Winter ventilation improves indoor air

During winter, people often keep windows closed to retain heat. However, during the night, the sleeper exhales water vapor that condenses on the windows and can contribute to mold growth. A quick action upon waking, called "aération éclair," is recommended to dry the room without cooling it down.

ADEME advises daily ventilation

The agency for ecological transition ADEME recommends opening windows wide for five to ten minutes per day, even in winter, to renew the air in a home without cooling it. This advice is particularly relevant for the bedroom, where a person exhales between half a liter and one liter of water vapor per night, enough to saturate the air in a closed room.

Humidity spreads during sleep

During sleep, the body breathes and sweats continuously, and this humidity spreads into a room that is often closed and poorly heated. The air then becomes charged with water vapor, more than any other room in the morning. Upon contact with the window, cooled by the outside, this vapor turns into fine droplets, a phenomenon of condensation, clearly visible as fog.

Ventilation removes humidity quickly

The correct reflex is a short but full opening. By opening the window wide and the bedroom door, you create an air current that renews the atmosphere in two to five minutes only, the time to evacuate the humid air before the walls cool down. Opening a single window also works, but the renewal is slower than with two opposite openings.

Long-term ventilation risks

Conversely, a window left slightly open for hours only exchanges a thin stream of air, cools the walls, and can even feed the mold around the frame. A brief opening, however, allows the walls and furniture to retain their heat, which warms the room again once the window is closed. Quick ventilation thus removes humidity much faster, while preserving the energy accumulated in the home.

Ventilation also reduces pollutants

Beyond the windows, this air renewal also evacuates the pollutants accumulated during the night, from exhaled carbon dioxide to compounds released by bedding and furniture. It is also better to avoid drying clothes or multiplying plants in the room, two additional sources of humidity. Less humid air also slows down mites, these tiny arachnids nesting in mattresses and first triggers of respiratory allergies.