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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Same reason that supermarkets have air conditioners above the doors blowing cold air during the summer. It’s to block the undesirable temperature from getting in.
Nobody’s talking about the uniformity of the room temp. If you put a radiator at the opposite side of the room you will have a hot spot and a cold spot in the room neither of which is confortable.
Hot air from a radiator doesn’t actually mix that well with the rest of the cooler air in a room.
When I give my kids a bath, I fill the tub with very hot water first (cast iron tub soaks up a lot of the heat, so we have to warm up the tub itself as well as the water). After some point we add cold water.
But adding cold water doesn’t actually make the bath water an even, cooler temp. So I have to stir the water continuously so there are no pockets of hot water.
Same for air. If there is no air movement in a room, the hot side will stay hot and the cold side will stay cold. But cold air forms a draft of cool air current because cold air wants to drop to the floor. (Cold air is denser than warm air). The movement of cold air falling to the ground creates an air current that can stir the room air.
So air moving over the radiator helps to move all of the air around the room, instead of having hot spots and cold spots.
I’ve tested this myself with electric oil radiators that we used to put on the far wall away from the window; and later learned to move it under a window or in front of a cracked interior door.
I guess the best way to explain it like you’re 5 is this: the reason you think it’s the worst spot is actually the exact reason why it’s the best spot.
Think about what insulating is doing, keeping the warm air from going outside because that’s how you lose heat, it goes outside. It can only possibly go outside by going through an exterior wall. Therefore, heat is only required on exterior walls where the heat is escaping, only to replace the heat lost. Placing it by the worst spots, windows, gets you the most even heat distribution, the heat is only counteracting the loss, and the rest of the building stays a constant temperature because the interior isn’t losing heat to the cold exterior.
Also, this is NOT true for AC, AC counteracts the hot air outside, the hot air from all the electronics, lights, stoves, etc, and it counteracts body heat. Therefore AC needs to be distributed throughout the building, and really big buildings need so much AC that many don’t need heat even when it’s very very cold outside because their internal heat from running stuff is more than they lose through exterior walls.
This is wonderful new information I did not have. I also wondered why and this makes perfect sense!
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.
I read that radiators were originally designed to be used with an open window during the 1918 influenza pandemic
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.
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
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