Keep the coolness of the night until the daytime

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A house where you can enjoy the heat of nature. That is the first step towards building a healthy home.

However, it is not uncommon these days for the temperature to exceed 35 ° C. No matter how much you want to enjoy the natural heat, it may be a little too hot.

A house where you can sweat comfortably in the heat of nature. It requires some ingenuity.

It’s a passive house. Passive Solar house . It is a system that can use natural energy in an architectural way.

Many people think that the old house was airy and cool due to the layout of the Japanese Kanji 田 .

I would like to say that is true, but the answer is only half correct.

The outside air is 35 ℃, and even if the wind blows through the room, the temperature of the passing wind is 35 ℃.
It’s never a cool temperature. If the outside air rises by about 2 ° C, it will be higher than the body temperature.


If this happens, the wind that hits the skin itself becomes unpleasant.

It is cool only when the cold wind blows to some extent.


In summer, temperatures often exceed 30 ° C early in the morning.
In such a case, just opening the window and letting the air through does not always make you feel cool.

It is often called “coolness in the shade” to express the coolness of nature, but it is not so easy in modern houses. The coolness of the shade is the comfort you get when the ground under the tree is cold without direct sunlight and when you are exposed to the wind below your body temperature.

In indoors, to get the coolness of the shade of tree , the temperature of the walls, floors and ceilings must be much lower than the body temperature, just as the ground under the trees is cold. If a cool breeze blows there, it’s just the coolness of the shade.

Modern houses can’t let the heat escape . As a result, it is common for walls, floors, and ceilings to get hotter than the outside air, and in addition, the heat insulation has improved, so the heat does not escape even at night. This made the air conditioner a necessity.

In modern houses, at least two factors are required to get the coolness of the shade of trees.

First, it has the function of dissipating the heat that has entered the room to the outside.

Second, it has the ability to lower walls, floors, and ceilings below the outside air.

The presence of these two functions at the same time keeps the walls, floor, and ceiling below the outside air, making it possible to achieve the coolness of the shade of trees.

I would like to see what kind of architectural method will be used to achieve this.

First, let’s look at the architectural method of dissipating the heat that has entered the building. This depends on two methods. First, prevent the heat from entering the building as much as possible. The second is to quickly eliminate the heat that has entered.

The places where heat enters the building are the roof, walls, foundations and openings and all the exterior surfaces of the building. First of all, it is necessary to insulate all these surfaces well.

The roof surface, wall surface, and foundation surface are constructed without gaps by the method of external insulation. Similarly, guard the opening with a pair of glass with high heat insulation performance.

It is a method to completely insulate the entire house, but with that alone, the heat will still be trapped.

Insulating heat so that it does not enter means that, on the contrary, the heat generated inside the building and the heat that has entered from the outside cannot escape to the outside. This is the insulation dilemma.

Two ventilations are needed to solve this dilemma.

PAC住宅夏の空気の流れ

The ventilation that flows through the room and the ventilation that flows through the invisible skeleton space such as the attic, the inside of the wall, and the underfloor space.

The heat that is trapped directly in the room is removed by the ventilation of the room, and the heat that is trapped in the space around the room is removed by the ventilation of the space inside the structure of the house.

This is not possible with the LDK floor plan that is divided in the central corridor, and the method of filling the walls, ceiling, and floor with heat insulating material. In this regard, most modern houses are disqualified.

A further point is to take advantage of the coolness of the night to keep floors, walls and ceilings during the day even slightly lower than the outside air.

This also requires two elements. One is the function to bring the coolness of the night into the building, and the second is the heat storage function to store the coolness until the daytime of the next day.

Old buildings had these two functions. All parts of the building were full of gaps, so the cool night breeze entered the room. And the clay wall played the role of a heat storage body. As a result, the interior was cool in the shade, as long as the walls kept the cold of the previous night, even in the hot breeze during the day.

The ventilation of the skeleton space brings coolness at night to the inside of the building. The solid foundation concrete in the underfloor space can be used as a heat storage body.

The coolness that was stored cold at night can be revived during the daytime by ventilating the space inside the body to bring the coolness to the floor, walls, and ceiling.

The modern version, the coolness of the shade of trees, is completed here as a passive house.

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