Good ventilation in our dwellings is important both to our health and to that of the house.
Good ventilation with heat recovery also saves energy, since the energy in the warm indoor air is recovered and transferred to the incoming outdoor air.
Before the 1970s
There are several different types of ventilation. Houses built before the 1970s are often not tight and natural draught ventilation is used, i.e. air flows out and in through gaps in the structure. The air circulation is poor, particularly in the summer, since there are no temperature differences between outdoors and indoors to drive the air circulation, and the energy loss is high.
In the 1970s
Houses built in the 1970s were tighter in order to save energy. But in many cases, nothing was done to the ventilation, and there are therefore many houses today that have a poor indoor climate, and moisture and mildew problems.
From the 1980s onwards
Houses that were built from the early 1980s onwards often have mechanical exhaust air systems or supply and exhaust air systems.