Radiators below windows

Hi,
Is there a standard or good practise rule for siting rads under windows? I mean is there a minimum separation between the top of the rad and the sill?
TIA, W
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W wrote:

I suspect not - unless things have changed in recent years it still appears to be the best place to site radiators as a) their is usually space below the sill and b) it reduces heat differences across the room (windows are a source of heat loss), if you re planning curtains then its better to have a gap between the sill and radiator such that the curtains can sit above the radiator, but not block the radiator when its on (i.e. avoid full length curtains) - all common sense I suppose?
Jon
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Most Central Heating advisers state that radiators should never be put under windows but on inside walls. My new house has most of the radiators on inside walls with only one under a window which could not be avoided. Blair
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No, to both questions. But, it is good practice to fit shelves above radiators sited under windows. The shelf helps to throw heat back out into the room instead of letting it disappear directly upward and get lost by the cold air falling off the inside of the glass.
It's also best if radiators are being fitted under windows, that curtains do not cover them and isolated them from the rest of the room. Curtains over the rads' will trap hot air between the glass and the material, which is not a good idea if it's the room you want to heat.
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Then they are most definatley wrong ,they should be positioned under a window to warm up down draughts from the window and most manufactuers quote a height from ground to the bottom of rad of 200 mm. If positioned on a inside wall then they have been fitted for the convience of the installer and not the end user
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quote
subject.
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Alex wrote:

    Disagree. Radiators under windows is an old idea from the days of poorly insulated houses. The female modern user wants to hang full length curtains over windows, therefore the radiators need to be placed elsewhere. From an energy conservation viewpoint, full length heavy curtaining over widows is much more efficient than short curtains. Placing radiators under windows simply throws money away through the glass.
    Regards     Capitol
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================It used to be said that the best place for radiators is under the window because that's the place for greatest heat loss. This was based on the need to heat the coldest part of the room to provide the most comfortable arrangment. Since double glazing became more common it's easier to be more flexible about siting radiators because of the lower heat loss through DG windows.
It's also possible to choose radiators of different heights to avoid problems under window cills. For example, 15" or 18" radiators will fit under most windows although they will obviously need to be longer to achieve the same heat output as a 24" rad which appears to be the most popular choice.
Cic.
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need
When I worked for Potterton many many moons ago I was told that the under window situation was to counteract the draft (draught?) created by cold air falling down the windows. Obviously over the intervening years advice has changed as you say.
-- Malc
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I know this siting of rads under a window is "standard practice" and all the books reproduce the same diagram of hot air rising to balance cold air off the windows - and that's how I had my rads installed.
Sorry, I think, and it is just an opinion, that is all bogus.
With good double glazing and "thermal barrier" window frames I would now buy quality lined curtains that went to the floor of every lounge and bedroom window. Then install "skirting rads" all the way round the room. The lined curtains could sit "on top" of these skirting rads. Then the warm air would be in front of the curtain and heat the room.
Also such rads would be visually less intrusive than big panels and make the siting of furniture much more flexible.
With high levels of insulation, good heat recovery ventilation to remove the dreaded condensation and draft exclusion - although I have made no calculations - the heat output from rads to the living space versus heat loss (which must be the important factor) should be sufficient for a comfortable environment.
Thoughts?
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=================The only skirting radiators I've seen (Finrad) were not sufficient to heat a room adequately. I believe they're really only suitable for background heat. They have virtually no residual heat because they consist of only a single 22mm pipe covered with aluminium foil fins and this means that the boiler would be constantly switching on / off.
Heavy curtains are pretty good at keeping heat in but of course they're not so useful during the day.
Cic.
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That's what I've got ...

Total b****cks!

One wonder what else the writer believes ...?

What is residual heat ... let alone virtual heat ...

The reader is left to ponder the total surface area - that's the bit were heat, from the water, is transferred to air, from all these aluminium fins conpared to that of a radiator. BTW, 'radiators' don't work on radiation but on convection.

No, the boiler on/off cycle is a function of the heat transferred (or lost if you prefer) from the heated water loop to the air.
Having selected a 'skirting-board radiator installation for my bay-windowed lounge more that twenty-fives ago I flatly contradict the 'beliefs' of 'Cicero'. S/he must be either stuck on hypocausts or have no practical experience of Finrad installation in the home. Because the installation is unobtrusive and doesn't dictate the positioning of furniture many visitors have 'observed'; 'you haven't got central-heating -how do you keep the rooms so warm?"
There are places where the installation is inappropriate - bathroom and hall in my place. but from an inital installation in one room ( because of the bay-window) I re-fitted 'conventional' radiators with Myson finrads on subsequent redecorating of other rooms.
--

Brian



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<snipped

================I installed Finrad skirting heaters in my new house in 1976 on the recommendation of a heating engineer employed by the place I bought all my components. I found them totally inadequate for most of the time and I replaced them completely with conventional radiators inside 6 months. The improvement was immediately large and noticeable. As far as being unobtrusive is concerned that is a matter of personal opinion but I found them to be more invasive than conventional radiators. Fitting what amounts to an extra skirting board 8" high x 3" deep around most of the perimeter of a room is not really unobtrusive for most people. Many downstairs rooms have 2 or even 3 doors and getting pipework past these also adds to the problem of installation. The fitting itself is hardly convenient since each 'run' has to be fixed separately whereas a single radiator needs only 2 (possibly 3) brackets.
Positioning of furniture is hardly facilitated because every piece - bookcase, cabinet etc. - has to be positioned at least 4" from the wall rather than the more normal position close to the standard skirting board. It's a very unusual room which can't find space for a single radiator of an appropriate size for the room.
Skirting heating is technology that never really gained widespread acceptance because it doesn't compare favourably with more conventional radiators in most domestic situations. If it was as good as its supporters claim it would be much more widely used.
This quote from the 'Heating & Hotwater Information Council' puts the matter partly in perspective although it doesn't address the question of the inconvenient size of the units. Significantly, it points out the difficulty of finding sufficient wall space to provide adequate heating. It also suggests that combining skirting with conventional radiators is an option but that of course spoils the argument for greater flexibility in furniture positioning.
"Perimeter heating, commonly referred to as 'skirting heating' is an effective way of providing unobtrusive heat input into a room. The units, which are normally about 200mm high, run continuously at low level around the walls of the room at about 50mm from floor level. Although an attractive and effective method of heating, a difficulty sometimes experienced is to find sufficient wall space to accommodate enough skirting heating to satisfy the requirements of the room. It is quite feasible to combine a run of skirting with radiators if necessary. "
My opinion based on my experience is that a conventional radiator system is more suited to a domestic situation. If people want to experiment with skirting heating it's still available but it seems that most people are happy with the tried and tested system of conventional radiators.
Cic.
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Cicero wrote:

I agree. Its more obtrusive, than underfloor, and more expensive than conventional rads.
the worst of all possible worlds really

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Cicero wrote:

That depends ;-)
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from clive snipped-for-privacy@yahoo.com (Clive Long,UK) contains these words:

There is at least an element of truth in it but it is by no means the whole story which in any case depends on what you want from your heating. Those who hanker after the traditional effect (hot spot in front of the fire, cold corners) will no doubt take the professional advice and attach one radiator to the most convenient inside wall. Those who want a more even temperature across the room will have to take more rational measures, the easiest of which is to block the window cold spots by positioning a radiator under each window.
IIRC even the best insulated window loses more heat per unit area than the worst solid wall around so it makes sense to most people to avoid the cold spot cooling the adjacent area of the room by positioning the heat source between the cold spot and the room. In similar vein interior walls usually have little or no temperature differential between one side and the other so mounting a heat source on an interior wall promotes a temperature gradient across the room rather than reduces it.
The ideal solution (perhaps) is to install heating along each wall that mirrors the heat loss through that wall. Still tricky to compensate for the effect of outside doors though so don't have any in a living room.
--
Roger

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Clive Long,UK Wrote:

Yes I've heard this in architectural terms whilst many public building employ this system, yet I've never seen it in domestic use. Who sel such heating schemes
-- kafkaian
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wrote:

Hi,
Best to have a shelf over the rad as mentioned, but make the height and width of it so that when the curtains are closed they just rest on the shelf and don't go over the edge much. This will stop a down draught from the window getting into the room.
cheers, Pete.
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