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Losses due to ventilation in a highly insulated house can account for 50% of total heat loss. In short, the better insulated a home, the more airtight it needs to be; a comparison is often drawn with the thermos flask. However, the house must continue to breathe, ensuring the replenishment of fresh air. The Walloon Region requires precise calculation of this replenishment rate.

  • Natural ventilation
  • Natural ventilation is based on the principal of the slight depression existing between the two opposite sides of a building. Air enters one side through gaps and open windows and leaves on the opposite side. It is simple, effective, easy and cheap, but there is no control over the air renewal rate. The system depends solely on changing atmospheric conditions and the habits of the building's occupants.

  • Simple mechanical ventilation
  • Air intake or extraction fans are designed to ensure a mechanical draft, whatever the atmospheric conditions. Air inlets guarantee the necessary supply of air. This inexpensive system is effective and ensures the desired replenishment rate, but has the drawback of permanently bringing cold air into the dwelling and expelling warm air (and therefore calories).

  • Cross-flow ventilation
  • In this case, ventilation is fully controlled: fresh air is warmed up in a cross-flow heat exchanger, making use of the calories still present in the air being expelled. The system is power operated and adjusts airflow in line with fluctuations in the indoor and outdoor atmospheres. A number of sensors can be connected to the system: temperature, atmospheric humidity, and so on.

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