eli5: Why are radiators in houses often situated under a window- surely this is the worst place and the easiest way to lose all the heat?

Question

eli5: Why are radiators in houses often situated under a window- surely this is the worst place and the easiest way to lose all the heat?

In: 2851

Answer 1

It’s because the cold windows are the greatest heat loss from the room and the radiator under the window causes a rising current of warmed air in front of the window. It counteracts the cold down draught generated by the cold window.

If you were to put the radiator on the opposite internal wall (as seems logical) then you’d get the warm air rising to the ceiling, flowing across the ceiling and a descending draught of cold air flowing down past the window and across the floor. The warm up-draught from the radiator and the cold down-draught from the glazing would reinforce each other, The strong cold draught flows across the floor. People are most sensitive to cold draughts around their ankles.

It was more important in the days of single glazing and steel window frames.

TLDR: Radiators are placed under windows so that the rising warm air will counteract the cold down draught generated by the glazing. If the radiator were on the opposite internal wall, the cold down-draught and the warm up-draught would reinforce each other, which may prove uncomfortable.