Hi Group. I have a 30 x 40 foot metal polebarn which I use for a shop. The back third, about 30x15, has been internally partitioned and fiberglass insulated, and I heat it with forced air from a wood boiler and heat exchanger. It stays quite cozy in the winter (upstate NY), and I use it as my machine shop. Welding and storage occur in the unheated portion. I would like to add some insulation to the front portion so I can keep a little heat on in there. Has anyone got any experience with the radiant barrier types of insulation systems? I am seeing rolls of the aluminum-foam-aluminum insulation being quoted with a 14.5 R value. For example, see
stuff looks easy to install, being only 1/4 inch thick or so, but does it really work or are they being optimistic about the numbers? I could go with a conventional fiberglass system too, it will just be more work to install it.
I'd test a sample of that foil/foam stuff before I bought much of it. I'm very skeptical of their R value rating.
They may support those ratings by testing with radiant heaters that heat objects in the space while air temp stays relatively low. I strongly doubt that it has R value of 14.5 in terms of thermal resistivity.
How to test: insulate a small enclosure with the stuff. Tape the corners and seams to eliminate leaks. Put an electric heating element, as perhaps a hair dryer element or even just a power resistor, inside the box, along with a thermometer or thermocouple probe. Shield the thermometer or probe from radiant heat with a piece of metal tubing open on both ends.
Feed a measured small amount of power to the heater -- maybe 5 watts. An approximate but very simple test could be done with a 5-watt nightlight as a heater, if the thermometer is well-shielded from radiant heat from the bulb while being open to the air inside the box.
Run it for long enough to reach equilibrium temperature -- might be several hours. Equilibrium is when the temp inside the box stops rising.
The R value will be
R = dt * area * 0.293/power where dt is the temperature rise inside the box above ambient area is the total area of the box's surface and power is the power (in watts) fed to the heater. Amps * volts.
If the box was 1 foot on each side (6 square feet total) and the heater was fed 5 watts, dt would be 41 deg F if R is really 14.5.
I've not included the R value of the cardboard here so the rating will be a bit generous.
Radiant barrier doesn't have an R-Value of 14 or anything close. It's what they call a "comparative" R-Value and is a radiant barrier industry invention that has no ASTM testing behind it. A Radiant Barrier is great at what it does; reflect radiant energy. Most manufacturers claim 98% reflection and I believe it. I also believe that on a perfect 95F degree day, with a lot of sunshine and you take two identical structures and insulate one with fiberglass batts and the other with radiant barrier, you will get an identical internal temperature reading in both building if you use R-14 insulation batts in one. The logic being that "comparatively" the same results of R-14 insulation was acheived by radiant barrier and bubble wrap 1/4" thick.
Probably true on that day. Do the same on a 25F degree day and you would probably have to take all the insulation out of the other building to match the temperature in the RB building, as the RB would simply not insulate against conductive cold transfer (and probably aids it, being a metallic substance) and also reflects away the radiant energy from the sun that you WANT in the winter. Depends on your climate...
Anyway, the key to good insulation is the air seal. 2 component polyurethane foam. A contractor can spray a coat that is closed cell and practically water proof, will add structural stability to boot, and is R-7 per inch, but I'm sure has a "comparative" r-value of 30, simply because no fibrous insulation can seal out air, but who's comparing? I don't see foam manufacturers or fiberglass manufacturers using comparative R-values. The whole concept is a marketing effort. I have called RB manufacturers and the response to my observation has been that they use "comparative" or "relative" r-value because there is no R-Value test for a non porous material.
Okay. So you made one up. Commendable and creative, but building code benchmarks are created by scientists and labs such as ASTM (American Society for Testing and Materials), UL, BOCA, etc... and if they haven't developed a test that allows the marketing of bubble wrap and tin foil sandwich in a "sanctioned" way, there is probably a reason for that.
But, never offer a problem without a solution is what I live by; there's also "do-it-yourself foam kits". Just google that search phrase for lots of options. Just be sure to get E-84 fire rated and 2 component foam, not the "canned" foam like you buy at home depot. This is 600 board foot kits. Or 620. Anyway, you'll know it when you see it. Dow makes a Froth Pak, it's called and Tiger Foam is the other 'Big Name' out there.
Radiant Barriers are decent enough in the deep south or in hot climates in metal buildings that are sealed well, but if your building leaks air or if you have winter, I'd go with foam. If you have easy access to a reasonably priced contractor who will take smaller jobs, more power to you. The kits are a good option because you can get a couple and do it in stages, if you are like me and the thought of moving everything out to let them get in was a move I didn't look forward to. It's more expensive than radiant barrier, but it works. That's another reason I liked the kits. I could by one or two a month and tighten up the building as the leaks and problem areas exposed themselves and then did the all over coat just before winter hit.
I hope this helps. I mainly answered because of the R-14 claim. I think the product would sell fine on it's own merit if they just told the truth. It is good in the summer, bad in the winter. It's like painting the roof silver..
Thank you, this is a very helpful post. The lack of any ASTM or other governing body certifications is what made me uncomfortable about the radiant barrier insulation in the first place. I imagine the stuff is helpful in arizona under the hot summer sun, but probably is not going to be so useful in gloomy cold upstate NY. I'm looking into the foam options from local suppliers now. Thanks!
Some associates of mine who live in Aridzona put up the modern versions of qounset huts, and had them foamed inside. This works very very well
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
I have a few publications on insulating that include data on the use of aluminum foil for insulation. The good and bad is that it depends on the direction of the heat flow. If the heat flow is down, then aluminum fail works well. So in Arizona use aluminum foil in the ceiling to insulate the summer heat. In New York for the winter use aluminum foil in the floor. The reason is that if there is no heat flow by convection ( warm air rising ), then radiant heat flow is the major way the heat moves.
I'm thinking of nominating the former owner of this house as Canada's worst handyman. One of his efforts was to install kraft backed foil on the lower half of the basement wall between the 1 x 2 strapping and the sawdust board paneling (nothing up top). Gerry :-)} London, Canada