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Reflectix still claiming R4.2 for its bubble wrap – my HVAC guy is hooked

richmass62 | Posted in Green Products and Materials on

After reading up a bit on this site, I am worried that my HVAC person is installing the wrong product on the metal ductwork that he is now hooking up. As I understand it, Reflectix bubble wrap might have some benefit in a very hot unconditioned attic where the ducts are carrying cold air. But in my case, the opposite is true: the ducts are carrying hot air only and they are located in a cozy spray foamed attic. Mold formation is not an issue here (the basement is a different story, alas).

My installer is half-done and while the attention to detail is far superior to what the previous installer must have had, I already notice that the ductwork, 20 feet of it, plus the main supply plenums are quite warm to the touch when the system is running.

The Reflectix product has “R 4.2, 6.0 when installed with an airspace” written all over it so I am sure my installer has confidence he is doing the right thing. How can I demonstrate to him that I am not getting R 4 — after he has used like 6 rolls of the stuff already and has 2 more ready to be used to complete the job? I can’t believe that they would be allowed to market the product as r 4.2 if the actually R value is closer to 1.0. Why is there no class action suit?

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  1. HDGFHkB5cP | | #1

    Unfortunately, you are probably getting what your contract specified. Ask how much it would cost to upgrade then sign the change order. Or wait til he's done and redo it yourself.

  2. richmass62 | | #2

    One of the main reasons we did this was to eliminate the problem of the HVAC causing the attic to bake at 80 degrees all winter.

    Our contract specified he would "Seal and insulate all mentioned ducts to an R-4.2 value."

    Isn't the correct R6 duct insulation cheaper than the reflectix that claims r4.2? What is the brand of insulation that others recommend for this application?

  3. GBA Editor
    Martin Holladay | | #3

    Here's an article with more information: Is Bubble Wrap Duct Insulation a Good Idea?.

    Reflectix has a published R-value of R-1.08, so the contractor is probably in violation of the contract unless the duct wrap is being installed over special air spacers.

    Here's what I wrote on the topic in answer to a question posed a few years ago by a reader of Energy Design Update:

    "Reflectix insulation is a 5/16-inch-thick product consisting of bubble-wrap plastic sandwiched between layers of reflective material. Several laboratories have measured its R-value to be less than 1; one such result is reported at a Web page maintained by an insulation manufacturer, Glacier Bay.

    "The manufacturer of Reflectix claims that the product can be installed as a duct wrap resulting in an installation with an R-value of 6. That claim is based on tests performed by the ICC Evaluation Service. However, the R-6 measurement is based on an assembly test, not a material test. The assembly used in the ICC Evaluation Service test includes not just Reflectix bubble wrap, but a site-built 3/4-inch-thick air space. In fact, the reported R-6 derives to a large extent from the air space, not the Reflectix.

    "To create the air space, an HVAC contractor must install 3/4-inch-thick plastic spacer strips every two feet along the length of the ductwork. The spacer configuration is described in the lab report: “Nominally 3/4-inch-thick by 1.5-inch-wide plastic spacers are attached to all four corners of the duct using Reflectix tape, with this assembly repeated every 2 feet along the duct’s length. Reflectix insulation is installed over the spacers and pulled tight to create a 3/4-inch air space. Joints are taped using Reflectix tape.” A Reflectix fact sheet advises, “If the duct is supported with saddle clamps, make sure to install a spacer on the two bottom edges of the duct directly between the clamp and the duct.”

    "Most HVAC contractors are likely to consider the construction of a three-dimensional site-built air space around installed ductwork to be labor-intensive and awkward, especially considering the difficulties of working around hanger straps. Moreover, the R-value of the assembly depends on the long-term maintenance of the 3/4-inch air space; if the Reflectix ever sags, the R-value of the assembly will drop."

  4. richmass62 | | #4

    Martin, I did see the previous articles on Bubble Wrap insulation with your responses. The link you posted is not working btw, but it is available at*/

    Is the test conducted BY REFLECTIX showing the R1.0 performance published anywhere?

    There actually was some action by the FTC in 2009 to bar deceptive insulation claims, which is counter to what glacierbay was saying on their web site. See:

    But clearly there needs to be an orchestrated effort to get the current FTC and the new office of consumer protection (part of the ftc) to enforce misleading R value claims.

    Anyone else out there willing to go to the site and file a complaint?? The reflectix site state that "The product provides an R value of 4.2 when directly installed to the duct." and that is on a pdf they last revised on December 20, 2011:

  5. GBA Editor
    Martin Holladay | | #5

    I have been complaining to the FTC about R-value scam artists for years, and have also complained of the lack of enforcement efforts.

    You should direct your comments on this situation to:
    Hampton Newsome, Division of Enforcement
    Bureau of Consumer Protection
    Federal Trade Commission
    600 Pennsylvania Avenue, N.W.
    Washington, DC 20580
    hnewsome [at] ftc [dot] gov

    I am attaching a lab report by R&D Services, one of the most reputable labs in the country for R-value testing, showing that the R-value of Reflectix is R-1.08.

  6. richmass62 | | #6

    Just got an email from Reflectix with their actual ASTM test results. I am posting it. Please help me interpret this...

  7. GBA Editor
    Martin Holladay | | #7

    I provided you with a document showing the R-value of the material -- basically, R-1.

    The document sent to you by Reflectix shows an assembly R-value, not a material R-value. The assembly tested in that document includes an air space created by the careful installation of spacers used to maintain an air space between the duct and the Reflectix. The results only apply IF your contractor included the spacers, IF the contractor followed the same installation procedure as used in the lab, and IF the Refelctix never sags in the future, diminishing the air space.

  8. richmass62 | | #8

    I talked to a few hvac people and not only haven't they heard about the issues with Reflectix; it is becoming more common among installers. Massachusetts towns are adopting a stronger building code (see which was part of the Green Communities Act, and 2 layers of reflectix are considered by building inspectors to meet the R-8 duct insulation requirements when ductwork is installed in an unconditioned space.

  9. GBA Editor
    Martin Holladay | | #9

    You're right -- code enforcement officials are overwhelmed by the rules they are required to enforce and are therefore being fooled by scam artists and deceptive marketers.

  10. 5C8rvfuWev | | #10

    Rich, in your circumstance I wouldn't be worrying about educating the hvac guy on his materials ... he likely isn't going to be inclined to listen to you. I'd only indicate I was dissatisfied with his selection of materials and prefer he change to what you want. And as was said pay the upcharge. I agree it needs to be fixed and there's no sense going back to deal with it as a repair issue on a new system.

  11. richmass62 | | #11

    Joe -- what product do you recommend? One HVAC guy I spoke to mentioned FSK by Johns Manville -- here is a pic: . I have already told the installer I was willing to pay extra to fix it.

  12. 5C8rvfuWev | | #12

    There's a product guide here on GBA which I use for reference, but probably someone who has actual experience w/the work will show up to answer. Good luck.

  13. richmass62 | | #13

    I called Reflectix today, after hearing nothing for two days when I made my request for test results of the product when used WITHOUT an air space. They put me on with the main engineer who said that he could sent me a test result but he cautioned that "there was no testing apparatus" when they originally did the test so what he sent was a research paper published over 22 years ago (!) by Tennessee Tech.

    Now I can't believe that a 22 year old test would have much relevance, as the product certainly is not completely the same as it was back then, but who knows?

    Here is the link to the document he sent. What do I make of it? It seems to attribute an R value of 1.5 for a duct that is uninsulated, and 4.1 for 1 layer of reflectix. Sounds like two ridiculous claims.

  14. GBA Editor
    Martin Holladay | | #14

    The Google document was prepared by David Yarbrough, whom I often talk with on the phone. I can try to call David tomorrow to clarify these questions.

  15. richmass62 | | #15

    Martin, did you speak with David?

    As for our attic, the Hvac guy agreed to use Knaupf R4.2 insulation for the remaining supply lines, which should make a big difference. When he is done, I will add some additional insulation to the plenums where he was already finished.

    I also should mention that I am very happy to have properly sealed ductwork, at last. It makes a big difference!

  16. richmass62 | | #16

    oops, duplicate post..

  17. GBA Editor
    Martin Holladay | | #17

    I received an e-mail from David Yarbrough on Saturday. It doesn't really answer all of my (or your) questions, but it does explain that the document you linked to is not a standard ASTM test measurement, and is a very old document (1989). To me, it seems like Reflectix is grasping at straws to find a document that they can use to bolster their claims.

    Here's what David Yarbrough wrote: "The document you referenced was a report to Reflectix regarding a research project I did for them while I was at Tennessee Technological University (I retired from TTU about 10 years ago). The test apparatus I built was the first in a series of duct testers. R&D Services now has two later versions (that are Included in our NVLAP scope of accreditation). I can’t imagine how you got a copy of the internal report to Reflectix, although there is nothing wrong with the technical content. The data from the project formed the basis for a “peer reviewed” paper in the Journal of Thermal Insulation, “Thermal Resistance of Air Ducts with Bubblepack Reflective Insulation” Vol 15 pp. 137-152. In the meantime, an ASTM standard has been developed for the testing of reflective duct insulation that follows ASTM C 335. The modern versions of duct insulation from Reflectix have been evaluated at R&D Services using ASTM C 1668."

  18. GBA Editor
    Martin Holladay | | #18

    I just got off the phone with David Yarbrough. Here's what I learned:

    1. The material R-value for Reflectix is, indeed, only R-1.

    2. The advertised R-value of R-4.2 for Reflectix applied directly to a duct is an assembly R-value. The number is inflated by the air film value on the exterior of the product (about R-1.4) plus the value of any air trapped between the Reflectix and the duct.

    3. Ordinary fiberglass duct insulation manufacturers do not use this method of rating or labeling their products. They don't include assembly R-value figures that include the air film; they just include the material R-value. You could inflate the R-value of fiberglass duct insulation in a way similar to the way that Reflectix does, but that is probably illegal.

    4. When you add a second layer or a third layer of Reflectix on top of your first layer, each additional layer gives you an added value of R-1, because that's the R-value of each layer. A value of R-8 for two layers of Reflectix is preposterous.

    5. The honest R-value for Reflectix is R-1.

  19. richmass62 | | #19

    I think it is true that the Reflectix will have a greater than r-1 value in the application of the product directly to a metal , though this is almost by accident. For example, I noticed that the product is warm when wrapped tightly around metal hard duct. However when applied to a large plenum (rectangular wrap) the fit is not as tight and there is more air trapped inside (very tiny leaks, holes for the dampers, sag, etc). However to claim that this is an exact value of "R4.2", when in reality it is an accidental R value of 1.5 to 2, is fraudulent.

  20. GBA Editor
    Martin Holladay | | #20

    I agree with you. Any duct insulation will trap some air between the insulation and the duct, but no manufacturer but Reflectix has ever had the chutzpah to try to claim R-value credit for such factors in its product labeling.

    One big downside to this deceptive labeling is that contractors assume that if one layer performs at R-4, then two layers perform at R-8. Nope.

  21. wjrobinson | | #21

    Interesting info, and great work MH researching/reporting,

  22. BHowe | | #22

    I have been reading your responses to the various situations where the bubble wrap radiant barrier product was being used by HVAC contractors as a duct insulation. I recently had to replace all the duct system in my crawl space due to Sandy flood damage on the eastern shore of Maryland and the new duct system was installed with the 1/2" Reflectix double bubble product installed as an R-8 duct insulation. The installation neglected to include the 3/4" spacers to create the airspace needed for the radiant barrier assembly to work as a duct system insulation assembly effectively. As a BPI Building Analyst & Envelope Professional and HERS Rater, I informed the contractor that the installation was not done correctly. The contractor contacted Reflectix and they told him that the 1/2" double bubble product used with no air space still has an effective R-6 duct insulation value. They are basing this claim on another Test Report done by R & D on August 2, 2011 measuring Thermal Resistance Measurements according to ASTM C1668/C335 on the Reflectix Double Bubble Duct Insulation. As a building science professional and building contractor I am still somewhat skeptical on that claim being made as a result of that single test. Here is a page from the report that describes the testing that was done. I have the whole report but I am still somewhat skeptical about how accurately the results of this test equate to the claimed stand alone R value of R-6 for the Double Bubble product. I spoke to Reflectix and explained my concerns with my fairly extensive new duct system being wrapped with the product and what my options are to get the duct system insulation up to the R-8 insulation value. My HVAC contractor will do what ever is recomended to achieve the minimum R-8 value. One suggestion is to wrap over top of the Double Bubble wrap with conventional foil faced FG duct insulation. The other is remove the bubble wrap and rewrap using new Bubble wrap with the proper installation with 3/4" air space, which would be a nightmare with the duct system already installed, or rewrap using conventional R-8 foil faced FG duct insulation. I asked Reflectix what their recommendation would be and they seemed to indicate not wrapping the Double Bubble with a layer of conventional foil faced FG insulation. I am hoping to get some feedback on the best possible practical solutions to achieve an effective R-8 duct system insulation.

    Page 2 of 5
    P.O. Box 2400
    Cookeville, Tennessee 38502-2400
    Phone: 931-372-8871
    Fax: 931-525-3896
    Thermal Resistance of External Duct Insulation
    R&D Test Number: RD112169DT Date of Test: July 20-29, 2011
    Specimen Number: 1071110622-6 Manufacture Date: Unknown
    Test Method: ASTM C 335, “Standard Test Method for Steady-State
    Heat Transfer Properties of Horizontal Pipe Insulation”
    Report Prepared for: Reflectix, Inc.
    Contact Person: Monty Millspaugh
    Description of Test
    The resistance of externally applied air-handling duct insulation is determined using a calibrated
    end apparatus operated in accordance with ASTM C 335 with analysis in accordance with Section
    10.8 of ASTM C 1668-09. The calibrated end apparatus is discussed in Section 5.4 of the test
    method. The test apparatus is a seven-foot long section of 8 by 12 inch rectangular steel duct.
    An electrical resistance heater is mounted horizontally along the center–line of the duct. Fans at
    each end of the duct provide internal air circulation. Eight Type-E thermocouples are
    permanently attached to the interior surface of the duct to provide a hot-side temperature. Four
    thermocouples are attached to the outside surface of installed duct insulation to provide a coldside
    temperature. Thermocouples are attached to rectangular end caps of known thermal
    resistance in order to determine heat loss from the ends of the apparatus. Two thermocouples are
    placed four inches from the exterior side of the duct insulation to measure the temperature of the
    air adjacent to the insulated duct. The entire apparatus is located in a conditional space that is
    maintained at 70 +/- 2 ºF and 50 +/- 5% relative humidity. R-value for the duct insulation is
    obtained from Equation (1) where the heat flow through the insulation is determined from
    Equation (2). The heat flow through the end caps is calculated from Equation (3) where the Rvalue
    for the end caps is obtained as a function of temperature using a heat-flow meter apparatus
    operated in accordance with ASTM C 518.

  23. GBA Editor
    Martin Holladay | | #23

    I just got off the phone with David Yarbrough at R&D Services. Fortunately, the laws of physics haven't changed since I last spoke to David. Reflectix still has an R-value of R-1.

    The R-6 claim is based on measurements of the R-value of an assembly, not of Reflectix. The assembly R-value included the R-value of the Reflectix, the R-value of a necessary air space between the Reflectix and the duct (maintained by a complicated and unlikely Rube Goldberg contraption of plastic spacers), and the air film on the outside of the Reflectix.

    If Reflectix reps are claiming R-6 for the product alone, they are lying. They are also in violation of the federal R-value Rule.

    More info here:

  24. Expert Member
    Dana Dorsett | | #24

    Assigning an R-value to any low-E material (even low-E windows) is always an error, since the both the assembly and the delta-T affect it's performance dramatically.

    The radiated portion of the heat transfer is proportional to the differences in the fourth powers of the absolute temperatures (degrees Kelvin, or degrees F above absolute zero) of the emitting and receiving surfaces, and the emissivity/absorption fractions of the material types of black-body radiation at those temperatures.

    R-value in an ASTM-C518 test is approximately linear for most materials over a wide range of temperatures and delta-Ts, and even in guarded hot-box tests. But the heat transfer characteristics of high-reflectivity/low emissivity materials are anything BUT linear with temperature, and even with air gaps the spectral absorption & emissivity of the other materials make a difference.

    Without significant air gaps the radiated fraction of the heat transfer is infinitesimally small- it's primarily conducted. With modest air gaps the heat transfer is function of both convection and radiation, and with convection the orientation and width of the cavity for vertical cavities matter, and in horizontal cavities performance will vary dramatically whether the hot side is up vs. the bottom side.

    So tell me what the R-performance is of a duct wrapped in aluminized bubble wrap, with unknown delta-Ts between the wrap and it's local exterior environment, and the delta-T between the duct of unknown emmissivity and the bubble wrap is, really? Beats the HELL out of me! (And I have a physics degree! :-) )

    But it sure isn't R6. It's probably not R1 either. It'll cross both performance levels for some fleeting moments in some configurations, but unless you have consistently high delta-Ts between both the duct, radiant barrier, and whatever radiation-temp of the exterior environment facing the radiant barrier, it's average performance is going to be pretty pathetic, and not worth the money paid to purchase & install it.

    Even attics in Texas don't stay 130F & higher all day long, even on the hottest day of the year, and if they did there might be a bigger argument for never installing ducts in the attic than just insulating the ducts or installing radiant barrier at the rafters.

    Radiant barriers excel at insulating things in outer space though, where all heat transfer is radiant, with a very COLD average radiant sky temps on the shady side, and and extremely high radiation temp on the sunny side. (Remember it's the difference between the FOURTH POWER of the hot and cold side temperatures, which is HUGE in the outer-space case.) So, if you're installing your ducts on the outside of a space station, this is really the right stuff!

    Even if you're installing your ducts outdoors within 20,000' of sea level in locations a lot warmer than Antarctica, or inside of conditioned space anywhere, fuggedaboutdit- it's nearly worthless (or at least not worth what it actually costs.) Average delta-Ts are too small, and other factors will dominate the heat transfer equation.

    Assigning single number U-factors to windows(particularly low-E windows) is a similarly squishy thing, since performance is not linear with temp. And to make it even more fun, the US uses a different standard for the delta-Ts & modeling for assigning a single U-factor than in Europe, just to make converting between performance numbers impossible without using the real-math using the different modeling conventions on the actual window construction. (There is literally no way to make the comparison based on the single number- you have to model the construction using both European and US standards).

    But at least with windows assuming substantial air-gaps on both sides of a window is legit, and the gaps between panes is known, unlike the radiant barrier case. And the fraction of the U-factor from the window framing is somewhat linear over realistic temperature ranges, which complicates but flattens the curve.

    If you flunked Thermodynamics 101 or slept through the parts about heat transfer, read this:,articleId-10428.html

    The heat transfer bits start about 2/3 of the way down the page, or just search the page for "Stefan-Boltzmann" if you want to go straight at the radiated heat transfer portion.

  25. builderkid | | #25

    Sorry to come back to this so many years later. But here in the Bay Area of California I see bubble wrapped ducts everywhere, now. I am the crank who had to special order the right product (R8 fiberglass with fiber reinforced foil facing) while installers I no longer want to hire think its the sh--. We are a state flooded with complex Title 24 regulations and the related paper work and attendant desk jockeys that can't even prevent the most obviously bad practices from happening.

  26. user-5946022 | | #26

    Interesting that this post is just revived today. Today I spent time in my crawl space replacing some equipment, and was quite annoyed with the itchy 12"-18" of fiberglass insulated flex between my equipment and the hard duct. I sat down at the computer to search for non-fiberglass insulated flex. As far as I can tell
    1. For pre-insulated flex, fiberglass is the only option
    2. For field insulating ducts, the only two options are various incarnations of this foil stuff, and some foil faced cotton duct insulation that comes 16" at its widest (an 8" duct has a circumference of over 25", so the only option for using the cotton is to apply it in 16" sections.

    If I were an installer doing this every day, you can bet I would be looking for a product without the itchiness and health issues of fiberglass.

    While the misinformation associated with the foil bubble stuff, and its rampant misuse is unfortunate, the real problem here is that no manufacturers seem to be offering installers a good alternative. It is 2022 - surely there is some sort of foam or other affordable insulation material that could be similarly easy to work with as the foil bubbles.

    I do see that the foil stuff comes in both the bubble variety and one that is a sandwich of foil, foam and foil. I wonder if it's R value is any better?

    1. builderkid | | #28

      Fiberglass is a bit itchy. But prior fears of its safety never turned into strong evidence of it being "the new asbestos." It's not a perfect product, and I would love to see foam and mineral wool equivalents. But the inescapable fact is that it actually resists thermal conduction well, and is a mainstay of sensible, economical, yet highly energy efficient homes. Bubble wrap conducts heat pretty well. It's only value is that its a mirror. The vainest person in the world needs a pretty big air gap between their face and the mirror they stare at or it is useless.

  27. builderkid | | #27

    Not a bad idea to keep some bubble wrap in one's pocket so you don't break a sweat when facing something like this. Otherwise, its R1.0.

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