Hi Wendy,

Thanks for your question concerning insulating paint.

In my personal and professional opinion, I say no. I don't believe insulating paints live up to their internet hype. There are many reasons for my conclusion, so let me begin with the name "insulating paint." It's a misnomer. Paints don't and can't insulate anything, plain and simple. This is because paints don't have an R-value.

Now what paints can do in certain applications like roofing and southern/western facing walls is reflect solar heat. More so in roofs, but I can see the applications on certain exterior walls. This is the basic concept behind a "Cool Roof," which according to the Cool Roof Rating Council (http://www.coolroofs.org/) "reflects and emits the sun's heat back to the sky instead of transferring it to the building below."

Now back to the "insulating" properties of these paints. The basic equation (Fourier's Law) for conductive heat transfer (heat transfer through a material such as a wall) is as follows:

q = k*A*(Δ T) / Δ x

where
q = amount of heat transfer (Btu/hr)
A = cross sectional area of matieral (ft^2)
Δ T = change in temperature across the material (degrees F)
k = thermal conductivity of the material (Btu/hr-ft-F) -- this is the ability of the material to conduct heat
Δ x = thickness of material (ft)

The thermal conductance of a material is defined as the thermal conductivity k divided by the material thickness Δ x. The reciprocal of thermal conductance is thermal resistance, which is also known as the R-Value.

The point of this exercise is that by inspecting this equation, it's obvious that the way to reduce conductive heat transfer is increase the material's R-value. This is why you put insulation in your walls and attic with a high R-value. Since insulating paints have little to no R-value (or thermal conductivity for that matter), there is no way it can reduce conductive heat transfer.

I have seen claims by these paint manufacturers that their product can reduce convective and radiative heat transfer as well, but the main source of heat transfer in a wall material is conductive.

Other entities have also disputed the claims of these "wonder" paints as well. I have included a few links below from reputable sources for your reading pleasure.

Article from Scientific American (July 15, 2009): http://www.scientificamerican.com/article.cfm?id=benefits-of-insulating-...
Article from Treehugger.com (July 18, 2008): http://www.treehugger.com/files/2008/07/ceramic-insulating-paints.php

Also of note: The Dept. of Energy's Energy Star program does not give the Energy Star label to insulating paints for walls, but does for roof coatings.
http://energystar.custhelp.com/cgi-bin/energystar.cfg/php/enduser/std_ad...

So to summarize, if you are going to use one of these new "reflective" paints as a roof coating, you will no doubt create some energy savings. But using it on your walls probably won't give you much of a return on investment.

But not to worry -- most of the heat transfer in a building comes through the windows and roof. Concentrate on those areas and you'll get the most bang for your buck.