Solar reflective coatings vs. Insulating paints – What’s the truth?

SOLAR REFLECTIVE DOES NOT MEAN IT INSULATES

In the market today you will find two competing exterior finish coating and finish paint technologies which claim the top results for their ability to reflect the sun’s heat.  These are the solar reflective coatings or IR reflective coatings (IR=infrared) and the so-called insulating paints that are ceramic-filled. By definition, the nature of coatings provides for part of the difference compared to paints, since coatings are thicker and more adhesive. Coatings source from an industrial heritage where performance demands were placed by companies requiring longer life cycles across all types of uses.

The infrared (IR) pigments technology in exterior coatings is a German invention and was first used in the field in the hot Australian outback over thirty years ago. Their overall effectiveness depends upon the darkness of the coating color and how exposed the surfaces are to direct sunlight. The infrared reflective, inorganic pigments actually work optimally in the darker colors when compared on a color-for-color basis to standard, organically pigmented paints, the differential generally running 20 to 50 degrees F. cooler for specialized, mixed-metal oxide pigmented coatings.

On roofs similarly, the greatest efficiency occurs where darker roofs are topcoated over with optimized cool color coatings (solar reflective – IR reflective). Even a color black coating, in examples I have witnessed, can be well over 40 degrees F. cooler when applied to a black composition shingle roof or cap-sheet in the correct IR pigment formula. This is revolutionary and applies to solar reflective coatings with IR reflective pigments only in a range of efficient colors. Of course, the color white is the most reflective of all colors. Many companies with no specific infrared pigments, claim the greatest solar reflectance for their white only topcoat. However, not all whites are the same (look for a future post here). Percentage concentration of titanium dioxide, its particle size and purity, and what it kind of quality base it is blended into gives color white its main infrared reflectivity.   However, even grey and beige are now available that are within just 10-12% of the Solar Reflectance efficiency of color white!  This is due to the reflective efficiency of the IR pigment technology. (Learn about ECO-THERM Elastomeric coatings)

COOL COLORS BASED ON INFRARED PIGMENTS CAN DO THE WORK

SEE: Lawrence Berkeley Labs Cool Color Database

Key: The IR reflective pigments with low toxic, mixed metal oxides do the work of reflecting the invisible, sun’s heat wavelengths, the infrared. The tough, water-based acrylic, thermoplastic coatings and acrylic elastomerics coatings made to carry these pigments bond exceptionally. In reflecting away the majority of the solar radiation (the common phrase description for the  infrared heat wavelengths), cooling coatings hold up longer because they are engineered both more cohesively and with greater ability to handle a wider range of thermal shock than paints.  The coatings themselves wear much slower, as well as the wear on building materials underneath them, whether walls or roofs, since they themselves are so much cooler in sunlight than the bare material or when covered by regular paints. Not to confuse, these coatings wear less in part also because they fully block the ultra-violet (UV) wavelength component of sunlight, which carries no heat, but which does actively break down all sun-exposed coatings, paints, films and plastics over time.

COOL ROOF COATINGS  with  REFLECTIVE COLORS  – SECRETARY CHU SPEAKS

Color for color these cool reflective coating products  will be cooler than standard pigmented coatings or paints, even in the color black. In the color white, optimal reflectance will be dependent upon other factors than just the white, titanium dioxide they contain, such as surface smoothness, use of high concentration of top acrylic and no plasticizers to adhere dirt particles onto the coating. U.S Energy Secretary Steven Chu speaking in London on May 26, 2009 made the first press release from the Obama Administration touting the cool roofs information and as well,  the capability of cool reflective colors with “special” pigments.  He is talking about the same subject as we are here.

SEE: Energy Secretary Chu’s Comments

CERAMIC PAINTS CLAIM TO INSULATE AND TO REFLECT HEAT

Ceramic-filled or so-called ceramic insulating paint additive technologies promoted by several companies claim to be an”insulating” paint panacea to make exterior house walls cool have been a nonsensical concept from their outset based upon just one law of physics. Since insulation and it associated mandatory “R- value” measurement in the building industry (R for resistance) have been long established as the  measure of effectiveness for insulation. This is based on thermal mass (thickness & density) and in some varieties, effectiveness in trapping air inside the thick barrier or dense product.  Average paint thickness is a single sheet of paper. Now comes the two sheets of paper thick ceramic-filled paint (up to TEN pieces pieces of paper for some manufacturers), and the claims of insulation value when used to paint any type of exterior wall.  Buildings coated in this way are claimed to be so cool so as to be compared to the space shuttle in how it is protected by ceramic tiles in re-entry to our atmosphere.  This is all smoke and mirrors since the very basis for the R-values claimed cannot possibly be achieved for any substantial length of time by thousandths of an inch of any paint film with insulation elements (ceramic or hollow glass) mixed inside of it.

The paints that are said to insulate do not use the IR pigments at all and would be seen to rely upon the insulative idea for the gains they promise as opposed to true reflection of the infrared, thermal wavelengths from the sun, which heat up surfaces in contact with direct sunlight. SEE:  FTC Cases AGAINST Insulative Paint Manufacturers and,  http://www.ftc.gov/opa/2002/04/kryton.shtm