I have looked into these products a lot as well... Currently I reside in the "Skeptic" camp. For one reason, I will quote the front page of one major maker of these products:
"XXXX 's insulating paint products are based upon our exclusive blend of insulating ceramic microspheres or "vacuum beads", that are designed specifically for mixing into paints, coatings and composites to form a tight interlocking matrix which reduces conductive heat through the painted surface. The ceramic barrier reflects up to 90% of the heat back to the source."
The two ways they claim this product "insulates" is by (1) slowing down the conduction of heat, the way most insulations work, and (2) reflecting the heat, the way a mirror would.
I'm no scientist, but I enjoy reading about science and physics and have a basic understanding of heat and energy transfer, and what I do know is that the first claim of reducing conductive heat is absolutely bogus. No film only a few mils thick is going to have a significant effect on slowing heat convection, no matter how full of "vaccume beads" it is. Look at a thermos bottle - sure it works good at insulating, but it has over a quarter inch of vaccume usually, PLUS it is regularly insulated, and it still will let the heat out eventually. when you get down to a few mils (the actual "vaccume bead layer" will be even tinier), the effect would be neglegable - even if there were a perfect vaccume layer - which theres NOT.
The reflectivity of the stuff is the only argument that might hold a little water, and if you do some research, you will find that this is the type of "insulation" principle the manufacturers will claim this stuff works on (that means the promo statement I quoted is an outright LIE). I am skeptical for a few reasons:
-To my knowledge, for something to reflect heat, it has to be exposed on the surface. for instance, if you paint a mirror, it loses ALL its reflective value. These microbeads would have to lie on the surface of the paint to reflect any heat, and since they arent clear, and they dont change the color of the paint, I'd say they arent all on the surface.
-The manufacturers explanation of the effect is thoroughly fishy - Tests has shown that painting with the ceramic additive doesnt significantly affect the surface temp of a painted surface or its emissivity. They claim this doesnt matter, that the wall behind the paint will be cooler. Lets take this back to what we (think) we know about reflectivity - it takes place on the surface. A mirror's surface temp will be much lower than a surface with lower reflectivity if left out in the sun. Also, once the surface is hot, it becomes a matter of the surface and substrate's resistance to the flow of that heat (r-value or conductivity) that determines wether that heat will penetrate, and we know that the ceramic stuff doesnt effect that...
-Finally, even if all my science is wrong, these companies that sell this stuff are SHADY as hell. The one that had the aforementioned quote has at LEAST 6 different websites, with different names and search engine submissions and they all link to each other - TRICKING search engines to point to them more often - tactics used by most scam sites. ALSO, their sites are full of hype, "testimonials", and misleading quotes like the one I posted above, but NO SCIENTIFIC PROOF OR STUDIES that show these things work. They have "Gas and Cooling Bills" from customers... HAHAHAHHAHA... nice try. And the research they do quote is NOT independant NOR is it conclusive.
Take this all with a grain of salt. this stuff may be a miracle product after all, but I am just a skeptic.
good luck with your research, and let us know if you find anything substantial!