Does radiant barrier paint work as well as reflective insulation?

Simply put, no. In order for a product (paint, foil or metallic film) to be classified as a radiant barrier, defined by ASTM, the product must produce at least 90% reflectivity. The Reflective Insulation Manufacturers Association (RIMA) says the reflectivity of "radiant barrier paints" range from 10% to 75%, which will provide drastically different results compared to the best radiant barrier insulation. In fact, the application of a ceramic radiant barrier paint to the underside of roof is not an easy do-it-yourself project as the fumes are noxious (VOC respirator needed). If a paint does not conform to ASTM C 1321, "Standard Practice for Installation and Use of Interior Radiation Control Coating Systems in Building Systems", it should not be considered for interior applications in the attic.

In addition, before you consider purchasing reflective paint or a reflective metal barrier, make sure it is Energy Star certified and has a Class A fire rating. Typically any Energy Star qualifying product will have a corresponding label/logo on the packaging.

Energy Star certified Enerflex Radiant Barrier is a metalized film that has a class A/1 rating for fire and smoke. It also meets the new mounting requirements for ASTM – E84 under E2599. ASTM E2599 is the new industry standard which will be reflected in the 2012 building codes. ASTM standards are adopted by organization such as IECC, IBC, IRC, and ICC.