Radiator Shelves

I've got the foil behind the radiators to help bounce heat out, will a radiator shelf also hep to reflect heat out into the room (rather than up the wall).

Also, I have one radiator that won't fit a radiator shelf (double radiator), would a floating shelf above it help?

Thanks

Michelle
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Comments

  • meames wrote: »
    I've got the foil behind the radiators to help bounce heat out, will a radiator shelf also hep to reflect heat out into the room (rather than up the wall).

    It will only reflect the heat to the edge of the shelf, then it will go straight up again.
    meames wrote: »
    Also, I have one radiator that won't fit a radiator shelf (double radiator), would a floating shelf above it help?

    Thanks

    Michelle

    No, radiator shelves are a waste of time, and if your radiators are below a window they will do more harm than good.
  • mech_2
    mech_2 Posts: 620 Forumite
    I don't see they can do any harm. If the curtains are hung above the radiator so that the hot air currently goes between them and the window then a shelf would seem to be a good idea.
  • mech wrote: »
    I don't see they can do any harm. If the curtains are hung above the radiator so that the hot air currently goes between them and the window then a shelf would seem to be a good idea.

    No, what happens is the warm air in the room gets cooled by the window. This cooler air falls to the floor and drags more warm air down to the window. This warm air then gets cooled and falls, dragging more warm air to the window to be cooled. It's a continuous cycle which gradually cools the room.

    If you have a radiator beneath the window, and it's on, it breaks this cycle and prevents the window cooling the air in the room.

    Putting a shelf above the radiator will stop the radiator sending heat up to the window and the cycle will start again.

    It's similar to having your fridge door open, the cold air falls out, dragging warm air from above into the fridge and making the fridge work harder to cold this air.
  • Interesting thread this is one I am working on at the moment so I had to do a search on it.

    The article below is from some green architects and might be of help.

    Search for this phrase: 'which would mean pelmets' in this link (read the whole paragraph the whole article is pretty informative though):

    http://www.eco-renovation.org/articles/view.php?viewid=266&W21ID=157

    According to the article, what you need is a closed pocket of stationary air space between the curtains and windows. Also if you have cavity wall insulation it seems that radiator reflectors may well be a waste of money. Shelves are also apparently not really effective (as mentioned above).

    A key question first of all might be whether the curtains are a good fit (eg does it feel colder between the curtains and window once the room has warmed up)

    Don't take my word on it though it seems to make sense to me but I am no expert.

    You might also get a better response on the DIY board.
  • grannybiker
    grannybiker Posts: 12,128
    Photogenic Name Dropper First Anniversary First Post
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    Most of my radiators are below windows, but I thought, (hopefully,) I'd overcome the problems as I always tuck the curtains between the radiator and the wall, or, if they're too short, tuck them up onto the window sills.
    Have I been wasting my efforts doing the above?
    The space between window & curtain is always much colder once the room warms up.
    (Old cottage, thick stone walls/ windowsills.)
    Worse things will have happened in the world today...
    "The only thing that really matters, it to love and to be loved."
  • Hi grannybiker,

    I have a radiator underneath my window in the living room and bedroom. In the living room I have a 2" overhang on the window sill so I have put two overlapping lengths of net curtain wire underneath the sill. When I close the curtains I pull them in front of the wire and tuck them underneath and up behind the wire. This seems to heat the room a bit quicker.

    In the bedroom I have a foot recess in the window so will fit either removable shutters (not sure about material and aesthetics though) or thicker curtains. Getting a good seal seems to be the way to go so I am going to try that and keep an eye on humidity.
  • Thanks for replies

    My radiators aren't under windows, some are on other walls, others are situated next to the window (but not below).

    Thanks

    Michelle
  • mech_2
    mech_2 Posts: 620 Forumite
    No, what happens is the warm air in the room gets cooled by the window. This cooler air falls to the floor and drags more warm air down to the window. This warm air then gets cooled and falls, dragging more warm air to the window to be cooled. It's a continuous cycle which gradually cools the room.

    If you have a radiator beneath the window, and it's on, it breaks this cycle and prevents the window cooling the air in the room.

    Putting a shelf above the radiator will stop the radiator sending heat up to the window and the cycle will start again.

    It's similar to having your fridge door open, the cold air falls out, dragging warm air from above into the fridge and making the fridge work harder to cold this air.

    That doesn't make any sense. You can't reduce heat loss through a window by making the air in front of it warmer. Quite the reverse.

    You want to seal the window off from the warm air in the room as much as possible using the curtains. The best way would be to rest the bottom of slightly long curtains on the window sill. If there's no window sill, a radiator shelf would seem a good idea (or tucking the curtains behind the radiator, but I don't like doing that as it will reduce the performance of the radiator by interfering with convection up the back of the radiator).

    However, for radiators positioned away from windows I can't see shelves being any advantage besides being useful to put things on.
  • Ken68
    Ken68 Posts: 6,825
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    Hi Meames, a good thread
    Hi grannybiker,

    I have a radiator underneath my window in the living room and bedroom. In the living room I have a 2" overhang on the window sill so I have put two overlapping lengths of net curtain wire underneath the sill. When I close the curtains I pull them in front of the wire and tuck them underneath and up behind the wire. This seems to heat the room a bit quicker.

    In the bedroom I have a foot recess in the window so will fit either removable shutters (not sure about material and aesthetics though) or thicker curtains. Getting a good seal seems to be the way to go so I am going to try that and keep an eye on humidity.

    Last year I made up some removeable exterior polystyrene shutters, to those d.g. windows at the back of my house, north facing.
    Immediate savings of £20 for half a winter, and they cost £20 to make. Not heavy, take them down about 9am and put them back at dusk.
    Another upside was NO CONDENSATION on the inside of the window.
  • mech wrote: »
    That doesn't make any sense. You can't reduce heat loss through a window by making the air in front of it warmer. Quite the reverse..

    Sorry, I didn't expand my sentence enough.
    If you have a radiator beneath the window, and it's on, it breaks this cycle and prevents the window cooling the air in the room.
    By this I meant that you prevent the window cooling the air that is in the room. Instead the air rising from the radiator gets cooled. But as this air is hotter than the surrounding air, and it is rising past the window, it gets cooled less.

    Imagine you have a room where all the air is at 25 degrees, and you don't have a heat source in the room. Also imagine that the room is well insulated and is not losing heat any other way but via the window.

    The air near the window gets cooled to 21 degrees. It then falls to the floor and drags air from above it down to the window. The air is at 25 degrees, but cools to 21 degrees and falls to the floor, dragging more warm air down from the ceiling to the window.

    In time all the air that is at 25 degrees will be dragged to the window and cooled to 21 degrees. Then your room temperature would be 21 degrees.

    If you had a radiator on what would happen is this. Hot air from the radiator would rise up past the window. But as it is hotter than the air in the room, lets say 28 degrees, it rises fast and doesn't stay near the window long. Because of this it only cools to 26 degrees. This means it is still hotter than the air in the rest of the room.

    It also prevents the air that is in the rest of the room, at 25 degrees, from getting near the window and being cooled to 21 degrees. You are still losing heat through the window, but that heat is being lost from air that is hotter than the room temperature anyway. So the overall temperature of the room does not go down.
    mech wrote: »
    You want to seal the window off from the warm air in the room as much as possible using the curtains. The best way would be to rest the bottom of slightly long curtains on the window sill. If there's no window sill, a radiator shelf would seem a good idea (or tucking the curtains behind the radiator, but I don't like doing that as it will reduce the performance of the radiator by interfering with convection up the back of the radiator).

    it won't work, that well. Unless your curtains are made of plastic the cold air will still fall through them, and warm air will be sucked down the gap between the top of the curtain and the wall.
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