Thermal Emittance Evaluation of Coatings for Use as Interior Radiation Control Coatings
Especially formulated coatings and paints are used in building applications to conserve energy. A large number of products called “radiation control coatings (RCC)” are used on exterior surfaces to reduce the amount of solar energy absorbed by the surface and transported to the interior. A second class of products called “Interior Radiation Control Coating Systems (IRCCS)” are available for use on interior surfaces to reduce heat transfer from the adjacent interior air to the coated surface. Consensus standards for both product types have been developed by the American Society for Testing and Materials (ASTM). This evaluation was undertaken to determine the suitability of specific paints and coatings for use as IRCCS. The ASTM document for IRCCS (C 1321, “Standard Practice for Installation and Use of Interior Radiation Control Coating Systems in Building Systems”) states that an IRCCS will “normally have a far-infrared emittance of 0.25 or less”. The ASTM standard also identifies the method for measuring the emittance (C 1371, “Test Method for Determination of Emittance of Materials near Room Temperature Using Portable Emissometers”).
The standards organization, ASTM, has identified a class of coating materials, specified the controlling energy conserving property, and identified the method for measuring this property. The energy conserving property is identified as “thermal emittance” in this report. Following the lead provided by the ASTM, 16 products were tested for thermal emittance and classified as an IRCCS if the ASTM standard (thermal emittance less than 0.25) was met. The paints and coating were applied in accordance with the manufacturer’s instructions and tested in accordance with ASTM C 1371 by an independent laboratory accredited by the U.S. Department of Commerce (NVLAP) for this type of measurement.
The following table contains the thermal emittances that were measured. Each of the thermal emittances in the table is an average of three measurements.
Measured Thermal Emittances for Sixteen Coatings
| Product | Manufacturer/Distributor | Emittance | IRCCs |
|---|---|---|---|
| Radiance E025 | Chemrex | 0.23 | yes |
| Formula A Barrier Coat #85 | Hy-Tech | 0.66 | no |
| Formula A Barrier Coat #85 | Hy-Tech | 0.70 | no |
| Barrier Coat #233 | Hy-Tech | 0.89 | no |
| HeatShield R-20 | Kwik Co. | 0.90 | no |
| Koolcoat | Pawnee Specialties | 0.86 | no |
| Radiosity 3000 | Green Building Supply | 0.89 | no |
| E-Barrier | Sherwin Williams | 0.36 | no |
| Heat Bloc 75 | STS Coatings, Inc. | 0.22 | yes |
| Heat Bloc-Ultra | STS Coatings, Inc. | 0.195 | yes* |
| Lo/Mit-1 | Solec-Solar Energy Corp | 0.23 | yes |
| Lo/Mit-2 | Solec-Solar Energy Corp | 0.23 | yes |
| Lo/Mit-II Max | Solec-Solar Energy Corp | 0.147 | yes* |
| Insuladd-RBC | Tech Traders | 0.59 | no |
| Insuladd-White | Tech Traders | 0.90 | no |
| Insuladd-White on RBC | Tech Traders | 0.86 | no |
| Therma-Guard White | United Community Services of America | 0.86 | no |
| Therma-Guard Silver | United Community Services of America | 0.57 | no |
| Therma-Guard White on Silver | United Community Services of America | 0.85 | no |
* The two products shown in blue were added following the original 2006 study. These are ‘Verified Products’ by RIMA International. You can find more information on Verified Products by visiting rimainternational.org/index.php/verify
This study identified four products with thermal emittance less than 0.25 that satisfy the ASTM criteria for an interior coating intended to reduce radiant heat transfer to and from the coated surface.
David W. Yarbrough, PhD, PE
R&D Services, Inc.
June 20, 2006
Revised December 13, 2010