE-OHC.

A “heat recovery hybrid ventilation system” is the combination of passive stack ventilation and mechanical push-pull ventilation. Two heat storage boxes are connected to the natural EA stack and the underfloor natural OA duct. The alternation is done periodically in a way of that the outdoor air is drawn through one of 2 boxes contains earth tiles and the indoor air is exhausted through the other box.