Many considering the application of a reflective roof coating are concerned about
color. The Florida Solar Energy Center has evaluated the solar reflectance of
some 37 different roofing materials, with the measured data showing that white
roof materials generally exhibit the best performance. They are highly
reflective across the solar spectral bandwidth, while being highly emissive in
the far-infrared region--this is another way of saying they strongly reflect
solar heat and any heat they absorb will readily re-emit to the cooler sky
temperatures.
It may seem a bit counter-intuitive, but silver reflective
aluminum paints do not perform nearly as well as a simple white coating. This
is because, although the aluminum flake paints have a high solar reflectance,
they also have a low infrared emissivity--they tend to hold whatever heat they
absorb--negating part of the reflectance properties.
Fortunately, for those who demand non-white roof colors, it appears possible to
tailor paints and pigments so they are not so reflective in the visible solar
range, but are very reflective in the "invisible" near infrared region. The
U. S. Navy has conducted research in this area to help develop infrared reflective
coatings. Paints have been created that are twice as reflective in the near
infrared as in the visible region.
At Hy-Tech we to are examining spectrally selective paints that offer the possibility
of significantly increasing the solar reflectance of even darkly pigmented
colors.
Tests performed to date utilizing test procedure ASTM D 4803-93 show that pure carbon black has a heat gain of 145.4... Hy-Tech Hydro Black coating has a heat gain of only 121.8. This is slightly better than a 16 1/2% REDUCTION in HEAT for a Black coating!!
Deep Hunter Green with a heat gain of only 121.1 and Tile Red are now being tested in Australia for real time energy reduction values on various roofing materials.
A full range of colors in these highly reflective, waterbase, environmentally coatings will be available to the general public soon. Please contact our technical department for details.
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