|WikiProject Physics||(Rated C-class, Mid-importance)|
- 1 Building insulation
- 2 Wikify
- 3 Cavity Walling
- 4 Cavity wall: Something to know about air and heat transfer in the building envelope...
- 5 What is cavity walling?
- 6 This page will be a work-in-progress for a long time
- 7 Update, 5 Feb 2005
- 8 Requested move
- 9 Isn't this backwards?
- 10 Too much emphasis on construction.
- 11 UFFI
- 12 Thermal insulation
- 13 moisture
- 14 Moved Applications section
- 15 History section?
- 16 Introduction section
- 17 Critical radius is a fallacy
I removed the fact tag where it said that not having enough insulation is using a large amount of energy. The fact tag is not necessary because the fact that insulation exists makes the statement obvious. If you don't think so, try sleeping outside in the winter without a sleeping bag and clothes. Guess what? You will share your excess photons with the air around you until you don't have any left. Then you're dead. The fact that more insulation means more energy savings and that many places could stand more insulation than what they have now, is equally obvious. The statement did not quantify the matter as that would be an enormous task to back up. But I submit that one has but to look at how government in many places is offering tax incentives for becoming energy-wise, which means more efficient appliances (some with more insulation on the inside.....) but also more insulation so that you keep the energy where you want it, instead of heating or cooling things that you have no interest in heating or cooling (which is a waste of energy, needlessly putting more carbon in the air). If the article's statement had quantified the matter, then I could see the need for a fact tag, but the generic statement in there should be quite obviously true.--Achim 22:58, 12 November 2007 (UTC)
Fantastic update done today Sept 28 2006. Couldn't have done better myself. -geniescience.
Please add link to thermal resistance and how to calculate temperature drop across material. Initial material for all entries should be at the 4th grade level followed by more exact definitions at the 8th, 12th and then post doc levels. This will ensure maximum accessibility to the general population. A good source for this entry and thermal conductance is at www.omega.com/temperature/Z/pdf/z119-121.pdf
NOTE these comments now apply to the Building Insulation article, as it was created with the latter 80% of this article. Please move there, as appropriate.
Looks like all the following comments pertain to the NEW building insulation article, and so shoudl be moved there entirely. Will be glad to do so, soon, if no objection. --
This article does not conform to several Wikipedia guidlines, and as such is a prime candidate for Wikification. A short to do list to get started with Wikification:
- Remove or rewrite several sections that read as "how-to"s. Read Wikipedia:What Wikipedia is not
- Remove first- and second-person usage
- Move material, especially the sections on individual types of insulators, to separate articles to reduce the size of the article and bring focus back to a discussion of what thermal insulation is
- Rewrite the introduction section to better reflect the article. Read Wikipedia:Lead_section
- Move information about health effects to another article, and replace it with a single paragraph. The primary point of this article is to examine insulation, not human interaction with insulation
- Reduce the size of the R-values sections. There is already a separate article on R-values, so there is no reason to go into such depth here.
The fact that there is so much that needs fixing does not indicate that this is a bad article—to the contrary, it highlights the ambitious nature of the authors in trying to be a bit too thourough.
Âme Errante 23:11, 30 July 2006 (UTC)
I have started some more re-writing. Today I gave the first few paragraphs a quick bash to get most of the fluff out, but I will get some sensible structure to the article in my next effort. --Slashme 09:02, 27 September 2006 (UTC)
Can anyone explain to me how cavity walling helps to insulate a home by telling me how it stops conduction, convection or radiation of heat and the advantages it has over a solid wall and a wall with a gap but no insulation inside. I just can't get my head arround this for some reason.There are different types of insulation.
Cavity wall: Something to know about air and heat transfer in the building envelope...
Heat transfers from warm to cool, it can occur through: conduction, convection or radiation. Conduction is most effective and faster way of transfer; it is the transfer of heat between two objects in contact. Convection occurs though fluids or gases; a cool fluid in contact with a warm solid will heat up through conduction. Radiation is heat moving through space, directly into a solid object (Sun through the atmosphere heating solids).
So what about buildings?... That’s exactly how heat transfers in a building… Heat will be conducted through radiation (through the windows). Convective heat will be driven in and/or out by openings (drafts). And the rest will be transferred through conduction through the walls, floor, ceiling (the building envelope). All these elements are made of materials that have some resistance to heat transfer. The higher the resistance, the longer it takes to the heat to move through the element. If the elements are solid (bricks, slabs, rocks, etc.), then the heat transfer will occur through conductivity. In order to provide resistance to heat transfer, the element thickness can be increased and this will delay the heat transfer (time lag). Another option is to use a material which is poor heat conductor. Insulation… Air is good insulator (low conductivity). If a wall is built with a cavity gap, heat will have to be transferred through convective air currents (except in the studs, which will be through conduction). This will delay the transfer (comparing with a solid wall), so it is good, but sometimes not good enough as heat have a straight path to be transferred from the warmer layer to cooler layer through the air (by convection) and then will reach the other side of the wall. The air provides slower heat transfer but the problem is that it is a direct path. In order to slow down the air currents by providing “non straight paths” the air gap could be split is various enclosed areas.This is what insulation does, in general these materials are made of materials which are very poor conduction of heat enclosing air gaps. In order to maintain its properties it is important to maintain the air gap by not squashing the material. So Air gap (or small enclosed air gaps) are an effective way of delaying heat transfer comparing with a heavy mass wall (like adobe or concrete wall)...
What is cavity walling?
A wall with an air gap in the middle...
This page will be a work-in-progress for a long time
For anyone referencing the Insulation page, please be aware that there's still much work to do in making the page complete, coherent, grammatically-correct, and well-organized. I'm gradually integrating my own notes into the existing entries, trying not to delete anyone else's entries whenever possible, and trying to organize the topics in a logical way. The page might look somewhat chaotic for a while.
Update, 5 Feb 2005
I've completed and cleaned up the Insulation page to the best of my ability. Can someone knowledgeable see if there are any errors, answer the Lingering Question that I left in the spray foam section, and find out the R-value for Dow Chemical's Great Stuff in the typical R-values per inch section? Thanks. - N3362.
It's a lot of good info. Probably needs an intro above the contents, and probably the second person "you" should be changed to third person or whatever the style guide says. Rtdrury 23:32, 6 February 2006 (UTC)
Thanks, Rtdrury. I agree with you about not using second person "you". Sometimes, it is difficult to stay in active voice, not use second person, AND not sound stilted and phony. I can't stand when people insist on using passive voice, which encourages vague, imprecise writing. I wrote this article while doing research on how to rescue my circa-1939 uninsulated, broken-roofed cottage sitting on top of an underground river in a mountain swamp. I've spent way too much time on this article (as well as Weatherization, Thermal mass, Vapor barrier, Mold, and other associated articles), so I'll leave the grammatical and style fixes for someone else to take on, while I return to fixing my cottage. You'll notice that I left plenty of references at the end of the article for anyone to look further into any topic. I'd love to come back and insert some JPEG images, showing the different types and different manufacturers of rigid panel insulation, for example, but every image I have is copyrighted. I might have to go to a building supply store and take some pics myself with a digital camera, assuming the store owners let me. N3362 01:57, 8 February 2006 (UTC)
Darn good start N3362! I will try to assist by adding some more technical info which is needed. Need: Note about R versus RSI as well.
Isn't this backwards?
Under the typical R-values per inch it says: "Air with no external wind = R-1 (still) to R-5 (with convective currents)." Wouldn't still air have a higher R-value?
Yes, you are correct. Thanks for catching this error! N3362 20:21, 4 April 2006 (UTC)
Too much emphasis on construction.
This page is about thermal insulation, but the term seems be used throughout the article to refer to thermal insulation in construction, a less important aspect of thermal insulation than thermal insulation in clothing or body fat. After a large amount of information regarding thermal insulation in construction, there is a sub heading "insulation in construction", with more information. Please put the lot in a separate article.
I think this section is a little off. From what I understand UFFI is still used in Europe, and was found to harmless in some engineering/toxicology stuides precipitated from a lawsuit filed in Quebec. Classic knee jerk reaciton. Will try to clean this up when I can dig up appropriate sources. --Mf135gas 17:21, 31 July 2006 (UTC)
What is thermal insulation? -- 188.8.131.52 19:09, 9 February 2007 (UTC)
- I modified the text above. I assumed that this was meant to be a question of what thermal insulation is. Unfortunately, the purpose of talk pages is to discuss the article, not the subject. My first suggestion to help you is to read the article. If that does not help, you can try the references. If that does not work, I suggest finding someone knowledgeable about physical science. -- Kjkolb 19:25, 9 February 2007 (UTC)
I'm back after 54 months away. Here is my beef: any use of the word "prevent" causes misunderstanding for millions because they need to be told that insulation only slows down an inevitable process and does not prevent it. There is a normal creep back to this key word, "to prevent", which we must guard against. Insulation does not prevent pipes from freezing and bursting in your houses. Five years ago, I wrote much about insulation in construction and in buildings in order to help people get their minds around this fact, i.e. that insulation does not prevent pipes from freezing. Yes, I could have written more about clothing and other areas where insulation is important. I maintain that "slowing down inevitable heat loss" or "reducing heat transfer rate" is not the same thing as "preventing" it. Please comment. — Preceding unsigned comment added by Geniescience (talk • contribs) 20:05, 28 February 2011 (UTC)
Moved Applications section
I've moved the applications section to the beginning of the article (it makes more sense to have the section on calculating requirements at the end). I've also changed "Factors that compromise insulation" to "Factors influencing performance". My justification for this is twofold - the previous section was empty but for a reference to an article on moisture and it seemed to be regularly vandalized because of the word "moisture". I'm sure that this section could be expanded and improved in the future.School of Stone (talk) 15:22, 15 April 2011 (UTC)
There doesn't seem to be a history section in any of the insulation articles. This being the general article for thermal insulation could be a good place to talk about the historic development of insulation (which I think would provide a greater context to the article). I'll look into writing something and put it up as soon as I can.School of Stone (talk) 15:22, 15 April 2011 (UTC)
Considering there is a Wikipedia article which explains heat transfer is there any objection to the removal of the definition of heat transfer in this article?
Most of the information currently in the introduction is superflous (since it explains in detail things which are explained later on in the article) and I believe the section could be shortened significantly to improve clarity.
Is there a need to explain which are the three best performing insulation materials in the introduction? If this information is to be provided it should be in the main article - not the introduction.
Critical radius is a fallacy
The concept of a critical radius for insulation first came up, AFAIAA, in PROCESS HEAT TRANSFER (p.20) by DQ Kern published in 1950. It was counter-intuitive then, as it is now. You cannot add a resistance in series with another system of resistances and reduce the overall resistance of the system. There were two fundamental problems with Kern's proposal. One is that he ignored the skin temperature at the outside of the insulation, yet heat convective htc is a function of air to skin temperature difference to the power 0.25. Secondly, Kern's calculation for rc = kb/ha only has any significance where the critical radius is extremely small (and therefore standard methods for calculating free convection do not apply), or where free convective heat transfer coefficients are far below what would happen in the real world, or where the conductivity of the insulating material is extremely high relative to the convective htc (i.e., it is not suitable as an insulator). Take a reasonable free convective heat transfer coefficient of 2.25 Btu/h/sqft/degF and a typical conductivity for rock wool of 0.033 and plot 1/k*ln(r/r1) + 1/h/r against r and you will get a logarithmic curve, indicating that, as you add more lagging, the heat loss will decrease, but with diminishing effect, which is as to be expected. You COULD force a kink into the curve, as per Kern, but only by using completely unrealistic values of k or h. To summarize: Kern's theory only holds true for insulating materials that have lower resistance than the convective air that they have displaced - i.e., insulators that are less efficient than free air (!!!) and therefore, for real insulating materials, the concept of a critical radius can be discounted altogether. Hippocrocopig (talk) 19:39, 22 March 2016 (UTC)