Being in the process of replacing all my 40 year old radiators, I'm wondering if there is any real benefit it putting reflective aluminium foil behind them. And if so, is there any particular product that people would recommend?
Keith
Not a great deal.
Insulation is probably a better thing to put behind them.
Being in the process of replacing all my radiators, I'm wondering if there is any point putting heat reflective aluminium foil behind them. If so, is there any particular brand pople would recommend?
Sorry if this posts twice - I posted it once then it disappeared so I thought I'd better post it again.
TIA
Keith
I'm assuming they *are* on an outside wall? (sorry - just checking!)
I found the thin silvered foam "good" in the sense that that bit of wall didn't need heating, nor did it need to cool any air and the less I felt it was the better.
Not sure how much of a qualitative difference it made.
Ooops - I meant "..how much of a quantitative.."
Quite right to check. My mother was offered various energy efficiency enhancments (due to her status as an 'old dear' :-) ) - and they fitted it behind just about every radiator. I think only two are on outside walls.
Not sure that you can get it thin enough, but I suspect the ideal thing would be to insert a half inch sheet of Celotex in place of the plaster, within the area between the mounting brackets and to within an inch or so of the positions of the top and bottom of the radiator. Could leave the foil exposed too.
Reflective foil would only help with radiant heat such as an electric fire that gives out infra-red, not with central heating since a radiator works by convection rather than radiation, heating the adjacant air directly. So reflective foil wouldn't help significantly. Foam/polysterine/cavity/ type insulation would help. Andrew Gabrial's celotex suggestion is a good idea.
Tony
It'll reduce heat losses by radiation. If you run your radiators at a few hundred degress, then this may be useful. As you won't be, it isn't.
Any thin insulator for conducted heat is useful: bubblewrap, thin foam sheets. Even better is simply to wathc out for convective airflow upwards and not to mount radiatiors directly underneath windows, with a curtain draped over both.
I'm sure when I did the calculations as part of my degree (ages ago) having the warm air current across the inside of the windows had an overall beneficial effect compared to having radiators on inside walls.
Having a curtain over both is definitely a bad idea, though. A radiator shelf to deflect the current more into the room and curtains that hang above the shelf should work OK.
So how does that work?
I'm sure it "worked" but qualitatively, not quantitatively. In the days of mostly single glazed windows, the air cooled by the windows would fall to and along the floor, being perceived as a cold draught on their legs by the occupants. This would be exacerbated by a radiator somewhere else as a circulation system driven by the combination of hot radiator and cold window would form (as had been the case already with open fires). Putting the radiator under the window made no difference to the average temperature but reduced cold draughts and therefore increased comfort (there is also the reason that the wall under a window is often dead space and therefore a good place to put a radiator).
With double glazing, this effect is much reduced but the habit of putting radiators under windows persists. The added benefit of having radiators back to back on internal walls, with the associated reduction in piping, is an added bonus for double glazed homes.
Although the vast majority of heat output from a radiator is convection, there is (a) some radiation and (b) the convection currents behind the radiator will warm the wall. On balance, if I had everything stripped off, I would fit silvered thin foam insulation behind external wall radiators (especially if the wall is solid).
I would fit foil coated foam. The foil makes sod all difference to the heat losses but its a lot easier to clean than the foam.
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