1 Helpful?

Is bubble wrap duct insulation Energy Star approved, and is it a good idea?

I spoke with a HVAC installer who said he wanted to insulate my ducts with double-wrapped bubble wrap as a cheaper way to achieve R6. Does this stuff really work and would it be Energy Star and/or ACCA Manual D approved? Would there be new problems created? I have never seen it done.


Asked by Anonymous
Posted Feb 17, 2010 11:34 PM ET


82 Answers

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It sort of works but it's not Energy Star or Manual D approved and is generally viewed as snake oil by reputable builders. Use real foil faced duct wrap insulation after the ducts have been sealed with duct mastic and follow up with a duct blaster test to confirm quality of workmanship, preferably have the test done by someone not in the employ of the company doing the duct sealing.

Answered by Michael Chandler
Posted Feb 17, 2010 11:45 PM ET


The claim that bubble wrap is equivalent to R-6 duct insulation is a scam and a fraud. One of the companies that sells this product — a company that has gotten into hot water for exaggerated claims — is Reflectix. When I was the editor of Energy Design Update, a reader asked whether Reflectix bubble-wrap could be substituted for R-6 duct insulation. This is what I wrote:

Reflectix insulation is a 5/16-inch-thick product consisting of bubble-wrap plastic sandwiched between layers of reflective material. According to ASTM C518 tests commissioned by Reflectix, the product has an R-value of 1.04. (Reflectix does not mention this R-value of 1.04 on its Web site; however, it can be found in a laboratory report available from the company on request.)

According to ASTM C518 tests performed by another insulation manufacturer, Glacier Bay (see www.glacierbay.com/reflxtest.asp), Reflectix has an R-value of 0.67. (The company also maintains a useful Web page -- www.glacierbay.com/Insultest.asp -- describing R-value test procedures, exaggerated advertising claims, and the Federal Trade Commission’s lack of zeal in enforcing the Federal R-value Rule.)

On its Web site, 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 (www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1362.pdf). 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.

The basis for the R-6 Reflectix claim is widely misunderstood; for example, an article called “Insulating Ducts for Efficiency” posted at Bob Vila’s Web site (www.bobvila.com/HowTo_Library/Insulating_Ducts_for_Efficiency-Insulation...), recommends the use of Reflectix as an R-5.6 duct insulation, without any mention of the need for an air space between the Reflectix and the ductwork.

Answered by Martin Holladay
Posted Feb 18, 2010 3:18 AM ET


Here's a photo of what happens when this stuff is improperly installed...and I've never seen anything but improper installations.


Answered by John Semmelhack
Posted Feb 20, 2010 9:38 PM ET


Contrary to the above comments, a foil-faced bubble insulation is a very good way to insulate ductwork, especially in hot climates. Most people don't understand how an reflective-faced material can insulate, not that the r-value testing methodology doesn't measure the reflective/low-emittance properties of these products.

First, to address the previous post. This is a photo of foil insulation in a completely different application. Most likely, it appears to be installed here is a metal roofing application. The only way I can see this much condensation forming is if the area above the foil insulation is extremely cold, and the interior is very hot & humid. In this case, the lower surface temp of the foil facing could be low enough to reach the dewpoint, so condensation forms. Personally, this photo is vague. If this is a condensation scenario, I guarantee a fiberglass insulation would be a mold utopia. Quite frankly, it almost looks like moisture is accumulated above the insulation.

Ironically, condensation is one of the reasons a bubble/foil is a BETTER choice than fiberglass duct wrap. The two bubble layers provide a thermal break separating the duct metal from the attic atmosphere. Just as the material wrapped around a cold soda can would keep moisture from forming on the outside. Without this, the can would sweat. The airspace of the bubble helps keep your hand dry.

Condensation is a real issue with fiber-based duct insulations. Unless every seam is PERFECTLY sealed (which is very difficult to do), moisture will find its way into the material. This is why fiberglass products are notorious for harboring mold, mildew and other fungi.

As for performance, the problem is that most people don't understand how foil products can reduce heat transfer, by it's ability to (1) reflect radiating heat back to the duct, or (2) by it's INABILITY to emit heat from itself to a colder airspace (Low-Emittance).

(BTW...the foil facing of fiberglass duct wrap is NOT a radiant barrier. It looks like foil, does not possess the same low-emittance properties of the bubble-foil products. The key is the emittance value of the outer facing, based on ASTM test procedures.)

It's very sad that some believe foil/bubble products are a scam, or that our products are "snake oil". It's also sad that many in our industry are responsible for this reputation...by making false or exaggerated performance claims, recommending incorrect products or installation methods for particular applications, or simply not taking the time to explain when foil insulation a good choice...AND when foil insulation is the wrong choice.

I've seen foil insulation marketed for applications where I know the product will not perform, such as where no airspace exists. These are times when foil manufacturers have to accept that traditional insulation is the better choice. Our industry hasn't done that very well.

If foil insulation has such poor thermal value, why is it used in all spacecraft? Why is it used for emergency survival blankets (for both extreme cold and hot conditions).

Why is foil inside every astronaut's space suit, and not simply a mass insulation? Because if it weren't, the radiant heat from the sun would be quickly absorbed by the fiber insulation, and the heat would be fatal. But with foil inside the suit, this radiant heat is reflected away, and/or not emitted toward the astronaut. Foil is non-negotiable in these conditions.

That alone should lend some credibility to what a foil product can do. But here's the problem...The R-Value was created to measure an insulation's ability to reduce heat transfer via CONDUCTION and CONVECTION only. RADIANT transfer (simply put, the transfer of thermal energy into the air), is overlooked. The r-value test was created to isolate an insulation's performance to 2 of the 3 modes of heat transfer. Why? Because the r-value was created to by the industry that uses it to measure THEIR products only.

If anyone wants to know the true thermal value of an insulation, they need to look beyond the r-value alone. Unfortunately, that's not how our culture has been conditioned to think. We think the r-value is some magic number that will answer every question about an insulation's performance, but it's not.

Try wrapping a hot potato in foil and leaving it out to cool. Take another and leave it unwrapped. Occasionally, check the temperature of both, and see which one cools faster. The foil-wrapped potato stays hot MUCH LONGER, even though the R-Value of the foil wrap is R-0. How can this be? It's because an insulation can have great overall thermal value, and a low r-value. It is possible, but only with low-emittance materials.

Another myth about r-values...doubling the material thickness DOUBLES the insulation value. Nope...it only doubles the R-Value. Diminishing returns. ASHRAE has documented the diminishing returns of increasing R-Values, but nobody realizes this. The traditional insulation industries don't want you to know this either. It would cut their sales, if people realized the minimal incremental gain from increasing r-values.

Someday, foil insulation will be mainstream. People will eventually understand, and you can expect the traditional insulation powers to be the ones selling these products. Right now, the status-quo suits them fine. Someday, people will learn of the "amazing" and "newly discovered" benefits of foil insulation sold by the likes of Owens-Corning, Johns Manville, etc.

For now, everyone has to wait until this is good for them, too.

There's much more to explain. I'd encourage anyone to take a closer look at foil insulation for wrapping ductwork. The more you learn, the more you'll wonder why this isn't in your house.

I'll be glad to speak to anyone directly, and try to answer any questions.

Kelly Myers
rFOIL Insulation Products

Answered by Kelly Myers, rFOIL Insulation
Posted May 25, 2010 2:00 PM ET


Kelly Myers,
Your post is a collection of half truths and outright falsehoods. It would take too long to address them all. However, I'd like to point out:

1. I stand behind my long post of Feb. 18.

2. Your statement, "The R-Value was created to measure an insulation's ability to reduce heat transfer via CONDUCTION and CONVECTION only. RADIANT transfer (simply put, the transfer of thermal energy into the air), is overlooked" is simply untrue. It is a falsehood invented and spread by marketers of radiant-foil products. To read the truth about R-value, check out "Understanding R-Value."

3. Your statement, "Another myth about r-values...doubling the material thickness DOUBLES the insulation value. Nope...it only doubles the R-Value. Diminishing returns" is also false. Doubling the thickness of a layer of insulation does indeed double its insulation value. It cuts the rate of heat transfer in half. The "diminishing returns" discussion is a reference to the cost of the insulation versus the cost of the energy saved -- an entirely different discussion from the one at hand. We're talking physics, not economics. Double the insulation and you cut the heat transfer rate in half. Period. End of story.

4. There's a good reason that foil-faced bubble wrap isn't considered "mainstream," as you put it. It is being sold by hucksters who believe in magic (and who always point to NASA, astronauts, and the space shuttle) instead of good old-fashioned physics.

Answered by Martin Holladay
Posted May 25, 2010 2:19 PM ET


I too have been incensed by the exaggerated claims buy the bubble foil folks. I'm an engineer and I have studied the physic (this is basic stuff) and know that air gaps work, and foil can reflect heat. But I drew the line when a contractor told me he could pour a slab and insulate it for radiant heat with a layer of bubble pack foil I drew the line. Reflective surfaces are not reflective if there is no air gap. So I did a bunch of tests with a heater in a box with different insulation around it. I waited until the box temperature reached equalibrum and figured that the BTU's going in are the BUT's being lost and I can calculate R factor. The tests showed an improvement of around R 2 for bubble pack over no bubble pack, same air gap. Less than what you would get if you replaced the air gap with foam. So why bother?

Sensible heat might be the reason. If you stand in a glass room in the winter at night you will feel a chill, no matter how comfortable the air temperature is. Cover the glass with foil and you will feel instantly much warmer. What's the equivalent R factor? Lots of people try, I am not convinced I believe the numbers, but I like the affect.

Answered by David Gibson
Posted Jun 2, 2010 8:00 PM ET


Cover the glass with foil and you will feel instantly much warmer. What's the equivalent R factor? Lots of people try, I am not convinced I believe the numbers, but I like the affect.

You can believe the numbers, since they are derived in the same way you determined the bubble-foil R-value. And this "foil-covered glass" is called lowE glass (glass with a thin metallic coating), the industry standard in the US. This is one of the best applications for radiant barriers, since most heat loss through a multiple-pane window is from radiant transfer between the panes. The other good application is under roofs in hot, sunny climates. Most of the rest is hype.

Answered by Riversong
Posted Jun 2, 2010 8:13 PM ET


Doesn't most insulation work on the basis of air gaps? FG has a lot of air gaps and I thought that is where the insulation gets it benefit of being an insulation. Maybe the way that Reflectix states things is sketchy but their website does say that you need an air gap for ductwork. Now Martin, you don't really come out and say it but if you leave the 3/4" air gap with the bubble wrap, will you get R-6 or not?

It seems this material is more for the DIYer than a contractor. It does take time to install but a homeowner doing the work may not care.

And by using "real foil faced duct wrap" is that really any better in terms of install? Either way seems pretty intensive.

Answered by dennis
Posted Jun 2, 2010 9:34 PM ET


Thermal insulation works by trapping tiny pockets of dead air or other low-conductivity gases within a relatively non-conductive matrix - the smaller and closer the air pockets and the less conductive the matrix, the higher the R-value.

Bubble foil traps large pockets of air within highly conductive, closely-spaced foil surfaces, so it has almost no R-value. It does have modest ability to limit radiant transfer. If it's spaced slightly away from a heat-emitting material, the low-E surfaces will reduce radiant absorption and radiant transmission.

Reflective "insulations" work best with downward-flowing heat, such as from roofs to attics or from floor to cellar. It's possible to get as much as R-8 or R-9 in a floor with one foil surface enclosing a 4" air space. As soon as you tilt the air space above 45° toward vertical, internal convection undermines the radiant benefit.

The physics of radiant barriers is relatively simple. But much of the manufacturer promotion is hype.

Answered by Riversong
Posted Jun 2, 2010 9:50 PM ET


Interesting debate. How about we get off of theory and get into the real world?

This past winter I did my ductwork with Reflectix: 2 layers and an airspace between (for the 3/4" airspace I cut 2 inch widths of it and wrapped it all the way around the duct twice. And did this every 2 feet.) Then I took my infrared camera, ran the furnace for awhile and then shot the plenum (which had no insulation) and got about 120 degrees. Then I went down the duct work a ways and shot again (all my ductwork is in the basement which is largely unconditioned). Got about 65 degrees. When I went down to the end of a duct run where I had not installed the Reflectix yet I got about 90 degrees. I had carefully taped the Reflectix joints and put extra effort into the bends. I moved the hangers so that they were always at the 4-layer points and never over an air space. My furnace does not run 100% of the time in (Maine) winter -- nobody's does. So it doesn't have to work 24x7. I'm confident that I'm ahead of the game and saving energy. Seems rather obvious, doesn't it? Your mileage may vary.

Oh, and it looks pretty impressive too -- if that counts for anything. Note: Before I started any of this I did a Retrotec Duct Blaster test and found and fixed all the leaky problems. I gained much, much more by doing that than I'd ever gain thru insulating the ducts. First things first. And I tightened up the house too, of course. Keeping that hot air in the house is the most important step of all !!

Answered by Dirk Faegre
Posted Jun 2, 2010 10:27 PM ET



What people euphemistically call the "real world" is typically no more than anecdotes. It sounds like you did a wonderful job sealing and insulating your ductwork, but if you were more aware of what you dismiss as "theory" you would know that IR thermometers are calibrated to read surfaces with an emissivity of 0.95 and cannot take accurate measurements on lowE surfaces such as bubble foil.

Answered by Riversong
Posted Jun 2, 2010 11:08 PM ET


Congratulations for having the extreme patience required to make a site-built air gap around your ductwork. I still stand behind my earlier statement: "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."

If an installer can create such an air space, and if it can be maintained without sagging, the foil-faced bubble wrap plus the air space will indeed insulate the ducts -- although there will, of course, be thermal bridging at every location where spacers were inserted to maintain the air space.

Most installers agree that it's easier to install insulation than to create such a delicate air space.

Answered by Martin Holladay
Posted Jun 3, 2010 4:52 AM ET


that photo of the dripping duct is a fraud. anyone who runs 65* temp at the t-stat will create many problems.

Answered by CJ
Posted Jun 3, 2010 9:50 PM ET


Following his WWII demobilization, Farley Mowat was sent to the Canadian arctic to study the diet of wolves. Observing that they seemed to survive primarily on small rodents, he conducted his own first-person study of the efficacy of a field mouse diet by eating nothing but (this was the true background story behind his famous novel and movie Never Cry Wolf).

When he explained his strange dietary preference to the local Inuit who kept an eye on him to make sure the "stupid one" didn't do himself in, they politely responded "Good idea".

What do I think of bubble foil duct insulation? "Good idea".

Answered by Riversong
Posted Jun 3, 2010 11:18 PM ET


I am having a home built. I want to install insulation on the outside of the home. I was planning to have 0.5 inch rigid foam insulation installed, but my framer stated he can get radiant bubble insulation. He said he normally installs this under metal roofs, but it would be as good as R value wise as 0.5 inch rigid foam. Is this true? Are there any issues with using it as an outside wall insulation method? The walls are OSB with house wrap, and we will have vinyl siding.

Answered by Chris Johnston
Posted Jun 6, 2010 11:56 AM ET


how about we try to come up with some truths instead of trying to bash one side or the other?

--space suits... truly, if the stuff is snake oil, then why does NASA use it?

--proper application... so, if it's not good for all applications, then how about telling us which it is good or bad for?

Answered by papatom
Posted Jun 7, 2010 3:54 AM ET


One half inch of foam will have an R-value of R-2 to R-2.5, depending on what foam you use -- not much. If you want to install insulation on the exterior side of your wall sheathing, you need to be sure that the insulation has a high enough R-value to avoid problems with wall condensation. The minimum R-value of this exterior insulation varies with climate, but is higher than R-2 in all but the hottest climates.

If you tell us where you live, we can tell you how thick your foam should be.

In all climates in the U.S., foil-faced bubble wrap costs more per unit of R-value than foam, and is therefore a waste of money.

Answered by Martin Holladay
Posted Jun 7, 2010 6:26 AM ET


Well first off the most important step as has already been noted is sealing the ducts properly and you will already save energy over poorly installed and unsealed ducts as are found in many older homes (I have even seen exterior stud bays with a single side of metal with the uninsulated outside wall used as a duct in some older homes that is the most extreme case of poor installations I have seen) But the fact is radiant heat gain and loss is real but it is not the primary loss. R-Value is real.
To really test this you only need look at the Low E-GLass window vs standard glass.
The R-Value of the two pains of glass with a sealed air space is the same but Radiant heat transfer is much lower with the low-e glass.
But even a minimal insulated 2x4 wall retains more heat then even the best glass window. if you want a well insulated home keep the windows on the North side small.

Answered by Anonymous
Posted Jun 7, 2010 7:23 AM ET


Re: Foil faced bubble wrap - I used it on a wall in a 17 story building with two marine boilers powering an absorbtion cooling system, which means it's on more in the summer than winter, the chimney wall was uninsulated and a thermometer taped to it read 120 degrees. I put in the foil faced bubble wrap then 1 1/2 inch studs with some fiberglass between them. The wall temp is now about 85 on the hottest days. While I don't have the math handy, I resorted to bubble wrap to avoid loosing many inches of space from the adjacent kitchen trying to beat the heat with just fiberglass, and foam in a hot enviornment, can you say "outgassing", not to mention accelerated aging. So I think radiant barriers do have uses, and if it's attached to bubble wrap, it's just a little bit extra.
Re: Wrapping duct in bubble wrap. I can think of an attic or two where I'd rather wrap that around a half dozen times than try to deal with fiberglass all over me, and, having asthma, mold is a big concern, and the one commentator is certainly right, fiberglass makes a great mold home, bubble wrap does not, and radiant heat in some attic spaces in the summer is INTENSE.

Moral of the story I think is that the answer is - IT DEPENDS - not just on pure R values, or emmisstivity, or condensation, or installation. No material or technique is a cure all in construction, you always need to be thinking, to be adaptable.

Answered by Just-An-Idea
Posted Jun 7, 2010 7:29 AM ET


Chris When I built my house I used 3/8 foil faced fan-fold insulation than put wood lath on 16 centers and hung metal siding. Tape the seams and it will qualify as a weather protective barrier.Run it into overhang to vent into attic. It sure helps keep my home cooler in summer.
Thanks Stan

Answered by Stan
Posted Jun 7, 2010 8:02 AM ET


Just a note here. No science. Layman understanding. I am a sales consultant for a frim which sells LOW-E coated windows (radiant barrier/non vapor barrier), Blown in attic insulation (fiberglass) and not bubble wrap but a foil radiant barrier and a spray on radiant barrier. I have a display of the foil radiant barrier - one side with just r-11 bat insulation and one side with same insulation and the foil radiant barrier. There is typically a 35 - 45 degree difference in the temp. below the fiberglass insulation.

My understanding. R valued insulation slows down the transfer of heat and stores it untill it can disipate it. R values I believe are determined in an environment of 75 degrees. Radiant barriers reflect the radiant heat (not conductive) back so it does not enter the space. Both are used for different purposes and should not be comaired to each other but should be used with each other. I always sell them both together.

Answered by Anonymous
Posted Jun 7, 2010 8:15 AM ET


Martin Halliday: What is a GBA advisor?

Answered by Jerry D
Posted Jun 7, 2010 8:17 AM ET


Use the product in a proper combination.

I added the bubble wrap radiant barrier to existing R-6 duct insulation and around the attic-based air handler. Additionally, I added a radiant heat barrier to the underside of my rafters running from the soffit vents to the ridge vent.

Energy savings:
July, 2007 (prior to radiant barrier) Avg Daily Use 125Kwh - Avg Temp 75
July, 2008 (after radiant barrier) Avg Daily Use 70.9Kwh - Avg Temp 75

That's a 43% savings.

In 2009 I added a programmable thermostat witht he following results:
July, 2009 (after thermostat) Avg Daily Use 58.2Kwh - Avg Temp 73
Thermostat set to 77 in the heat of the day and 73 at night for comfortable sleep

Granted there's a avg temp reduction but there another 18% savings

The payback for the radiant heat project was realized in a single year. Use the radiant products as intended and they perform extremely well especially given their relatively low cost.

Answered by Michael T. Lauer
Posted Jun 7, 2010 8:41 AM ET


"Green Building Advisor" is the name of this Web site. The term "advisors" is also applied to a group of experts who contribute to the site and help answer technical questions. (Editors are included in our list of advisors.)

More information is available here:

Answered by Martin Holladay
Posted Jun 7, 2010 9:15 AM ET



Anecdotal data is at best instructive but not necessarily meaningful. Your energy consumption figures tell us little unless you relate them to cooling degree days to normalize for variations in summer weather from year to year. Perhaps July 2008 was not as warm as July 2007. And how did July 2009 compare to the previous two?

Yes, radiant barriers work to control summertime radiant heat gain, if installed properly. Insulation works far better in controlling wintertime heat loss. Air barriers work to minimize convective losses and condensation problems. Each has its proper application and its proper methods of installation. And each are widely misunderstood, with radiant barriers (esp. bubble foil) being so overhyped that the FTC had to step in years ago to stop the worst of it.

Answered by Riversong
Posted Jun 7, 2010 9:21 AM ET


As for Energy Star approval:

The U.S. Federal Trade Commission (FTC) defines "home insulation" as "any material mainly used to slow down heat flow" (16 CFR Part 460.2). ENERGY STAR considers insulation to be products or materials that meet the FTC's definition of "home insulation" and are used to insulate a whole wall, ceiling, or floor. These products include, but are not limited to: fiberglass, cellulose, mineral wool, whole-wall spray foam, rigid foam board, cotton fiber batts, and foil radiant barrier products.

The following information must be provided for each product that the manufacturer wishes to be considered for the ENERGY STAR mark:

 R-value lab test results (or emissivity results for radiant barrier products), as required by U.S. FTC "home insulation" regulations (16 CFR Part 460).
 Consumer materials explaining what the product is, what it does, and documentation of claimed energy saving benefits.
 Clear instructions for proper installation of the product to get the benefits promoted by the manufacturer.

Answered by Riversong
Posted Jun 7, 2010 9:45 AM ET


First off, I am not in the trades. I'm an IT guy. However every spring as the air space between our dropped ceiling in our server room and the actual roof of the building would warm up, the cold duct work (the server room AC runs 24x7) would start condensing real bad and over a single weekend I would end up with large amounts of water spot damage on the ceiling tiles and sometimes even a dripping leak. Our HVAC guys came in and wrapped the ductwork with what I believe to be the topic here. It was silver stuff that looked and popped like bubble wrap. Ever since wrapping it we've had no condensation problems anymore.

I can't speak to R value or anything other than it provided what was necessary for the application we needed it for.

Answered by Gary
Posted Jun 7, 2010 10:02 AM ET


It's a scam, just like the toilet paper oil filters, the oil additives that increase gas mileage, etc., etc.
But as with all of those, the bubble wrap insulation will have angry defenders.

Answered by owen thomas
Posted Jun 7, 2010 12:49 PM ET


I have a 1964 ranch style house that was built using 2 inch fiberglass insulation in the garage ceiling. Part of my supply and return lines run through an unconditioned garage to feed the 2 bedrooms that are above the garage. When the a/c is run in the summer, the condensation is severe enough to cause dampness and mold on the garage ceiling drywall. I have ripped out the old drywall, and I'm in the process of sealing the ducts with mastic and was going to use foil/fiberglass to wrap the ducts and then insulate the ceiling with R30 fiberglass. Should this type of duct wrap product still be used in a high humidity environment or is there something better? The ceiling is still open so I can still make any changes if needed. Thanks in advance.

Answered by ArtieNJ
Posted Jun 7, 2010 12:51 PM ET


It's not a scam, but it has limited value and only when used in the appropriate applications.

As the IT man pointed out, it is an excellent vapor barrier (if seams are well-taped) and might raise the surface temperature just enough to eliminate condensation in certain situations. But it certainly doesn't meet the IECC R-8 duct insulation requirements for unconditioned spaces.

Answered by Riversong
Posted Jun 7, 2010 12:54 PM ET


I use this product to wrap our above ground sewer and water lines for our relocatable remote camps up north. We also use heat tracing taped to the pipe and then wrapped with bubble wrap. The temperature drops down to -50 celcius. I think we are using the product to reflect the heat and keep it on the pipe more so than keeping the cold from freezing the pipes. We are currently looking at alternative ways to insulate our pipes both on a temporary (one season) to permanent (1-10years) application, both still above ground.

Any suggestions? Are we using this product properly?

Answered by Keith
Posted Jun 7, 2010 1:04 PM ET


Use foam pipe insulation instead. If the pipes are exposed to the weather, protect the pipe insulation with aluminum-faced butyl tape (for weather protection, not insulation).

Answered by Martin Holladay
Posted Jun 7, 2010 1:13 PM ET


Artie Enj,
If you need to insulate your ducts, use duct insulation, not bubble wrap.

Answered by Martin Holladay
Posted Jun 7, 2010 1:14 PM ET


1964 Ranch House-retrofit: I've used a radiant barrier and duct insulation in DIFFERENT applications.

The problem is air movement from the hot, humid garage to the cold ductwork-mastic and sealing those ducts well is vital.

For air conditioning, condensation is a big issue. Making sure the duct work is sealed with mastic and, if possible, runs INSIDE the conditioned space by building an insulated chase is the best approach.

For a quick fix, you could try the radiant barrier, and make sure it is sealed/taped tight. But I think replacing the ducts with pre-manufactured, insulated ducts and enclosing them in an insulated chase is the best way to go, and even then I would prefer to use foamed-in insulation rather than fiberglass.

Answered by Jamie Wellik
Posted Jun 7, 2010 2:37 PM ET


I anyone has read down this far and still thinks bubble wrap is decent insulation, then you deserve to live in the crap you build - or have your former customers coming after you 5 years down the road after it fails, possibly causing damage to their houses. Whatever happened to common sense?

There is no free lunch and no secret to reflective insulation - it works well in a vacuum and will give you the equivalent of a little less than R-1 under the best of conditions on earth.

Yes, radiant barriers are a good deal in the desert and very hot areas, but are a waste of money in cooler areas.

So lets give it a rest and if some idiot wants to save a buck - fools rush in. I'm sticking with fiberglass and foam on my projects - and I'll pay for my own lunch

Answered by energy bill
Posted Jun 7, 2010 4:28 PM ET


When I first left home at age 17 and ventured out to the Colorado Rockies, I had nothing but a canvas pup tent and a cotton sleeping bag. So I bought one of the new "space blankets" that promised to reflect body heat back at you.

The first night I camped along a mountain road, I wrapped myself in the space blanket and slid into my sleeping bag. In the middle of the night, I awoke shivering in a puddle of my sweat. I've been skeptical about "radiant insulation" ever since.

Now that I've been designing, building and engineering for more than 30 years, I have a more thorough understanding of the physics of insulation, radiant barriers and vapor barriers. Radiant barriers have their applications (lowE windows, hot climate under-roof barriers, floor vapor/radiant barriers over a vented crawl space, and under radiant in-floor tubing), but are nearly useless in most other applications.

Answered by Riversong
Posted Jun 7, 2010 4:42 PM ET


Your post made me laugh. At age 17, I also bought a space blanket, and also shivered. I soon learned that thick down works better than thin foil -- a lesson that stuck with me.

Answered by Martin Holladay
Posted Jun 7, 2010 4:45 PM ET


To Martin Holladay, GBA Advisor - response of May 25 10
Your post is a collection of half truths and outright falsehoods. It would take too long to address them all. However, I'd recommend successfully completing a course in physics - especially since you infer you have such training.

Go look at the test process and the formula for determining R-value. It measures only conduction. It does NOT actually test convection except on a micro-scale within the insulation. Radiation is specifically precluded by the test method.

Go back to your claimed understanding of physics; doubling the thickness will double the insulation. If you double the thickness and plug that into the formula for R-value it will not double the R-value, but will yield less each time thickness is added. Go look up the word 'asymptotic' and you will know the mathmatical term for diminishing returns. End of story.

There's a good reason that foil-faced bubble wrap isn't considered "mainstream," as you put it. It is terribly expensive compared to glass.

And before you dismiss the references to the technology that allowed us to sucessfully send men into a very hostile situation unscathed, space, use some of that good old-fashioned physics (after you learn it, not before) and look long and hard at the importance of regulating radiated thermal energy.

Sometimes it seems that anyone can claim, without any merit other than that claim, to be a GBA, even Gomer's building assistant.

Answered by Berferdt
Posted Jun 7, 2010 5:34 PM ET


You have no Idea what you are talking about.
Go put on your foil hat and drink some more Tang.

Answered by John Brooks
Posted Jun 7, 2010 6:51 PM ET



In outer space, heat transfer is by radiation alone, since there is no matter to allow conduction. Additionally, high levels of protection are required against the several other spectra of deadly radiation - hence "space blankets".

Clearly, you received far too high a dose of gamma radiation when you were there, and you seem to have left a good part of your gray matter in outer space.

ASTM C 177–04, “Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus”, ASTM C 518–04, “Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus”, ASTM C 1363–97, “Standard Test Method for the Thermal Performance of Building Assemblies by Means of a Hot Box Apparatus” and ASTM C 1114–00, “Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Thin-Heater Apparatus" are all methods for determining the steady state HEAT FLUX through an insulating medium.

All those FTC-approved test methods measure total HEAT FLUX through a material, excluding any adjacent air spaces (and hence eliminating the benefit of radiant or low emissivity surfaces. Such HEAT FLUX includes conduction, internal convection, and internal radiant transfer. Thus a double-pane lowE window is measured as R-3 rather than the R-2 of a clear double-pane window because there is less radiant transfer and less convection between the two panes of glass.

With a homogeneous insulating material hot-box rated at R-N/inch, the total installed R-value is always N times the number of inches of installed thickness. In other words, for those who are not asymptotically challenged (diminishing IQ with higher math), the installed R-value of insulation is directly proportionate to the installed thickness - double the thickness, double the R-value.

Answered by Riversong
Posted Jun 7, 2010 8:06 PM ET


How good an understanding of physics do you need to realize what might be useful when exploring space and what might be useful in your basement are two very different things? Same thing with the emergency blanket thing - I don't need my home or duct insulation to be able to collapse into a convenient sized package. These things may sound impressive or reassuring but unless you consider all the different factors and how they apply to you & you're situation they're kind of meaningless.

To that end I'd be weary of anyone pushing those lines. Especially in the absence of real data & solid reason. Especially if they were trying to sell me something. Especially if that something was associated with an industry that has been known to make false/misleading claims and push snake oil type items. And especially if someone who's seems more intent on boring me than impressing me (no offence meant) is able to explain why that something is not the better option.

Answered by Brian
Posted Jun 7, 2010 8:18 PM ET


You wrote that "Doubling the thickness will double the insulation. If you double the thickness and plug that into the formula for R-value it will not double the R-value." Ah, but it will.

Doubling the thickness of an insulation material will double the R-value and will cut the heat flow through the insulation in half.

It seems you are trying to refer to another issue: the fact that each time you double the thickness of the insulation, you save fewer BTUs. That doesn't mean that the insulation isn't working; it's working very well. It just means that as the heat flow gets smaller and smaller, each doubling of the insulation is addressing a smaller and smaller problem.

Here's an analogy: let's say BP puts a device on their blowout preventer that cuts the flow of oil out of their broken well. It costs a million dollars and cuts the flow of oil in half. That's great.

If the broken oil well is leaking 16,000 barrels of oil a day, now we're down to 8,000.

Let's say they keep putting more and more such devices on the wellhead. There's a wrinkle, however: each device costs twice as much as the previous device. (After all, doubling the thickness of a layer of insulation costs more each time you do it.) The second device -- the one that costs 2 million dollars -- cuts the flow to 4,000 barrels a day. The third device costs 4 million dollars and cuts the flow to 2,000 barrels a day. The fourth device costs 8 million dollars and cuts the flow to 1,000 barrels a day. And so on.

The fourteenth time that BP installs such a device, the device costs $8.192 billion and cuts flow from about 2 barrels a day to about 1 barrel a day.

Each time they install a new device, the result is the same: the flow is cut in half. But as the flow gets smaller, the investment gets more expensive and yields a smaller reduction in flow.

Answered by Martin Holladay
Posted Jun 8, 2010 3:16 AM ET


Martin. Please advise where BP can get these devices ASAP.

Answered by James Morgan
Posted Jun 8, 2010 8:25 AM ET


Ah, Robert Riversong, you quote an interesting source in limited context, cast unqualified aspersions, and in your zealous defence of a polar position seem to miss the whole point of review and comment.
Farley Mowat was sent into the arctic on what he described as a government fund wasting fiasco where there was government money to throw blindly into an opinion-driven, pseudo-science project. We did reap one of his books from the project; the only one most people have ever heard of because Disney never made any of the others into movies. The corallary between government funding of unscientific wolf-diet research and government funded unscientific (read: opinion-driven) 'green' projects is not lost on those less inclined to accuse others of being aficed with gamma poisoning or leaving grey matter in space just because a critical view of the material presented is offered.
You cite many standards from ASTM then proceed to make the same point I was offering. Thank you for that. The standards sited do not state there is either a benefit or penalty for a radiant barrier, in fact the E-value of a window is considered along side the R-value.
You use the term heat flux, all in caps, like it has more relevence that simply using the term conduction, but it is actually a proper term for conduction per unit area. No more, except in the case one is measuring radiated heat.
Please take this for what it is worth. I did not mean to impune you. If I did, I don't think I could have done a better job of that than you have already done to yourself by decrying those who are able to do higher math.

Answered by Berferdt
Posted Jun 8, 2010 11:49 AM ET



HEAT FLUX (which I capitalized so that you might notice the term) is a vector quantity which is the magnitude of energy flow per unit area per unit time. It is a unit that is independent of mode of transfer and hence includes them all.

Your ignorance of physics is matched only by your ignorance of simple algebra (2 x R = 2R), and it is just this intelligent-sounding but thoroughly incorrect BS (and that's not building science) which encourages people to accept the hype of the radiant barrier industry and which keeps this ridiculous thread going nowhere.

Answered by Riversong
Posted Jun 8, 2010 12:38 PM ET



Answered by Ralph Townshend
Posted Jun 9, 2010 12:31 PM ET


I might not be with the current insulation ratings, but about 30 years ago when I worked in R&D for a large fiberglass insulation company there were a lot of factors that went into the rating of a bat. The thickest bat that we could make at the time was an R28. And even this bat was very irregular in its rating. It achieved an overall R28, but you had areas of the bat that were less and more in R value. The difficulty is in how you lay down the glass fibers and how the bat recovered after being flattened. In order to achieve a higher R value we took 2 bats and glued them together. I can remember that we took 2 R20 bats and this became R38. It did not acheive R40.

Now this may not hold true for foam type insulation and you may very well get double the R value with double the amount of foam. But in reality the overall effective insulation will depend upon the amount of thermal bridging involved.

Answered by Bigfoot
Posted Jun 9, 2010 3:35 PM ET



Thermal bridging is an entirely separate issue from the relationship between insulation thickness and R-value.

What you're describing is the change in compression of a fiberglass batt, which diminishes its installed R value. If you take two R-20 batts and install them together with no compression (and install them perfectly, which never happens with fiberglass), then you will get R-40.

With fiberglass batts, as much as 40% of the rated insulation value can be lost due to poor installation (which is the norm, particularly with paper-faced batts). That's why RESNET downrates fiberglass according to the quality of installation (grades I, II, and III).

Answered by Riversong
Posted Jun 9, 2010 4:08 PM ET


Slightly off topic, I used some "insulating ceramic beads" for paint. I painted equal coats with and without beads on 7/16" OSB. I could not discern any temperature difference between either the front of back of the board when measured with my infrared thermometer after and during heating by the sun. I also mentioned the board after sitting against insulation. The bead side should have been cooler. It never was. The difference between white, tan and dark green paint was quite significant. As I recall, dark green was about 40-60 degrees F hotter than white. Tan was about 10-20 degrees hotter than white. Thus insulating beads are another snake oil. I do like the gritty appearance of the paint with beads, so I may buy another type on an auction site that has a low price and no claims of insulating ability.

Answered by Derek
Posted Jun 9, 2010 4:44 PM ET


I do a lot of work in 100 year plus homes with foil backed styrofoam, Roxul mineral insulation and double thick foil bubble wrap. I use these three materials together in different combinations. The reason I have chosen this method is due to the fact that I have had to tear out traditional materials pink FB due to mould. You may say that the reason for the mould was improper installation but in many cases it is impossible to install it in a 100% correct manner as this can ONLY be done in new construction.
I have over my 20 years in the restoration business decided it is far better to guarantee a mould free system than not .
Pink insulation is a moisture sponge and this is the primary reason we need to use a vapour barrier which is immediately perforated by drywall screws and any pictures or shelves hung on the wall.
In basement situations building codes in my area of CANADA allow you to use wood and even steel studs studs on exterior walls. They have not included the concept of either heat or moisture transfer through the studs. The codes have also not considered that these brick walls are uneven and create air pockets and create condensation issues which is absorbed by the wood studs and the pink FB creating a mould environment from the backside. By using foil backed 3/4 or 1 1/12 styrofoam first and then framing the wall I am isolating the framework and the insulation contained within. For basements I prefer to fill the 1 1/2"stud (on the flat)walls with styrofoam and top it off with a layer of bubble wrap and then screw 3/4 " strapping on top of it all creating the required air space.
This system is 100% vapour barrier over 1 3/4" thick. It allows 0% air flow and will not mould.
The drywall I use is fiberglass backed and mould resistant
If your basement ever floods it will shed all moisture and will not need to be replaced.
What most people on this post have failed to notice is that ANY failure in the flimsy 6mil vapour barrier compromises your system and introduces mould which is a huge health issue.
The other issue that has been overlooked is that without the vapour barrier the r value is greatly reduced. Batt insulation only slows down the air flow but does not stop it. Bubble wrap stops ALL air flow .
To put things in a more simple way would be the difference between a balloon made of thin rubber or a balloon made of a thick wool sweater to contain hot air or even a sweater without a wind breaker on a cold windy day
Once you start to look at insulation systems and building techniques in a different light there are far more ways to create healthy warm homes. Mould is a far bigger health concern than heating costs
and foil bubble wrap offers a healthy alternative.

Answered by Anonymous
Posted Jun 9, 2010 8:24 PM ET

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