What kind of mattress is suitable for the Japanese climate?

Japan is long from north to south, and the climate and temperature and humidity vary greatly depending on the region and the seasons. What kind of mattress (bedding) is suitable for Japan?

1. The first mattress (bedding) used in Japan.

If you look into the history of Japanese mattresses, they are much older than you might think, and they are said to have been used by Emperor Shomu more than 1,200 years ago. The bed called ``Gosho'' (ontoko) is made of cypress with a slatted structure. It seems that on top of that was a tatami with a black brocade border and a brown brocade bedcloth. Furthermore, I have heard that traces of beds have been found in the ruins of dwellings dating back to the early Kofun period, so if that's the case, the history of bedding may date back 1,600 years.

The tatami in the old days refers to a mattress, not the tatami of today. The shape is similar to that of a katakana (rata) layered on top of each other and bound with thread. Materials include Igusa and Makomo. A tatami mat with many layers of straw mats is called a ``yae tatami''. It seems that some were made with layers of animal skin. Since ancient times, humans have always sought a comfortable bed.

2. Conditions for a mattress (bedding) suitable for Japan.

Currently, the mainstream mattress structure is a steel wire spring invented in the 1920s, with padding such as urethane or felt on the top and bottom, and covered with a cloth cover. In recent years, there has been an increase in the number of springless materials such as urethane alone and latex made from foamed natural rubber.

In Japan, where the environment changes significantly with the four seasons, the climatic conditions of sleeping places are an issue. Thread bedding and bedclothes used when sleeping. This creates a small space around your body that is isolated from the bedroom environment. The air condition in this space is called the sleeping climate. Temperature and humidity have a strong influence on the comfort level of the sleeping climate. The human body enters the gap between the throw bedding and the mattress, which generates heat and releases moisture. Therefore, the climate inside the bed is different from the room and outside air.

Is there a seasonal change in the climate inside the sleeping area? Generally, the temperature inside a bed does not change much throughout the season, as it is regulated using comforters and other means. On the other hand, there are large fluctuations in humidity. This is especially noticeable in the summer.

According to previous research, the relative humidity in the area where the mattress and back touch can exceed 90 % during the summer. The ideal humidity is around 50± 5%, but there is a wide difference compared to that. The amount of sweat you sweat during sleep is usually about one cup per night. In summer, when temperatures are high, the amount increases more than usual. Sweat increases the humidity on your back, leading to an uncomfortable stuffy feeling. You often turn over in bed to ventilate the warm moisture on your back, making it difficult to get a deep sleep. The secret to a good night's sleep in summer is to suppress the moisture on your back. A mattress (bedding) made of highly moisture-controlling material will keep your back feeling refreshed and reduce unnecessary tossing and turning.

Related article: How to choose bedding and mattresses: Two basics.

When it comes to mattresses, the key is sleeping posture and turning over.