Air current direction at doors/doorways without air currents
Different thermic relations between the outside and inside conditions of buildings lead to air masses of varying pressures. The laws of physics tend to equalise these pressure differences.
This effect creates air currents that are particularly apparent around doorways. Hot air leaves the interior through the top part of the doorway, while exterior air penetrates the interior through the bottom part of the doorway.
The result is draughts and uncomfortable sensations of coldness that reach well into the building interior. Wind pressure also contributes to this exchange of air, especially where there are exits inside the buildings, such as other doorways, windows, unsealed roofs or other leakages.
An optimally located air curtain installation can provide effective screening against doorway thermic effects and to a lesser degree against air intrusions (wind pressure). This can be done by an air curtain that generates an air current of adequate temperature at floor level to provide additional heating in the interior or at least ensure a constant inside temperature.