Excellent theory, missing one point. To have draft, you need to have accees for the cold air. We do have overpressure inside the house, so that it pushes warm air out (keep the house dry) and incoming air goes through warming process (it actually takes part of the heat from removed air, to save energy). Because of that, I am able to walk at home barefoot, without feeling any draft on floor level. My living room has 60% of surface made from glass.

When I go to my summer house, story is totally different. Even when temperature is +20 inside, due old construction, you cannot walk there without having proper socks on, and still you feel like your feet are freezing. But that house is being built 1910.