Wikiaccuracy?
user-757117
| Posted in Energy Efficiency and Durability on
I was nosing around on wikipedia and I came across the statement below regarding radiant barriers in wall assemblies.
http://en.wikipedia.org/wiki/Radiant_barrier
I’m skeptical…
Can anybody verify that “wrapping a house with radiant barrier” can produce such results?
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Replies
Lucas,
You have come up with an excellent example of why Wikipedia is a useless reference work. The articles on R-value, emissivity, and radiant barriers have been battlegrounds for years. In the early years, I tried to correct these errors, but my corrections were quickly removed by scam artists and people peddling questionable products like radiant barriers.
I threw in the towel and gave up.
In the citation you have highlighted, there is a footnote. The footnote is a link to a commercial website -- a distributor of radiant barriers! Is this link a footnote or a type of marketing?
When I was in high school, I was taught that footnotes were for citing academic papers...
From Wikipedia... "Wikipedia, the free encyclopedia that anyone can edit." Sounds more like it was edited by a radiant barrier salesmen.
Martin,
I noticed the footnote as well...
Like you I believe citations should be reserved to reference supporting academic work.
I think wikipedia is very much like most media sources...
Very little can be taken at face value.
It is important to do more than just scratch at the surface these days.
That's one thing I've always liked about the GBA Q&A...
Critical thinking is not discouraged.
Boys, I like you all and I like Wikipedia. I found no misinformation and no edit-(misleading) "results" reported either.
EDIT...
OK... I read past the savings blah blah and don't have an issue with it. The article does say that warm climate use is where radiant barriers have there best performance. Seems that is what has been said by many. I still think the page is written well. You guys act like those that don't believe we have rocketed into orbit. And the R value page looks quite useful too. (end of edit)
But also, I am not advocating the use of radiant barriers in the Adirondacks either and don't.
I am glad Wikipedia exists along with many of the other Wiki's.
Just clicked to the Thermal radiation page.... http://en.wikipedia.org/wiki/Thermal_radiation
"Using the formulas below shows a human, having roughly 2 square meter in surface area, and a temperature of about 307 K, continuously radiates approximately 1000 watts. However, if people are indoors, surrounded by surfaces at 296 K, they receive back about 900 watts from the wall, ceiling, and other surroundings, so the net loss is only about 100 watts. These heat transfer estimates are highly dependent on extrinsic variables, such as wearing clothes, i.e. decreasing total thermal circuit conductivity, therefore reducing total output heat flux. Only truly gray systems (relative equivalent emissivity/absorptivity and no directional transmissivity dependence in all control volume bodies considered) can achieve reasonable steady-state heat flux estimates through the Stefan-Boltzmann law. "
just a snip... but I haven't read (that I can recall) any of you explaining thermal radiation better or differently than Wikipedia. This site is great here at GBA. So is Wikipedia. And so is BSC for that matter. I recomend all of them.
Just saying and agreeing to disagree as to this thread.
Speaking strictly to the portion on window LowE coatings...that might the most innaccurate description of the process that I have ever seen online or anywhere else.
AJ,
You are free to agree to disagree...
But I think you misunderstand my point...
I'm not suggesting that people should NOT use wikipedia.
I am suggesting that wikipedia is NOT special as a media outlet.
The information needs to be verified before it can be taken as fact.
This true for ALL media...
ESPECIALLY with election campaigns firing up...
https://www.youtube.com/watch?v=EOK7ZjvhgDg
https://www.youtube.com/watch?v=OW-NadlTFIA
https://www.youtube.com/watch?v=2AAa0gd7ClM
sorry a little off topic
Greg, I clipped this from Wikipedia. Please let us know where they are so completely inaccurate.
Window glass is by nature highly thermal emissive as indicated in the table above. To improve thermal efficiency (insulation properties) thin film coatings are applied to the raw soda-lime glass. There are two primary methods in use: Pyrolytic
CVD and Magnetron Sputtering [2][3] . The first involves deposition of fluorinated tin oxide (SnO2:F see Tin dioxide uses) at high temperatures. Pyrolytic coatings are usually applied at the Float glass plant when the glass is manufactured. The second involves depositing thin silver layer(s) with antireflection layers. Magnetron sputtering uses large vacuum chambers with multiple deposition chambers depositing 5 to 10 or more layers in succession. Silver based films are environmentally unstable and must be enclosed in an Insulated glazing or Insulated Glass Unit (IGU) to maintain their properties over time. Specially designed coatings, are applied to one or more surfaces of insulated glass. These coatings reflect radiant infrared energy, thus tending to keep radiant heat on the same side of the glass from which it originated, while letting visible light pass. This results in more efficient windows because radiant heat originating from indoors in winter is reflected back inside, while infrared heat radiation from the sun during summer is reflected away, keeping it cooler inside.
Glass can be made with differing thermal emissivities, but this is not used for windows. Certain properties such as the iron content may be controlled changing the thermal emissivity properties of glass. This is "naturally" low thermal emissivity, found in some formulations of borosilicate or Pyrex. Naturally low-e glass does not have the property of reflecting NIR/thermal radiation, instead this type of glass has higher NIR transmission leading to undesirable heat loss (or gain) in a building window."
"
I don't know much about glazing ...
but I am sure that Greg Smith (Oberon) knows what he is talking about
John, would love to have Greg rewrite the above posting correctly. Can't do much with your post.
https://www.youtube.com/watch?v=yghFBt-fXmw&feature=youtube_gdata_player
Greg is right. The "Window Treatments" section of the "Radiant Barrier" article totally ignores pyrolytic (hard coat) low-e coatings. ("Since the thin coatings are fragile, and can be damaged when exposed to air and moisture, manufacturers typically use multiple pane windows.")
;)
I see in with the new year are the minus helpful rewards being liberally tossed! LOL
Cute Brooks and company...
AJ,
The information that you posted from wikipedia on LowE coatings is actually pretty good. My comment was based on the link provided in the original post. In that link there is a paragraph titled "Window Treatements" and if you go to that link and compare it with what you posted you will see what I mean.