Why ventilate?

Why ventilate?

The new role of ventilation

Strengthening of requirements on energy performance of buildings and the recent awareness of the air quality we breathe inside the premises now provide a new role to ventilation. The reinforcement of insulation and sealing of the housing no longer allows the natural air renewal by infiltration, and the search for savings on heating requires a better control of sources of heat losses, including those generated by the ventilation which represent an increasing part.

heat-losses-of-a-non-insulated-dwelling-2014Most of the components and equipments of constructions directly or indirectly involved in the energy consumption of housing such as windows, insulation, furnaces, etc. have benefited in recent decades for substantial progress to be optimized nowadays.Thus, today, the main source of energy savings is in ventilation. If this represents on average 20 to 25%  heating costs for uninsulated or poorly insulated housing, this level can reach 50% of heat losses on a very airtight insulated house. For this reason, it becomes essential to implement an effective ventilation system, advantageously combining energy performance and indoor air quality. Governments are increasingly aware of the role of ventilation, as most European regulations require and specify ventilation systems in housing and take account of their energy impacts through the existing thermal regulations.

Among the systems, one system advantageously combines the indoor air quality and energy savings: Demand Controlled Ventilation.

Ventilate: what for ?

The ventilation through windows: an obsolete and expensive habit

ventilate-what-for-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.


Indoor pollution sources

The first objective of a ventilation system is to ensure good indoor air quality, replacing stale air with fresh air from outdoors. While indoor pollution – a result of emissions from the human metabolism, indoor activities, and building materials and furniture – is a complex of many types of pollutants, humidity plays a remarkable and specific role in the residential context.