Central heating radiator position

[Steve4Physics]

TL;DR Summary

Best position for central heating radiator

Hi.

The general advice for positioning a central heating radiator seems to be to mount it under a window. The reason being that windows are cold spots and the falling cooler air from the window and the rising warmer air from the radiator help the formation of a convection current around the room; this assists heating-up the room quickly and uniformly.

But surely this increases heat-losses - because the hottest air is nearest to the coldest region (the window and the external wall on which the radiator is mounted).

My instinct would be, if practical, to put the radiator on an internal wall opposite a window. There should still be a convection current created but losses through the window/external wall would be reduced.

Any views/experience with this?

 

[Lnewqban]

My instinct would be, if practical, to put the radiator on an internal wall opposite a window. There should still be a convection current created but losses through the window/external wall would be reduced.

The problem I see with that is that cold air leaking through the windows will travel horizontally along the rooms toward the heater.
That creates discomfort due to a cold draft.

 

[jrmichler]

An old technology uninsulated house with single pane windows has wall R-value about 2 to 3 and window R-value about 1.0. Those old single pane windows were poorly air sealed, and leaked a lot of cold air. The outside walls are cold, and the windows even colder. Positioning heating units under the windows where they directly counteract cold drafts is best for comfort.

My own house is insulated better than code minimum with R30 walls, R3 windows, and air sealed to 0.85 ACH50. I had the heating registers installed toward the middle of the house in order to minimize duct runs. There are no cold spots or cold drafts. The entire house is at an even temperature, even at -30 deg F outside with the wind blowing.

 

[Steve4Physics]

The problem I see with that is that cold air leaking through the windows will travel horizontally along the rooms toward the heater.
That creates discomfort due to a cold draft.

The windows are double-glazed which don't leak but would still be a source of colder air. So I think you are right - there is the potential for a cold draft along the floor unless the radiator is under a window

 

[Steve4Physics]

An old technology uninsulated house with single pane windows has wall R-value about 2 to 3 and window R-value about 1.0. Those old single pane windows were poorly air sealed, and leaked a lot of cold air. The outside walls are cold, and the windows even colder. Positioning heating units under the windows where they directly counteract cold drafts is best for comfort.

My own house is insulated better than code minimum with R30 walls, R3 windows, and air sealed to 0.85 ACH50. I had the heating registers installed toward the middle of the house in order to minimize duct runs. There are no cold spots or cold drafts. The entire house is at an even temperature, even at -30 deg F outside with the wind blowing.

Thanks. I've modern double glazed windows but the walls aren't well insulated (1880s brick house) so you have a great advantage! On the other hand, the temperature here (Devon, England) doesn't drop to -30^oF (-34^oC)!