Talk:Radiator reflector

Radiation or conduction?

This needs addressing (refs too). These things are called "radiators" and the foil is described as a "reflector", as if it's about reflecting radiated heat. Yet the numbers just don't work out for this - domestic heating is low temperature, thus ineffective as a radiator (Stefan Boltzmann's 4th power law). In reality, it's about convection instead. So do "reflectors" work at all? If they do, is that due to reflection or due to a reduction in conducted heat loss through the wall. Andy Dingley (talk) 08:25, 14 November 2009 (UTC)

You're right to raise this. From experience it is a combination of reflection of radiant heat, and a reduction in conduction from heated air as well. However, I'll try to find a more specific reference before editing further. —Preceding unsigned comment added by Gareth.randall (talk • contribs) 19:40, 14 November 2009 (UTC)

I too think radiation is a lesser but far from insignificant part of the transfer of heat to the wall and that a reflector would be useful in reducing the heat loss. [1] is “original research” so not encyclopedia material - I'd like to see information from a citable source on whether or not reflectors work. I'm thinking experiments with temperature sensors behind two pieces of otherwise identical reflective material, one of which having had a thin coat of matt black paint added. --EdDavies (talk) 09:06, 14 August 2014 (UTC)

Reading around (see the Harris reference), I deduce that convection is the most important way a radiator contributes to a room's heat, but that radiation towards the wall is a significant contribution towards the heat lost from the radiator through the exterior walls. I think the paragraphs in this article that say that the radiative output from a radiator are negligible are hence misleading and should be removed. Harris does the maths for a parallel plate version of the Stefan Boltzmann equation and has a graph that shows that for radiator temp.=50C, wall temp.=20C, and emissivities of 0.9 (ie not foil) the radiant flux is about 160W/sq. m. Pgj98r (talk) 21:42, 3 March 2018 (UTC)

The content added here looks like the sadly typical WP practice of Googling for text matches in publicly accessible content (published abstracts) without reading the body of the paper. Neither of these papers add much useful content to this article.

The trouble is that neither paper is impressive. They both give the same conclusion, "reflector foils are useful" except that we already knew that, and it can be rephrased as "fuel is expensive, foils are cheap, might as well do it anyway." They do not clarify what the mechanism of this saving is: are they reducing conduction or are they increasing reflectance? There's a failure in experimental design here: there's no control of their conductivity into the wall, no control experiment with an additional radiation barrier, no control with the same foil and an absorbing coating. So what do these actually add to the article here? They certainly don't clean up the question of "Is radiation and reflectance significant?" and they failed to even look at the issue of "Is conductivity from the adhesive layer more significant than the foil itself?"

There's a large push at present for building insulation with "space blankets", multiple layer metallised foils of minimal thickness. They're available, they're convenient, they're expensive, but do they actually work? It's useful to explain these, and where they might or might not be useful, but I don't see the changed article today as doing anything to address either radiator reflectors or thin multilayer insulation blankets. Andy Dingley (talk) 22:57, 3 March 2018 (UTC)

Having read both papers in full, I can confirm that their abstracts are a fair summary of their results. I think the contribution made by citing these two is to a) establish that there is a body of evidence to support that the foils actually have a positive effect (the original article was sorely lacking any decent references at all), b) give rough indications of how big the effect is, c) cite evidence that home-made solutions are likely to be effective (in the face of a lot of hype by manufacturers to the contrary), and d) establish the the mechanism of the effect is indeed through the reflection of infra-red radiation that would otherwise have reached the wall and caused additional heat to escape (the second paper is pure modelling [I will do an edit to bring out this more clearly], and shows this effect is sufficient to account for the phenomena observed). My impression is that there is academic consensus that [single layer] foils do indeed act primarily as a radiant barrier. If not, can some references be found that argue differently? I think I follow your objection about the controls, but I can't think of any plausible physical explanation for the reduction in observed heat loss other than that put forward.

I agree that references to works that have more in depth analysis of more more complex multilayer systems would also be useful, but I think the above points are useful first. Perhaps you have the time to find such references and discuss them. I notice that papers exist in this area for floor and ceiling insulation systems based on the same principle.Pgj98r (talk) 20:08, 4 March 2018 (UTC)

U values

This needs an addition for U values, comparing those measured for Radflek in the two referenced reports with expanded polystyrene or polyethylene foams, and also against typical values and current building regulation standards for new walls. Andy Dingley (talk) 00:51, 22 April 2010 (UTC)

Very odd article

Basically, the article says that they are basically pointless and then we have an ad for the company Radflek. Total crap — Preceding unsigned comment added by 136.173.162.144 (talk) 12:29, 10 October 2012 (UTC)

So fix it. -- Trevj (talk) 21:27, 6 June 2013 (UTC)

radiative loss

modern insulation may not have a radiation barrier. As condition is reduced this becomes increasingly important . 82.39.179.127 (talk) 06:23, 5 January 2024 (UTC)