Why is modern underfloor heating more efficient than radiators?
• Radiators are invariably placed beneath a window because of the way convection works. If they were sited on the wall opposite a window, the cooling air dropping from the ceiling would be cooled more quickly as it met the cold window glass. This would create an uncomfortable downdraught from the window and pull cold air onto the floor. Sitting them beneath the window minimises any downdraught. The consequence is that the hottest air in the room – just above the radiator – is right by the weakest thermal link in the whole room and a lot of energy is lost immediately, through the glass. This is the primary reason why we have all been persuaded to invest in double- glazing over the years, to cut down these losses. After dark, we make matters worse by closing full length curtains across the windows and the radiator. With underfloor heating, radiant energy from the floor which strikes the window glass is almost entirely reflected back into the room, and the only losses through the window a
