The Reflective Insulation Manufacturers Association(RIMA) has informed members, builders and radiant contractors to beware of products labeled “radiant barrier paint.”
“The problem is, according to definitions set forth by ASTM, there is no such product currently available,” says Mary Edmondson, executive director of RIMA, in a statement. While there are low-emittance paints, which are also known as interior radiation control coatings (IRCC), there is a difference between these types of paints and “radiant barrier” paint.
By definition, according to the organization, a radiant barrier is a low-emittance surface facing a large air space. The thermal performance or the reduction of radiant heat transfer is proportional to the surface emittance of the radiant barrier material. Emittances of materials range between zero (no radiant heat transfer) and one (that of a black surface with maximum radiant heat transfer rate).
In 2006, RIMA conducted testing of several low-emittance paints to measure the surface emittance of several paint products claiming reflective benefits. Ultimately most didn’t even meet the qualifications for an IRCC, let alone a radiant barrier. (View those test results on www.rima.net under “Technical Info.”)
Both radiant barriers and IRCCs can contribute to the overall thermal performance of a building, offers Edmondson, but she urges contractors to “do their homework” before purchasing a low-emittance paint product.
“If it’s being called a ‘radiant barrier paint,’ beware! Check the emittance, ask for test data, and make sure it meets ASTM standards before you buy.”