Ventilate: what for?
Ventilation through windows: an obsolete and expensive habit
In the past opening windows was an appropriate means of ensuring good indoor air quality in occupied spaces. However now that energy efficiency has taken a much greater level of importance, this function is best served through the installation of an automatic ventilation system. Indeed, the quest for energy performance is clearly no longer compatible with simply opening and closing windows. It is almost impossible for the inhabitant to judge the correct level of ventilation required, the optimum point of entry of air into the dwelling, or its duration. With ventilation provided by open windows, the amount of air renewal is either too low (with windows open for too brief a period of time, or in a limited number of rooms), or too high (which causes severe heat loss, especially in winter). For example, when the outside temperature is 5°c and the inside temperature is 21°c, the opening of a window for 10 minutes can account for a heat loss equivalent to 10KW/h of electricity. An average loss of £1.25!
Opening a window for 10 minutes in winter = £1.25*
Therefore, a suitable and automatic ventilation system is the only way to guarantee indoor air quality and energy efficiency, by greatly limiting heat loss and removing the need to ventilate through the windows, particularly during the heating season.
* Based on the average domestic electricity price of 12.5p per KW/h, with an internal temperature of 21°C and with ‘normal’ weather conditions.