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?
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.
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.
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
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.
================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
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
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.
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.
=================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.
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
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.
================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
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
"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.
from clive email@example.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.
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.
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