What is the "chimney effect" or "stack effect"?

In simple words - it means that the correct chimney works like a vacuum cleaner and draws air from the room to the outside.

This is due to the temperature difference between the room and the outside.

When the chimney is too short, the chimney effect may sometimes not work or it will be difficult to initiate it

A chimney of the appropriate height will work well even if there are any gaps in the joints