Natural ventilation: what is it?

Unlike mechanical ventilation, natural ventilation consists of bringing in airair fresh air from the outside and to reject the stale air only by effect of convection to renew the volume of air from a room.

Appeared in the 1930s, this principle of ventilation still equips many old houses today. Previously, the ventilation of a house was simply ensured by the bad air tightness door and window seals… An ineffective process (and somewhat dangerous to health), replaced in order to facilitate the passage and renewal of indoor air.

An economical ventilation system

The principle of natural ventilation is quite simple. The walls of rooms (kitchen, bathroom, toilets, etc.) are equipped with two grids ventilation. The first in the lower part corresponding to the arrival of fresh air, the second in the upper part to reject stale air outside. A simple principle based on the convection effect produced between the difference in density of cool air and hot air (the latter being lighter). Air circulation is also facilitated by the presence of a chimney flue or hood. Economic ventilation system, it does not require major work to install ducts and box.

Natural but insufficient ventilation

However, to correctly renew the volume of air, this ventilation principle is not the most efficient and quickly reaches its limits. In the chapter of the disadvantages, let us quote the difference in temperature between the interior and the exterior which varies from one season to the other favoring more or less the principle of convection, a debit of air coming from the outside naturally not constant… points which led to the abandonment of this mode of ventilation in favor of the current mechanical ventilation devices.

Improve ventilation in the old

To enjoy better indoor air quality in an old house, it is possible to eliminate natural ventilation. Depending on the configuration of the premises, two solutions are available to you. If the configuration of the premises allows the passage of a duct, the installation of a CMV (controlled mechanical ventilation) is recommended because of its very good efficiency. If installing a CMV is not possible, the solution requires the installation in damp rooms of a extractor of air instead of the upper ventilation grille. From natural, ventilation becomes distributed (VMR). Depending on the needs, the air extractor can be intermittent or permanent.