In Japan’s climate, even remodeling, if not properly treated for humidity, will cause buildings to rot and harm the health of the inhabitants.
If the humidity remains stagnant, molds, mites and wood-rotting fungi will grow and give Japanese termites a place to play an active role.
Since Japan is a country with a lot of rain and high humidity, it is necessary to think carefully about measures against humidity.
The troublesome part of humidity damages both the building and the people who live in it, and it is not enough if it is only dry.
“Not so high and not so low” is required.
It is a country that needs a dehumidifier in the summer and a humidifier in the winter. So the building is difficult. It is necessary to maintain an appropriate humidity balance throughout the year.
From the perspective of the building, in order to keep the building healthy and long-lived without rotting, it includes not only the interior space but also the so-called skeleton space that surrounds the room, such as the space under the floor, inside the walls, and the hut space. You have to protect it from the harm of moisture.
Recently, there is a method of mechanically ventilating the room and the space inside the body all year round and adjusting the temperature. It is a highly airtight and highly insulated house with 24-hour mechanical ventilation, and you do not have to open the windows all year round.
This would belong to the category of how machines should be used rather than how buildings should be made.
Buildings are where people live for decades, so it’s scary to rely on machines that have a lifespan of about 10 years and are making remarkable progress, and there are concerns about what happens in the unlikely event of a long-term power outage. Machine maintenance and filter replacement are inevitable and costly.
Isn’t it a natural premise to deal with the humidity of the building by how to build a house? A house that keeps the humidity balance and lives long and healthy is good.
This is the same for new construction and remodeling.
It is a matter of Japan’s climate and building. These big themes have a lot to learn from the wisdom and traditions of our ancestors.
The wisdom of the ancestors of Japanese buildings is to “touch the flowing air.”
Simply put, “ventilation”. Speaking of Tsurezuregusa, “How to build a house should be for summer”. It means that all the wood that makes up the house is exposed to the wind, and the wind passes through every corner of the room.
If you look at the old buildings with that kind of eyes, all the wood used is exposed to the flowing air, the wind blows through the house, and it is the best way to deal with humidity.
If the wood is constantly exposed to the flowing air, the wood moisture content will settle to 15% even outside.
This is called wood air-dry moisture content, and it will eventually maintain balance even if there are seasonal or time fluctuations in humidity.
By the way, if the moisture content of wood is always 25% or more, wood-rotting fungi are likely to grow.
However, because it was so cold in winter, it was stuffed with heat insulating material and built with airtight foundations, sashes, building materials, etc., and it became warm in winter, but on the contrary, in summer it became high-temperature and high-humidity .
And as a countermeasure, the current mainstream of home-building is that the method of ventilation by machine is used all the time. This is an easy way.
Instead, why not borrow the wisdom of our ancestors and arrange “touch the flowing air” in a modern way?
Allow the wind to flow under the floor of the building, in all the walls, in the space on the first and second floors, in the hut space and in all the rooms.
Still, it is not so difficult to make an energy-saving house or a passive house with good heat insulation and airtightness, whether it is a new construction or a remodeling.
In fact, we have been making such proposals since 1977.