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 infrared (IR) pigmented coatings and the ceramic-filled paints. 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 pigment based technology in exterior coatings is a German invention and was first used in the field in the hot Australian outback over twenty-five years ago. Their effectiveness always depends upon the darkness of the coating color and how exposed the surfaces are to direct sunlight. Infrared reflective pigments actually work optimally in the darker colors when compared color-for-color to standard, organically pigmented products, the differential generally running 20 to 50 degrees F. cooler for IR pigmented coatings versus the standard exterior paints.
On roofs similarly, the greatest efficiency occurs where darker roofs are topcoated over with optimized cool colored, IR pigmented coatings. Even a color black IR 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. This is revolutionary and applies to colored coatings with IR 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. Not all whites are the same however (look for a future post here). Concentration of titanium dioxide and what it is bonded into gives most color white its main infrared reflectivity. However, even grey and beige are now available that are within 10-12% of the solar reflectance of top white reflectivity due to the efficiency of their IR pigments.
COOL COLORS BASED ON INFRARED PIGMENTS CAN DO THE WORK
SEE: Lawrence Berkeley Labs Cool Color Database
Key: The IR reflective pigments with mixed metal oxides do the work of reflecting the invisible, sun’s-heat wavelength, 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), these 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 less fast, as well as the building materials underneath them, whether walls or roofs mainly since they themselves are so much cooler in sunlight than the bare material or when covered with regular paints. Not to confuse, these coatings wear less in part also because they fully block the ultra-violet (UV) wavelengths component of sunlight, which carries no heat, but which does actively break down all 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 attract dirt. 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 manditory “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) 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 specific reflection of the infrared, thermal wavelengths from the sun, which heat up surfaces in contact with direct sunlight.
Filed under: LEED Credits, cool coatings, cool exterior coatings, cool paints, cool roofs, cool wall, heat reflective paint | Tagged: cool roofs, cool walls, green construction, green paints, Heat Island Effect, heat reflective coatings, heat reflective paints, Home Owner Associations, insulating paint, LEED, Michael Biel, solar reflective coatings, solar reflective paints, sustainability
