Evaluation of energy conservation for cooling through natural ventilation in Japan

In summer, most areas in Japan are hot and humid. Hokkaido Island, which is the most northern part of Japan, is the only exception. However, air conditioning systems have become the norm in all big buildings in Japan, even in Hokkaido, due to increased internal generation of heat from lights and equipment such as computers and printers. However, the outside air temperature often drops below 26C during summer everywhere in Japan even when cooling and air conditioning is turned on. Buildings are closed to the atmosphere and only the needed volume of outside fresh air is introduced into the building by mechanical ventilation.
In countries such as Japan where buildings have large cooling loads, this concept can be interpreted as a combination of natural ventilation and mechanical cooling. In other words, such a system aims to reduce mechanical cooling energy consumption by introduction of natural ventilation. Some big buildings in Japan have already adopted ventilation systems that combine natural and mechanical ventilation. But, no integrated study has been done into the potential of natural cooling and reduction of energy consumption for cooling by introducing natural ventilation for Japan as a whole. Therefore, the authors evaluated quantitatively the cooling capacity of outside air and reduction of cooling load that could be achieved if typical commercial buildings were to introduce natural ventilation systems, for different locations in Japan. In total we performed calculations for 842 locations in all parts of Japan by using the expanded AMeDAS Weather Data, which is supplied from the Architectural Institute of Japan (AIJ). These calculated results are visually shown by colored contour maps.