The Stovebolt Site Forums The Shop Area Interiors Insulation help?

You can also use 3M foil-faced fiberglass made for HVAC work. But it all depends on what you're trying to accomplish. Fiberglass is good for noise reduction and heat reduction when installed correctly. Foil coated bubble wrap is more for heat control only. Install any foil faced product (preferably with an air space between the foil and as much of the roof metal as possible). This is why your A/C ducts look shiny...the foil is there to reflect heat away from them. If you have an air space between the metal and the foil, it will act like a radiant barrier, bouncing heat back to the roof metal. If you do not have any air space between the foil and the metal it will help with noise if the insulation was intended to do that, but the foil will just get hot and transmit heat into the cab. The exact same thing as wrapping a potato in foil and baking it. If you want a vivid demonstration of this, get an old incandescent light bulb and hold your hand about 2 inches from it while the bulb is burning. Your hand will become very hot very fast. Now stick a layer of common foil about halfway between your hand and the bulb...shiny side facing the bulb and see what happens. And finally if you're still curious wrap your hand tightly with foil and stick it on the light bulb. You'll know how that potato feels Good luck. Personally I use the 3M foil-faced HVAC insulation and let it lay on top of the headliner.