Turning a profit these days get harder and harder. Many small companies and the people they employ have to consistently fine tune and tweak to improve bottom line. Its hardly any surprise that when a product hits the market that has all the virtues of a NASA spin off, low cost, offering very impressive specifications that tradesmen will flock to it. The old saying, if it looks like a duck, walks like a duck … Aside from the virtues of this product, it installs considerably easier and is very cost effective. The foil face bubble wrap manufacturers may have a fantastic product but unfortunately market their product to an industry that is unaware of codes that restrict its use.
Heat moves by 3 methods, convection (mass air transport), conduction, and radiation. Insulation (or R value) resists heat by conduction. Most if not all insulation is designed to fight heat loss and gain by conduction only.
Heat loss and gain by radiation (again, line of sight) more importantly, resisting it, is a much trickier concept. keeping it simple, metallic or shiny surfaces have a low emissivity or poor ability to emit radiation (Heat). Think about it, when a manufacturer adds a heat sink, or metal plate to help remove heat they paint it flat black. A flat black finish can emit heat well, it has a high emissivity. Ok, so shiny silver resist heat and flat black can emit it, got it ? Good!
Insulation companies who make metallic bubble wrap (or their distributors) like to boast about their products attributes, and add the reflective values to the conductive values, giving an equivalent R-value. Some say R4, R6 or R8. Some of the better manufactures state in fine print the conductive R value. Most metallic bubble wraps are about an R-1.
Worth mentioning, to get the equivalent R value the installer has to use spacers under the insulation to keep the prescribed air gap, I have heard some say that the insulation could be installed loosely to maintain the gap. Under certain circumstances this may be a cost effective solution. Current codes don’t require insulation when the duct’s are in conditioned space. I worry about the ducts sweating during certain conditions and think the bubble wrap may be a fine choice. In addition, during the heating season the duct losses (all insulation allows heat to move) could be used to heat the area.
Now the nitty gritty, Ducts in an unconditioned space, ie. an attic is a different animal. The 2010 mechanical code of NYS says,
Ultimately, Bubble wrap should NOT be used where the code prescribes a required R value. ( Exception… if you need R-8 you can always add 8 layers)