Foil Radiator Reflectors - are they of benifit?

[martin W]

Hi all, I had a bit of a search and pretty much came up blank on this topic. Has anyone fitted these and do they help at all?

http://www.ecofirst.net/radiator-reflectors.asp

I understand the concept of radiated (infra-red?) heat being reflected back into the room instead of absorbed by the wall, but radiators are white and I thought they did not radiator (infra-red) heat?

So the question is, are they worth fitting behind radiators that are on external cavity insulated walls? Will they reduce the heat losses through the wall and / or conversly save me money on my heating? Simple quesiton really, but the answer is not likely to be

I am soon (ish) going to replace 4 radiators that are on external walls, and it will be easy to fit these sort of thing (or normal foil stuff) when the new rads go in.

[Amy]

yes they are a benefit

radiator are mis named as they dont radiate
they convect.
the warm air rises above the rad, travels across the ceiling untill it either cools enough to fall or it hits the opposite wall and then falls, so you find the warmth of the rad is best felt at the opposite end of the room.

The rad reflector panels i used to sell had an undulating surface that caused a disturbance to the convected airflow, which caused it to turbulate and fall to a lower level sooner, making the room more evenly temperate

[David]

So the question is, are they worth fitting behind radiators that are on external cavity insulated walls? Will they reduce the heat losses through the wall and / or conversly save me money on my heating?

Yes. Yes. The answer to the last bit is that they will save a small amount of money which will add up over the years. However, to save larger amounts of money look at loft insulation and then the walls (I couldn't make out whether the cavity walls are insulated or not).

[Ivan]

I've got quite a number of thermal images which quite clearly show the position of radiators from the thermal emission from the exterior wall 

[dhaslam]

Quite a lot of heat from radiators is radiation but of course single panel radiators without fins are best for radiant heat.    Radiant heat means that less air temperature is needed for comfort but the  efficiency saving may be offset by half of the radiant heat being output to the wall behind and some heat will be lost, even with reflectors.      

[sleepybubble]

they're so cheap its got to be worth a shot!   

[martin W]

thanks for all the positive replies.. I thought they would be of use.. but was wary of hens teeth.

David, walls just had the cavities filled and loft has between 200 and 400mm of insulation (some areas have 400mm some as of yet havent been double insulated).


If the radiators where of the same size would a single panel radiate less heat to the wall than a double panel (I know the doulbe rad will have close to double the heat output to the room). I am sort of asking which is more effcient at room heating, or les wastefull in heating the wall..

Ta.

[guydewdney]

I've got quite a number of thermal images which quite clearly show the position of radiators from the thermal emission from the exterior wall 

not on my house you aint

Whilst I agree in priciple to the above comments - I have to chime in with the old 'thermal mass' argument - my house has 2+ foot thick walls of nearly solid rock. Get that up to temp, and it stays warm for ages (and takes ages to re-heat ) and in a place mile mine - heating a wall is a bit like heating a night storage heater.

You can keep yer poncey plasterboard and fluff walls 

[Amy]

they're so cheap its got to be worth a shot!   

Have you seen the price of condoms?

I wouldnt call them cheap at all, ..........more of a rip off. 

[desperate]

Amy Hi
If radiators dont radiate whats the good of a reflector? youseem to be talking about a baffle, or am I baffled   

Desp

[sleepybubble]

they're so cheap its got to be worth a shot!   

Have you seen the price of condoms?

I wouldnt call them cheap at all, ..........more of a rip off. 

erm the price of condoms doesn't seem to have changed much in 20 years. Its 3 for £1 from the machine in the pub bog isn't it?
How that relates to the foil reflectors you put behind radiators I'm not so sure, er?

[oliver90owner]

Ten quid a radiator, to try it, seems very expensive.  For much less - as in sheet of alcan foil, shiny side out, stuck to a insulating panel and screwed to the wall - would be just as effective , especially if another couple of sheets of foil were stuck to the back of the cheepy panel on the wall side with an air-gap between the panel and wall.  The 'ten' packs seem very much closer to a reasonable price.

As some have indicated, not much use where rads are on internal walls.....

Regards, RAB

[martin W]

Well I sort of thought about some foil backed kingspan stuff, but I don't think you can get it around 15mm thick. The thing I liked about the item in the link, was that the corrigations look like they distrupt the airflow and stop it going staright up to the ceiling.

If I could sourch good thick foil, and a reasonible insulation board (10mm max thickness) I would probably make my own. I dont like the stuff you buy on a roll from B&Q et al, I prefer a solid rigid panel as it doesnt try to curl up again on the wall.

Oh and all the rads will be on external walls under wndows. I know its not the best location, but its the most practical in these rooms.

[martin W]

Whilst I agree in priciple to the above comments - I have to chime in with the old 'thermal mass' argument - my house has 2+ foot thick walls of nearly solid rock. Get that up to temp, and it stays warm for ages (and takes ages to re-heat ) and in a place mile mine - heating a wall is a bit like heating a night storage heater.

You can keep yer poncey plasterboard and fluff walls 

I saw a additive which you can add to paint which stops / reduces the thermal losses though the wall . It is mentioned on here somewhere, maybe you should loook at it to stop ur walls action like a big radiater and heating up the outside 

[Richard Owen]

Radiators will provide heat to a room by both radiation and convection. Let's call them emitters to distinguish them from the type of energy transfer.

Radiation increases by the square of the temperature, so the lower the temperature of the emitter, proportionally more heat is transferred by convection than radiation.

One confusing factor in all this is that human skin is more sensitive to radiated heat than it is to conducted or convected heat. We feel warmer from radiation than convection or conduction. What Amy points out about the warm area of a room being on the opposite side from the emitter is correct, except that for hot emitters, it may not feel like that. It may feel warmer next to the emitter. Even though it isn't.

A single panel, unfinned emitter will have the largest surface area (just under 50%) facing onto a wall and therefore have the largest heating effect on that wall. Fins on the back of a radiator will create a larger heating surface, move more air through by convection and are therefore a lower temperature and therefore proportionally less energy is transmitted to the wall via radiation. Double emitters will have only 25% of their emitting surface facing a wall and double finned, double radiators will have the lowest radiated energy and therefore exhibit the lowest amount of wall heating.

I would have thought that the most effective way to avoid heating the walls would be the thin, foam insulant, foiled on both sides, mounted with an air gap on both sides, between the emitter and the wall.

What I don't know is the effect of your cavity wall insulation on the whole affair. It may be worth sending £50 Ivan's way in the heating season to have some thermal images done of the house to see how leaky it is. If you can't see the emitters through the wall on the thermal images because of the effect of the cavity insulation, then there's no point bothering with the foil stuff.