Talk:Radiant barrier

Currently reflective insulation redirects to the radiant barrier page. Actually radiant barrier and reflective insulation are two different things. The RIMA International handbook shows the differences between reflective insulation and radiant barrier products.

There should be another page specifically for reflective insulation. 69.15.27.150 (talk) 21:27, 26 September 2011 (UTC) CW

Dust when placed on attic floor
There is some reduction in reflectivity, usually no more than twenty percent. If you're using a 97% efficient material this leaves about 80% efficiency. This is considerably more than the approximate 5-10% efficiency of fiberglass and cellulose and about 20% for foam.

If a 100 lb Kraft paper product with foil both sides is used then the radiant barrier will "ride" the peaks of the insulation,thus allowing for some airspace between the foil and fiberglass. It must also be kept in mind that fiber type insulations are about 99% airspace. The surface facing the insulation will not be affected by dust.

A two layer material can be constructed using the 100 lb Kraft/foil material and this configuration will make the dust question baseless. Materials over existing insulation must be perforated, and not stapled down.

--Rbisys (talk), thirty year radiant barrier supplier and installer.

Good points. Sections should be added that break out each type (paint, rafters, decking, on top of insulation, etc) and lists the pros/cons, how to install, etc. Also, what is 100lb Kraft, a brand name? --KarenJo90 01:57, 10 May 2007 (UTC)

Moisture
A section should be added for moisture condensation. KarenJo90 01:57, 10 May 2007 (UTC)
 * Isn't this "not in the tone of an encyclopedia article?" I've seen this header before, and I think this one qualifies. does anyone do this often enough to know?

Thanks. —Preceding unsigned comment added by 128.173.39.115 (talk) 06:05, 11 September 2007 (UTC)

Facing open space
There was wording about facing open space. It was changed to saying that the barrier shouldn't be in contact with the radiation source, because otherwise heat would conduct out. I changed it back. My reasoning is that if someone is worried about thermal radiation from, say, a hot parking lot outside a building, they might put a radiant barrier layer between plywood and foam insulation in a wall assembly, with no airspace. That would do nothing. With a gap between the plywood and the insulation, a radiant barrier in that space could help. Technically, in that case, the outer layer (plywood, perhaps) is the source of thermal radiation, so not being in contact with that source takes care of it. But if people are thinking of the parking lot as the source, they might think that the sandwich with no airspace was OK. Also, if the barrier is in contact with the plywood, that OK, because it stops radiation from that surface. It's only being in contact with both (no air gap) that is a problem.Ccrrccrr (talk) 04:23, 2 December 2008 (UTC)


 * I wish i could see this subject been treated properly from the physics point of view. I can see that radiation needs to be able to propagate to contribute to heat propagation, meaning the waves cannot be evanescent, an index of refraction imaginary part issue, but I can also see a problem of "impedance matching" with the index of refraction real part affecting wave reflection. Radiation and conduction are very different effect: radiation conduction is independent from the gap thickness for distances long compared with the radiation wavelength, while conduction is proportional, but it depends on the index of refraction gradient length. It's all clear in principle, I just don't see how it plays out in practice with realistic numbers, there must be an article somewhere which deals with these issues rigorously enough, doe anybody know where? Oscar Blauman 15:20, 9 August 2023 (UTC) — Preceding unsigned comment added by Omblauman (talk • contribs)

NASA date
The date of NASA invention of metalized film radiant barrier was listed as 1964, and was changed, without a source listed, to 1954. I found this which says is was developed for Apollo:. That would probably put it in the 1961 to 1967 time frame. Anyone have a source? Absent a source, we could make it more vague, and just say "for Apollo", following this source.Ccrrccrr (talk) 00:12, 16 July 2009 (UTC)

contemporary windows
I'm pleased the Radiant barrier item exists on wikipedia. Having no time to edit it now, I just stress that its most important current application, other than in Dewar bottles, is inside the sealed window multi-panes: the almost invisible low-e coatings. Another application could be aluminised foils as movable parts of windows, see ev. my poster from 2005 or an English abstract< of my PhD thesis (the thesis is in Czech, sorry). The other problem is that the term is a misnomer, as regards heat transfer applications. E.g., any glass is a radiant barrier for longwave infrared -- no such radiation can pass through it. But it is not a good mirror for LWIR. A stuff with low emittance can almost stop radiative heat transfer, not just halve it like a single layer of glass/cardboard/plywood etc. Last, emissivity and emittance are different quantities. Emissivity concerns bulk homogeneous material with a polished surface and zero transmittance. Emittance concerns real things of various thicknesses, surface roughness, number of layers. Even emittance of thick non-polished layers is always larger than the emissivity of their material itself (real aluminium surfaces have larger emittance than pure polished aluminium). Emittance is what is important in everyday life. Fortunately, it is the same as emissivity for plain glass. Similarly for reflectance. —Preceding unsigned comment added by Jenikhollan (talk • contribs) 13:54, 11 October 2010 (UTC)