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?
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Many have pointed out that putting the under the window makes sense thermodynamically. Architecturally: radiators are often installed in niches. It doesn’t make sense to weaken the wall in more places than necessary. Since the window is a weak point of a wall anyway, you can get away with having thinner walls bellow it. Also, the windowsill will cover the radiator and you thus lose less wall space for shelfs and such.
Radiators don’t just work by heating the air immediately around them, they also start air currents driven by warmed air rising to the top of the room and cold air coming in from behind to replace it. The bigger the _temperature difference_ between cold and warm air, the faster those currents will move, and the less time it will take for all the cold air to pass over the radiator and get heated. So the most efficient place to put a radiator is the coldest spot in the room, which is traditionally under the window.
If you have a room with a window on one side where heat is escaping, and a radiator on the other, you’ll have a gradual drop in temperature across the entire room between the radiator and the window, and the side by the window will be quite cold
If the radiator is under a window, it will be warm there because it’s near the radiator, and the rest of the room will also be warm, because there is no where in the other part of the room for the heat to escape
If you have a room with a window on one side where heat is escaping, and a radiator on the other, you’ll have a gradual drop in temperature across the entire room between the radiator and the window, and the side by the window will be quite cold
If the radiator is under a window, it will be warm there because it’s near the radiator, and the rest of the room will also be warm, because there is no where in the other part of the room for the heat to escape
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There are lots of answers already, but I personally hate radiators and think it’s eapecially stupid to put them under a window (where I want to put a plant) and then put curtains around them so you are warming the one place on the wall with the worst insulation and putting a barrier around the whole situation.
Perfect old timey solution for when gas was almost free, the world wasn’t dying from global warming and money needed to go towards the fossil fuel industry.
These days: forget about radiators, get airco/heatpump and low temperature heating such as floor heating, and insulate (double glass at the very least)
There’s a great story behind it. The practice of putting steam radiators under windows dates back to the 1918 Spanish flu pandemic. It was believed that the flu was caused by bad air, so radiators were put under the windows to allow the occupants to leave the windows wide open to let in fresh air no matter how cold it was outside. The radiators would heat the incoming cold air.
Along with the heat distribution, especially old houses were built when energy was a lower concern than sickness. They were designed to be able to be aerated even in winter to better prevent air transmissable disease
I actually know the answer to this! It dates back to the 1918 influenza pandemic. Folks were told that they needed to keep their windows open to ventilate their houses. So they started putting radiators under the windows because back then you couldn’t really regulate the temperatures and that way it would still be warm but they could have the windows open as well in sick rooms. I went to an architectural Museum that explains this! So cool that I get to use this random crazy bit of knowledge.
Because that’s where the cold is. If you have your radiators in the middle of the room, you get hot spots in the middle of the house and cold spots near the exterior walls.
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