What is that much talked-of Passive House?
If we wish to define Passive House strictly, we could say that it is a building whose energy consumption does not exceed 15KWh/m2 per year. Demonstrating it in a different way from figures, we can say that a Passive House is a building that does not need a conventional heating system due to its low heating requirement. In order to make it practicable it is recommended to take certain issues into consideration as early as designing. It is important that the building is as compact as possible, just as much as its orientation.
Of course passive house there are – quite a few – requirements concerning the building materials. Walling, doors and windows, roofing, etc. of adequate quality are essential, since we aim to construct buildings with heat leakage reduced to the minimum. A completed Passive House may gain energy in various ways such as the body heat of the people and animals inside the building, heat getting through the walls and windows oriented in the required directions, or the Earth’s own energy. Beside these, a ventilation system is needed, which provides fresh air supply.
In order to obtain the Earth’s energy a so-called earth-collector is needed. The ventilation system draws in fresh air through this earth-collector. To understand how it works we need to know that 1-1.5 metres deep down in the soil there is a constant temperature of 6-9 degrees Celsius, independently of season or part of the day. In order to be able to utilize this condition, we need to lay down a tube that is 35 m long 200 mm in diameter, into the soil. Through this tube, fresh air drawn in is pre-warmed (or pre-cooled when needed). The ventilation system has to have a recuperator (fresh air has to pass through a heat exchanger, which transfers the warmth of deflated air to fresh air let in). The recuperator’s degree of efficiency has to be at least 80% in order to achieve the desired effect. The method of leading airtubes under the ground has another advantage, that is that the ventilation system cannot ice up, so no extra energy needs to be expended on preventing glaciation.
The question arises whether the profit gained by saving heating energy is lost with operating the ventilation device. The consumption of recent modern devices is about 1/10 of the saving, so the profit does not get lost.
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