Radiators under windows.

Chris Pearson:

. . .


In practical terms, if you need to put furniture against the other walls, the space under the windows may be all that is available.


What you shouldn't do is cover the radiators with floor-length curtains. Unfortunately that is exactly what Mrs P likes and then she complains about the cold. ??

Consider a radiator installed away from the window. This sets up an air circulation pattern. Hot air rises from the radiator and travels just below the ceiling towards the window, from which cooled air sinks to near floor level and travels back to the radiator. People thus sit or stand in the path of the cooled air from the window, which can compromise comfort. To compensate for this, it is desirable to bring the mean room temperature higher than would be necessary if radiator were under the window, avoiding this circulation pattern. This offsets the gain achieved by having the radiator situated where its heat is less likely to leak outside.


So from an energy point of view, maybe fitting radiators under windows is not such a bad idea after all. Has any university or other organisation conducted any research to quantify these alternatives?


In my house, most of the radiators are under windows, thus no clash with furniture. There are a few exceptions, e.g. the bathroom, where the bath, handbasin and loo are all backed against the outside wall, so it is not practicable to put the radiator under the window. In the dining room the window is - well a french window, so the radiator clearly cannot go there.


Overall I think common sense has been applied in the positioning of the radiators (done by a previous owner).


As for curtains, I suggest these should be just long enough to reach the window sill, and sit on it without overlap.

Some interesting points of view, but if you have a super-insulated, hermetically-sealed, draught-free house, under the windows is just fine. That's if you need them at all.

It is interesting that it seems the common consensus is that under windows is the place to install radiators.


Apart from the possible waste of heat, placing electric heaters under windows has to be potentially dangerous as they may be covered with curtains if the users of the heaters don’t have the good sense not to cover them, as I have seen happen.


Andy Betteridge

BTW, a friends home built large but super insulated house has a modest heating demand, but would be uncomfortable with no heating. It is heated by a single loop of wide bore pipe through which water heated by a solid fuel stove circulates by gravity. No radiators are used, the pipe IS the radiating surface.

The heating pipe runs around the entire perimeter of the upper floor before descending to the stove.

This arrangement slightly restricts furniture layout, but has worked excellently.

With a good fire as would be used in winter, the heat output to the water is estimated at about 6Kw, with another 6Kw into the room containing the stove. About half that with a modest fire.

In moderately cool weather the fire is lit each evening and allowed to go out during the night. In colder weather the fire is lit 24/7.

I know someone who thinks drying clothes on a (wet system) radiator is a fire risk. I suppose overcaution is better than gliby drying clothes on electric storage heaters though.

I have replaced thermal fuses in storage heaters, because people have tried to dry clothes, towels and sheets on them.

With postage you are looking at fifteen to twenty quid or more for the fuse  plus two visits to find out what the problem is and another to fit the new fuse, a wet towel can soon run up quite a bill.


Andy Betteridge