Radiators under window--WHY?

johneym

replumbing old house an would be much handier to put radiators on inside wall and not under window. However all the plumbers say it should be under the window because thats the way it always was/is ?
Why?
Does it not make more sense to have the heat flow across the room before it exits the window etc.
I know in my home house the heat from the radiator just goes behing the curtains and out the window.

jpfahy

When I was replumbing mine I moved the downstairs radiators away from the windows without any problems. In bedrooms the only free space is usually under the window. It is said that you can get staining on the wall above the radiator due to the convection but I haven't seen it.

cdb

I asked an environmental engineer this very question maybe 10 years ago and if I recall correctly was told that the window is the coldest part of a room, placing a radiator underneath it counteracts the cold air rolling down off the window. There is also a turbulence effect which helps to disperse the heat. Not sure if this still applies with modern radiators and improved insulation but it may be the reason.

drBill

I presume it's not governed by regulations as in most newish houses I've seen recently, all radiators were away from windows.
Personally I think under the window is a bad location because, as you say, closing the curtains has the effect of partially shutting the rad out or the room.
I've also heard the argument about this helping to counteract convection at the window but never really understood why convection was supposedly such a bad thing compared to blowing heat at the window.

wonderfulname

Because the cold air off the window sinks, balancing the rising warm air from the radiator, this keeps the heat closer to the ground where it is of most benefit. The absolute worst is to have the radiator on the opposite wall to the window, as that can create quite a strong circulation - pushing cold air across the floor and warm air along the ceiling, much like this JC Science expt. demonstrates. (link) drBill, this is why convection is such a bad thing, hot air rises so you have all the benefits of a heated ceiling and a frozen floor! The downside of placing a radiator under a window is that your losing heat through the external wall, putting the radiator on an internal wall would mean this heat would be absorbed and given off by the wall.

However this isn't as big an issue with double glazing, as you might imagine..

yoshytoshy

I automatically put radiators under windows in bedrooms but, in other rooms usually leave that up to the homeowner.

Very seldom you'll see any furniture under a bedroom window, thats why I put the radiators there.

Micky Dolenz

2 reasons.

Available wall space and convection. Warm air raises from radiator and meets cold front of window, this causes the warm air to tumble and circulate around space.

Very important that long curtains are not fitted where there are rads.

Joey the lips

I live in a timber frame house and asked the builder why the rads were not under the windows in the bedroom and he told he that in a timber fram house it is not necessary as the room vents bring in air.

Now i dont know if this was a load of bull and tbh i could not find anything on it in building regs...Granted i did not look too hard.

My wife loved where the rads were as they were on walls behind doors so no furnature there either..

tbh i think under the window is the best place as its the best use of a dead space..