To avoid condensation, the appearance of humidity or mould, it is necessary to evacuate steam produced by activity within the buildings (showers, cooking, washing, drying, etc.)

 
Ventilation: indispensable to reduce condensation

On average, a 4-person family produces steam worth about 12l of water: under no circumstances should this steam be evacuated through the walls and roof! 
Only a ventilation system adapted to the home and its occupation can reduce this interior pollution, avoid water streaming down the walls, damaging coverings and, ultimately, the building. 
But a ventilation system should not dispense people from having to air their homes by opening windows when possible (if outside noise and smells, and possibility of intrusion make it possible) to completely renew the air, especially when doing housework or DIY. It is impossible to control the quantity of air by opening windows though and the renewal of air is punctual and incomplete and, in winter, calories are lost. Airing is therefore complementary to ventilation but cannot replace it.

NB: With or without a ventilation system, it is essential to open windows 8 minutes every day.
 

Which ventilation system?

With an extractor?

This type of ventilation is usually used for very humid rooms (e.g. bathrooms or kitchens) or even basements and cellars. The system is noisy, even though there are sound-proofed boxes that reduce noise. There is a major disadvantage: the air flow is not controlled. It only evacuates condensation or humidity and does not purify the air and does therefore not protect the building in the long term.

By natural extraction?

With a grid on the bottom and top of the wall, this system is a random ventilation that does not satisfy real needs. The air flow is not controlled, which can cause excess heating consumption in the winter and no ventilation in the summer. 
This system is mainly due to the presence of a gas cooker which, for safety reasons, requires sufficient air outlets.

By joins in the walls and so-called “breathing walls?

No ventilation due to defective air tightness of walls, windows, joinery, shutters, doors, etc. can be considered to be ventilation. It causes parasite air to infiltrate which does not allow good airing and could damage the durability of the building, the operation of smoke and ventilation ducts. Under no circumstances should so-called “breathing” walls be considered as airing solutions for houses.

By mechanical ventilation?

Good airing is only possible with controlled mechanical ventilation (CMV) to create permanent airing, modulated according to use and controlled in time.

NB: There are two types of CMV: single or double flow .

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