Consider a building in a cold climate with a temperature difference of 20 degrees C, i.e. external temp. is 0 degrees C and internal temp is 20 degrees C.
How does a building lose heat through a gap in the external wall?
Does the cold low pressure air draw the warm air out or does the warm moist air rising in the room leave a 'gap' below which draws in the cold air?
For the sake of argument, assume that the remainder of the building is hermetically sealed i.e. airtight, and the wall is a high performance wall e.g. U-value of 0.3W/m2K.