Silver foil behind radiators worth it?

mech_2

Cardew wrote: »

No they do nothing - otherwise we would line the whole room with silver foil.

I've seen a whole wall lined with foil. It was a begger to get it all off.

The area behind the radiator(eg behind the silver paper) will get just as warm as the rest of the wall by conduction.

e.g. half submerge a house brick in a bowl of water, and the whole brick will reach the same temperature.

I'm not sure what you're trying to demonstrate here, but I don't think it's true. If bricks conducted heat that well/quickly the inside of a solid wall would be the same temperature as on the outside of the house and I know that isn't the case.

davholla

stevehead wrote: »

If silver foil was any use as an insulator then you wouldn't be able to roast your turkey in it - the bird would be raw yes?
There is a similar looking material called Mylar which is a very very good insulator. (reflector)
You often see mountain rescue victims wrapped in the stuff, and indoor cannabis farmers use it to mask the heat signature from the loft!
Mylar 'might' (because it could) make a difference behind a radiator, but on an outside wall only.

In an oven the bird is heated by convection. Radiators heat by radiating heat the theory about foil is that it reflects this back into the building.

Therefore your analogy about the turkey is not very useful. The theory behind silver foil seems to make sense whether it is actually worth the effort or not is debatable.

samtheman1k

I assuming the OP means foam backed foil, rather than just foil. Simple physics says it does work as foam is a worse conductor than bricks.

richardc1983

stevehead wrote: »

indoor cannabis farmers use it to mask the heat signature from the loft!
.

Trying to tell us something Steve?

Hadrian

davholla wrote: »

If I put silver foil behind the radiators does it really make the house warmer?

It is possible to buy 'silvered' bubble wrap. That with 1cm thick polystyrene sheets should do the job. Get 250mm loft insulation AND wall insulation (or whatever that's called) should make a h*ll of a difference. It has with me and everyone notices. Also keep the heating on (LOW= 16c) all day when frosty, if you don't all the heat migrates to the walls and when you 'fire up' the heating the first lot goes to heat up the walls. Draught proof the curtains/doors and wear thick a 'wooly pully'. One more that I worked out was vacuum when the room is cold, mine throws out 2500 watts! Doing all that, according to my gas/elec supplier has lowered my gas consumption by 53% over 2008 consumption. One more thing, I am astonished at the profligacy of many of my friends/relations with their gas/elec. Same house as their's = 40%+ more than me. It can be done, try!

cliffski

The answer to the original question is:

YES.

I was doubtful about this too, and joked to my missus (a scientist) that it's not worth doing unless she can provide me with 'peer-reviewed science' that proved the case. She found a paper on it a few hours later

Even forgetting the science, we have managed to gather our own evidence for this. We put it behind all our external wall radiators, and as a bit of an insulation geek, I have an infa-red thermometer. You can tell the difference by measuring the external wall temperature when a radiator is on, with and without foil behind it.

The foil itself is pretty cheap (we bought a roll from B&Q and got a free 2nd roll with it, which we used to double-lag our heating pipes in the cellar. It only takes an evening at most to measure and cut the stuff and tape it to the wall discretely behind the external-wall radiators.
It's maybe one of the cheapest and easiets things you can do in terms of insulation that makes a direct difference.

pm1961

Of little use at all I'm afraid........ Intuitively it sounds like a good idea but doesn't really stand much close inspection and is never backed up with facts.

If you've done absolutely everthing else then maybe, but I still think the effect is more placebo than anything else.

Radiators heat by radiating heat

Only partly true I'm afraid...... every hot object "radiates." What we call a radiator relies mostly on convection and less so on radiation. It's probably the most inappropriate name for a device ever......

Stick your hand 1m in front of a rad....... how much heat can you feel?..... a little maybe?

Stick your hand 1m above a rad........ feels much hotter.... Warm air by convection... the main mode of room heating.

If bricks conducted heat that well/quickly the inside of a solid wall would be the same temperature as on the outside of the house and I know that isn't the case.

Not true I'm afraid.....there will always be a temperature gradient across the brick unless the outside temp is the same as the inside temp.

Stick a metal spoon and a brick in a pan and boil the water....... they all get to 100C eventually..... it just takes the brick longer because of the rate at which they conduct heat...... take 'em out and stick them on your worktop..... the spoon will cool down PDQ, the brick will be warm for ages.......

Besides, that is just a theoretical case..... we are mainly talking about cavity walls with or without insulation in them. The only saving would be, as a previous poster said, the miniscule amount of insulation that it adds to that tiny portion of wall. Plus, a tiny amount of radiated heat which is reflected back to the radiator.

Thats why they wrap runners in space blankets

because they are windproof and reduce heatloss by evaporation. The human body is also quite an effective radiator, so in this case it is more appropriate. Just sitting in a chair a body pushes out around 100W. Fill a room with people and the temp soon goes up...

They (the people trying to sell you something) mess with the science and your head. Their claims might have a grain of science "fact" in them, but that doesn't make them cost effective or worthwhile.

Ask British Gas for the science paper on which the £19 saving is based.... I bet they don't reply with one!

mutley74

my dad got some special radiatior reflectors from the council which had a grant to give oaps this. Not the easiest to stick on as the double side tape that comes with it just dries up, so i need to use a staple gun.

shandypants5

pm1961 wrote: »

They (the people trying to sell you something) mess with the science and your head. Their claims might have a grain of science "fact" in them, but that doesn't make them cost effective or worthwhile.

So why ARE space blankets silver?

I know you are trying to convince us that silver foil make no difference, but have you tried it?

It easy to test, wrap some card in foil and slide it behind a single rad.
If you have a long rad you can just do half of it.

Then get someone to hold their hand in front of the 2 halves and tell you where feels hotter. (you can blindfold them for fun if you like).

I have tried it and I could feel a difference in temp.

Try it yourselves.... what have you got to loose.

I may have to borrow the inared sensor from work and post some facts up here for the scientists.:rolleyes:


Oh yeah just one thing, how does a thermos flask work?... and why do they make them "silver" on the inside?

theduchesshavoc

So... Will this project work if you cover cardboard with aluminum foil and stick it behind the radiator, rather than forking out for the insulation foil?