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First of all, it must be airtight. C value is an indicator of airtightness performance. We set the target value of C value as 0.1 (cm2/m2). The required value is set at 0.3 (cm2/m2). We believe that any construction company can achieve this goal if they do what they need to do carefully.

To ensure airtightness, we recommend using two layers: a moisture control layer on the indoor side and a panel layer on the outside wall. With this method, you should be able to achieve 0.3 (cm2/m2) with just a little attention to detail.

​ Sd value is an index of humidity control performance. If the air layer is equivalent to 2 m based on the air layer of 1 m, it is expressed as Sd value = 2. In Japan, we have always used only sheets with an abnormally high Sd value called airtight sheets. Recently, moisture management has finally started to be considered. We recommend a variable type moisture-adjustable sheet whose Sd value changes depending on the humidity.


Insulation prevents heat from escaping from indoors to outdoors (the opposite is true in summer).

The U value (heat transmission coefficient) is a value that indicates insulation performance. The smaller the U value, the higher the performance. The U value is calculated for each part of the roof, walls, windows, etc. The Ua value is the average value of each U value according to the area ratio.

Generally, this Ua value is used to evaluate the insulation performance of the entire building. The 2020 standards set the Ua value at 0.87 (6 regions), which is the minimum standard. If you're going to build a new house, you'll want to keep it below half that, 0.43. If you want to reach the PassiveHouse level, you should aim for 0.15.

It is up to each designer to decide how to meet the standard, but if it is around 0.43, it is quite possible to meet the standard by extending the conventional filling insulation.

​Solar radiation acquisition and solar radiation shielding

In order to take in solar heat, we want to take in sunlight as much as possible, which is called solar radiation capture.In the summer, we want to avoid sunlight as much as possible, and in winter, we want to take in solar radiation, so we want to prevent sunlight only in the summer, which is called solar shading.

 Using the power of nature to provide heating and cooling is called a passive method.

It is desirable for any type of building to be adjusted so that it receives less sunlight in the summer and more sunlight in the winter. To make these things possible, you can block sunlight by using eaves, eaves, deciduous trees, blinds, and blinds.

For openings such as windows on the south side, eaves and eaves are mainly used. On the south side, the difference in solar radiation acquisition and the difference in solar radiation angle between summer and winter have a large effect, so it is possible to prevent solar radiation gain by using the solar radiation angle with eaves and eaves. In addition, by using deciduous trees, the leaves block direct sunlight in the summer, and in the winter, the leaves fall and allow direct sunlight to enter.

Blinds and blinds are mainly used for openings on the east and west sides. Since there is little change in solar radiation gain from east to west throughout the year, it is possible to prevent solar radiation gain with blinds and blinds.


​Heat storage

The purpose of heat storage is to shift the peak times of indoor and outdoor temperatures. It also slows down changes in indoor temperature.


By effectively utilizing heat storage, it is possible to reduce indoor temperature changes to 1/5 and shift the time of peak temperature by 12 hours.


When considering heat storage, we recommend using wood insulation material. Wood insulation materials do not have particularly good insulation performance, but their heat storage performance is outstanding.


 換気については、 長く明確なことが言えない時期が続きましたが、そろそろ、明言しても良いように思います。





​Air conditioning & humidity control equipment

This refers to air conditioners and dehumidifiers. These are evaluated using indicators such as heating capacity and cooling capacity. If you want to give a specific number, a hair dryer has a heating capacity of about 1000W. On the other hand, a household air conditioner called a 6-tatami type has a heating capacity of 2200W.


​ Nowadays, it is possible to design a house that can heat the entire house with just one hair dryer. On the other hand, in summer in Japan, dehumidification is a must, so we have no choice but to rely on air conditioners.

Energy creation/storage

Examples include solar power generation, solar water heaters, and storage batteries. Since there is a lot of expensive equipment, we try to create a design that does not rely on these as much as possible.

Let it happen...

○Airtight performance 18.4.10

 This is all about PassiveHouse, but PassiveHouse requires an airtight performance of 0.3 or less in terms of C value. This is a performance that would be impossible for a construction company with low awareness, even if they were to do a handstand. However, the first important point of a highly airtight and highly insulated house is airtightness. First of all, there is airtightness, and then there is insulation. It's the same logic that no matter how warm a jacket you're wearing, if your stomach is exposed, you're cold. Be sure to have the construction company measure the airtightness. You can test it for about 50,000 yen at most.

○ Will heating equipment become unnecessary? 18.4.10

Is an underfloor air conditioner or fireplace necessary? As you improve the insulation performance, there comes a point where the indoor heat generation exceeds the heat loss. PassiveHouse aims to achieve this point. In PassiveHouse level homes, underfloor air conditioners can cause overheating and overdrying even in winter. If you put a fireplace in PassiveHouse, it will become just an interior decoration. In fact, it may be a negative factor because the chimney hole reduces airtightness. By the way, indoor heat refers to heat generated by the human body and heat generated by household appliances.

○Winter futon will no longer be needed 18.4.9

If you increase the insulation performance to the PassiveHouse level, you will be able to sleep with just a summer futon or blanket even in the middle of winter. Improving insulation performance can lead to reduced storage space.

○The concept of ATMM 18.4.9

ATMM stands for Air Tightness & Moisture Management. Up until now, PE sheets had been placed on the inside of the room to prevent moisture from entering the walls, but this did not prevent condensation from forming inside the walls in the summer (condensation inside the walls was allowed). In Europe, there are moisture-control sheets with graded moisture permeability resistance values, which are used differently based on the ATMM concept.

Even in Japan, variable humidity control sheets called Intello and Zabarn have been used in a small number of homes. Several new products have been announced here.

There is also software (WUFI) that simulates the effects of humidity over a three-year period using AMeDAS data. It cannot be said that these simulation methods have yet been fully evaluated in Japan. For some insulation enthusiasts.

It seems like it will still take some time for this concept to become widespread.

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