The ventilation through windows: an obsolete and expensive habit
Once, the energetic context, less tenses than currently, allowed us to consider the opening windows as an appropriate response to ensure a good level of hygiene in occupied spaces. Nowadays, the new energetic issue requires the implementation of an automatic ventilation system to ensure that function. Indeed, the quest for energetic performance is clearly no longer compatible with the old ventilation system. It’s now clear that the inhabitant can’t judge by himself neither the amount of air required to be renew, nor the air point of entry into the dwelling, let alone its duration. In a window ventilation situation, the amount of renewal air is either too low (too brief ventilation, or in a poor number of rooms), or too high (which causes severe heat losses, especially in winter). As an example, when the outside temperature is 5°c and the inside one is 21°c, the ventilation by the opening of a window during 10 minutes consumes about 1kW.h in heating, that’s mean 0.12 € with an electrical heating.
Opening a window during 10 mn in winter = 0.12 €*
Thus, a suitable and automatic ventilation system is the only way to guarantee an indoor air quality and energy saving optimum to the extent that it limits greatly the heat losses by removing the need of a ventilation through the windows, during the heating period in particular.
* Based on the average public electricity cost in France, estimate based on an internal temperature of 21°C and with normal conditions.