Question:What causes draughts?
Some students are convinced that draughts are caused by it being windy outside the house. But actually you would feel a draught even if there is absolutely no wind outside the house.
Draughts are caused by convection currents inside your home.
Convection currents are moving air caused by heating due to the heat sources in your rooms.
The reason we feel a cold draught is because the air in a room is usually moving due to convection currents.
When the moving air finds a gap under a door or through a vent, it will move that way too.
Since warm air is moving outwards, there must be something moving back in, and this will be air from outside which will be colder.