A few years back Bob Vila did a show on building a shipping container house with all sorts of claims, here’s a link. Part of what he covered was this miracle product, a ceramic paint, and I’ll quote directly, “TAW uses xxxx insulative coating, which is sprayed on both sides of the remaining container walls to prepare the house for heating and cooling loads. Supertherm is a high-performance, four-part ceramic coating that carries an R value of R-19 and adheres to the steel surface of the shipping containers. “It really worked,” says Shannon Locklair, project superintendent for the North Charleston house. “We had an open house one day when it was 85 or 90 degrees out and the air was at least 10 to 20 degrees cooler inside. This was before we had even installed the windows.”
Naturally every time something appears on the web about shipping containers, I get deluged with calls. This time was no different, and the idea of insulating paint interested me. I was rather confused, since I have done design work with Appendix J of the ASHRAE standards, and I have had thermodynamics in college. How could a material as thin as paint stop heat transfer? A ceramic pain manufacturer sent me a book of test reports along with a letter from the testing agency claiming the product had an “R19 Equivalent”. No explanation, just that statement. No information about the guy that signed the letter. Was he an engineer? What was his qualifications? I have no idea.
So, I read through all the test reports, and I didn’t see ANYTHING that indicated that this material had any sort of R value. Understand that R value is the inverse of the “U” value. U is a measure of conductance of thermal energy in a material. Let’s say you make a chamber and divide it in two with an insulating material. You heat up one side. If you measure how long it takes the heat to cross over the insulating material and heat up the other side, you can calculate the thermal conductance. That is a fraction, so you invert that number and you get a whole number and some decimals. Round it to the nearest integer and that is basically how you get R value. Think about it – how can a thin material stop the temperature from crossing the barrier?
For the scientifically inclined among you, lets get to the molecular level. Heat is energy and it causes molecules to move about faster. By moving faster, the molecules force a solid like ice to become liquid, and as they move faster they cause the liquid to become a gas, in the case of water, it becomes steam. In that warmer side of the chamber the molecules are moving faster than the molecules on the colder side of the chamber. The moving molecules bump up into the molecules of the thermal barrier and cause them to move faster. They in turn bump into the molecules on the other side of the chamber causing them to move faster, and that side of the chamber to heat up. With a thin layer of dense material like steel, this transfer of faster moving molecules happens really fast, which is why a steel sheet is a bad insulator. The best barrier is a vacuum between two sheets of any material, like you have in thermos bottle. There are very few molecules to bounce into each other. Since vacuums like a thermos bottle aren’t feasible for a building, a thicker less dense material, like fiberglass is used to slow the heat transfer down.
How does this translate to ceramic paint stopping heat transfer? It doesn’t. It doesn’t work. Just today I found this article. Basically what happened was a guy used a ceramic paint to insulate his house and then sued the HVAC contractor. Fortunately the mechanical contractor “won” the lawsuit (it probably cost him $50,000 to $100,000 in attorney’s fees). As I started reading the article, I realized it would be pretty easy to test the house to see if the product worked – an infrared camera would tell you whether it worked or not.
It turns out the owner of the house hired a mechanical engineer to find out what was wrong, here’s what happened when he testified in court (he used the infrared camera like I would have):
“At that point King contacted Curt Freedman, a mechanical engineer, and asked him to figure out why his house was so hard to heat and cool. Freedman later wrote, “During one of my site visits, with outside temperatures of 28ºF, temperatures in the home were noted only to be in the 48ºF to 60ºF range.”
Freedman told me, “I inspected his walls with an infrared gun. I was getting very irregular readings of the inside temperature of the wall surface, so I told him, ‘There is something terribly wrong here. Is your house insulated?’ It’s a big house. I went up to the attic, and I was astonished to look at all the joists with nothing in between them. There is nothing there. So I’m thinking, ‘What’s going on?’ The owner is boasting to me, talking about xxxx. He said, ‘This is the warmest attic in Longmeadow.’ I told him, ‘There’s a reason for that — all the heat from your house is coming up here to your attic, because there is no insulation on your attic floor.’”
“After examining the entire system, Freedman evaluated the thermal insulation throughout the home,” wrote Justice Fields. “Based on his assessment, Freedman determined that the R-value of the xxx was essentially zero.” Freedman determined that the actual design heating load of the uninsulated house was 365,133 Btu/h, so it wasn’t any surprise that the 183,000 Btu/h boiler couldn’t keep up.
Some time afterwards I was contacted by other insulating paint suppliers, and of course they didn’t make the same outrageous claims, but they did claim their product reflected radiant heat. Do they? Possibly. Is it any better than white paint? I don’t know. Is the ceramic based paint better for corrosion, wear, and so on? I don’t know. Typically epoxy paint is used by container manufacturers.
I checked out company in question’s website, and they still make some pretty impressive claims. I also found this article on the American Ceramics association website: http://ceramics.org/ceramic-tech-today/insulating-ceramic-paint-distributor-falls-for-his-own-grifter-tale
Anyway, it if sounds too good to be true, it is too good to be true.