Putting foil behind radiators .. Is it worth it ?

Leon_W

There used to be a train of thought that radiators were always mounted under windows which I could never really understand. I appreciate it was sometimes because it freed up other walls for shelves and wardrobes etc but is it the most efficient place to mount a rad ? I genuinely don't know.


Over the last few years when I have redecorated I have taken the opportunity to resite rads on internal walls and am under the impression that my rooms now feel warmer.


Is this psychological or am I right ?

bryanb

jhs14 wrote: »

As radiators work by convection not radiation,

Why are they called radiators then? Surely convectors would be an appropriate name?

saveallmymoney

I have a thermal camera and am a bit of a nut for looking around at where heat is going.

On non-insulated cavity or solid outside walls its worth putting the foil on, if you have cavity wall insulation no significant heat is being lost.

cyclonebri1

bryanb wrote: »

Why are they called radiators then? Surely convectors would be an appropriate name?

JHS is absolutely right, they do work by convection which relies on air current to "spread" heat across the room.
This falls in nicely with the point about rads under windows
Although they will create their own currents in still air eventually, under a window you already have an air current, air is cooled quicker by contact with windows normally and cold air is falling at that point.
Switch the rad under the window on and that existing current is heated and therefor rises across the room before again cooling against the window.


And I really have no idea why they aren't called cons rather than rads, but maybe there's a clue in that sentence

PheoUK

cyclonebri1 wrote: »

Attaching direct to a flat panel rad will actually save money by making the rad output less, therefore the water returns hotter, it won't give more heat into the room it will give less.
However treating the wall behind does give results and directs heat more into the room rather than the wall itself, maybe the freebie matts where spaced of the rad.

Free matts, free light bulbs and free kettles etc?, I'd keep that quiet as most folks have to pay and can get quite "tetchy" when others don't

Except condensing boilers need the return temp to be 55-60c, so by increasing the return temp, you shift the boiler into non-condensing mode, therefore making it less efficient.

[Deleted User]

enfield_freddy wrote: »

no they stop the heat going out of the back and into the external walls , all the heat comes out of the front (in theory)

No, they're supposed to stop heat radiating into the wall without stopping air convecting off the back of the radiator.

Pennylane wrote: »

We did this to all our radiators when we moved in about 20 years ago and the house is always toasty warm.

So the radstats are not doing much, then?

cyclonebri1 wrote: »

Attaching direct to a flat panel rad will actually save money by making the rad output less, therefore the water returns hotter, it won't give more heat into the room it will give less.

Yes, but only to the extent that the radstats don't offset the reduction in rad efficiency.

Leon_W wrote: »

There used to be a train of thought that radiators were always mounted under windows which I could never really understand.

If you don't put the radiator under the window you get cold air falling off the window and drawn across the floor by the radiator on the opposite wall. The radiator in my lounge is under the window, but there's a French window in the dining room so the rad goes opposite. You can feel the difference, but the effect is less pronounced with double glazing.

bryanb wrote: »

Why are they called radiators then? Surely convectors would be an appropriate name?

Radiation accounts for about two thirds of the heat from a surface, but the front of the radiator is the only surface facing into the room. Convection takes place from the front, the rear, and all the fins in between, which means that the area convecting is about 12 times the area radiating. So that would be about 86% convection, 14% radiant.

bryanb

jack_pott wrote: »

Radiation accounts for about two thirds of the heat from a surface, but the front of the radiator is the only surface facing into the room. Convection takes place from the front, the rear, and all the fins in between, which means that the area convecting is about 12 times the area radiating. So that would be about 86% convection, 14% radiant.

So there is no radiation from the back of the rads? or the fins? Sorry but I can't understand your logic.