Ceramic Coating-- Insulation or Reflective Surface?

Editors update 09-17-02: The federal trade commision has ruled against companies that make claims that their paints have insulative value. The formal complaint, agreement and other documents can be viewed at http://www.ftc.gov/opa/2002/04/kryton.htm.

Ecoshell coated with Ceramic Paint

In the late 1970's, there was a new paint product introduced as a ceramic coating. Essentially, the ceramic coating is an acrylic paint filled with ceramic microspheres which claim to prevent heat from crossing through them. Special ceramic tiles are used to protect the space shuttle from burning up upon re-entry of the Earth's atmosphere. Supposedly, ceramic coatings work the same way.

Monolithic applied a ceramic coating on many structures in the mid 1970's - mainly potato storages in the valleys of Idaho. Many of those potato structures were made of galvanized metal. Sunshine was heating the surfaces to extremely high temperatures which increased the speed of metal decay. When we applied the coatings, solar temperatures on the surface of the buildings dropped dramatically, thus slowing metal deterioration. We never even considered ceramic coatings an insulation. We only used it as a way to decrease exterior surface temperatures.

Ecoshell coated with white exterior paint

As we got more involved in the development of the Monolithic Dome we forgot entirely about ceramic coatings - until about 6 years ago when we developed the Ecoshell. At that time, we tried the coatings again with mixed results. I hired a man from Florida to do a test using a ceramic coating and a plain white paint. We did not use any special labs, so consequently our results are not official in any way. We could not prove that ceramic coatings insulated nor reduced exterior temperatures any better than plain white paint.

This past summer (2001) we tried another experiment. A ceramic coating applicator offered to coat a small Ecoshell to prove what a terrific insulation ceramic coating is. Our test consisted of two Ecoshells, both 10' in diameter, sitting side by side. Each was washed and cleaned. Then, one was painted with a good grade of white exterior coating. The other, we turned over to the applicator for a two-coat system of ceramic coating.

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We monitored the interior and exterior temperatures of these uninsulated EcoShell buildings as well as another empty Monolithic Dome with a sandstone-colored Airform on its exterior. We covered its south-facing window with aluminum foil in order to more closely duplicate the two storages.

[For those of you not familiar with the notations, an Ecoshell is a 2-3-inch thick concrete shell with no insulation. A Monolithic Dome, on the other hand, has 3 inches urethane insulation sandwiched between the Airform and the concrete.]

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Findings after several months of consistently monitoring exterior and interior temperatures:

The structure with the ceramic coating is showing that it reflects sunshine slightly better than the white paint. The operative word here is "slightly". We're talking, at most, a few degrees.
On the other hand, the Monolithic Dome is largely unaffected by temperature changes outside.
Solar temperature gain on the surface of the sandstone Airform is higher than white. In the direct sun, the surface of the ceramic-coated building will reach 105 degrees, The surface of the white paint coating will reach 106 degrees, the sandstone Airform surface of the Monolithic Dome will reach 114 degrees.
The interior temperature, however, through a 24-hour cycle will change less than 6 degrees in the Monolithic Dome.
The interior temperature of the two Ecoshells are staying within a few degrees of the exterior temperature as it cycles. In other words, the structures are experiencing an approximate 20-degree temperature change which is exactly what the atmosphere is doing.

Bruco, our caterpillar-shaped Monolithic Airform Manufacturing facility, has been covered with various colors of metal cladding. It is interesting to note the significant temperature differences on its surface during a very hot, August day in direct sunlight.

Outside air temperature - 105 degrees F:

Exterior Metal Temperatures:

The white metal - 108 degrees
The off-white - 114 degrees
The sandstone was hotter, followed by the copper and then the green at 142 degrees.
Black - slightly hotter than the green.

We measured no difference on the inside since Bruco is insulated with 3 inches of polyurethane foam.

I am convinced the lighter-colored fabric (white being the best) generates more savings in cooling costs even with the urethane foam. There is little doubt that the surface will degrade more slowly if it is kept cooler.

Surface color makes a huge difference on the inside of a building. This is especially true if there is little or no building insulation. It even makes a small difference on the best insulated buildings -- Monolithic Domes.

As can be seen from the graphs, there is little difference in temperature between the white paint and the ceramic coatings. Under no conditions can the ceramic coating be called an insulation. It is simply a reflective surface.

Related Articles:

Ecoshells vs. The Monolithic Dome
"R" Fairy Tale -- The Myth of Insulation's R-Value
Reaching for the E-Stars-- Dome Living Energy Savings
Lessons Learned by Monolithic in Exterior Coatings

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