Japan

Japan is characterized by high humidity in summer and low humidity in winter. Therefore, summer is in a climatic condition where mold is easy to grow, and in fact, mold damage is occurring. Due to improvement of the thermal insulation and airtightness of houses, the temperature in the room is maintained high even in winter, and mold damage occurs. We will introduce the research we have conducted regarding humidity environment and health problems, and discuss future subjects. The outline is as follows. 

People spend 70% -90% of their time indoors. Indoor air quality and human body’s health have a close relationship. With the advance of society, user comfort requirements for thermal environment are rising. Humidity is an important parameter for evaluating indoor air quality, which not only affects the thermal comfort of the human body but also seriously restricts the function of the building. In winter, the indoor humidity is dry. When using humidifier, the humidity around the humidifier is higher, but there is still a dry area in the room.

In recent years, many multi-type package air conditioning systems for buildings have become widespread in office buildings in Japan, and there are many cases where one air conditioning space is shared by using several indoor air conditioning units. The advantages of multi-type package air conditioning system are that it is possible to operate and control individually for each indoor unit, and that the user can arbitrarily change the temperature setting of the indoor unit.

Japan will have to further reduce CO2 emissions to meet its obligations under the Paris Agreement negotiated at the 2015 United Nations Climate Change Conference. Society is increasingly demanding higher energy-efficiency standards and zero-energy buildings because general commercial buildings have high energy costs, especially for air conditioning.

Building dampness and mouldy indoor environments are associated with the increase of approximately 30-50% in variety of respiratory and asthma-related health outcomes through a meta-analysis. The indoor environment related to indoor dampness is not be revealed yet, however it is important to provide the architectural techniques and optimal occupant behavior for prevention of dampness in buildings. The authors previously proposed an estimation method for home dampness using occupants self-reported answers to questions about visible vapor condensation, visible mould growth during winter.

Allergic symptoms are closely related to indoor allergens, such as airborne particulate matter, fungi, and house dust mite. This paper introduces a central air-conditioning system integrated with an electrical dust collector developed as a countermeasure against allergy. Here, it was demonstrated that this air-cleaning system can remove fine particles of PM2.5. Objectively, this study aims to elucidate the relationship between indoor allergens and occupants’ allergic symptoms.

There is no doubt that odor is also an important factor to evaluate indoor air quality. Since the olfactory system was proven to be closely related to the limbic structures which support emotion, long-term memory and motivation, the psychological and the physiological effects of the essential oils have been widely researched in various fields. The odor environment formed by essential oils is popularly used in commercial facilities to make customers have special mood.

In recent years, especially, the climate change (CC) and urban heat island (UHI) effects are becoming serious problems, affecting people’s life and health, especially in hot summer. For large cities such as Tokyo or Osaka in Japan, the UHI effect is particularly intense. It is known that about 40% of urban anthropogenic heat comes from buildings in large cities. To reduce the anthropogenic heat from buildings is an important countermeasure to this problem.  

The perimeter space near windows usually has some problems with the thermal environment which is easily affected by heat transfer and radiation from windows. Compared to interior space of the room, the airflow in this area usually has different characteristics due to the effect of buoyancy, thus it may reduce thermal comfort of perimeter space. To improve the thermal environment in perimeters, breeze line diffusers are widely used in Japan as the terminal equipment of air conditioning and ventilation systems. This diffuser is the same as so-called ceiling slot diffuser.