Self-thermostatting organically coated steel cladding using thermochromic materials

Abstract

This paper explores the effect of colour and gloss on the solar/thermal gain achieved by organically coated steels (OCSs) under external and artificial exposure conditions. External and artificial exposure tests have shown that the colour of an organic coating has a dramatic effect on the thermal gain. Otherwise identical black and white panel assemblies have been found to experience average thermal gains of 16 K and 1·6 K, respectively, over a typical UK daylight exposure. The coating gloss also affects the solar gain but to a much less significant level, with the thermal gain for standard panel colours changing by only 2·5 K when gloss levels are altered between 80 and 10%. Thus, the colour of the organic coating was the most important factor controlling thermal gain. To control solar gain, novel panel assemblies have been prepared in which thermochromic inks with two temperature dependent colours have been incorporated with an OCS topcoat. These have been compared with traditional OCS products, with similar colour and gloss to the two extremes of colour of the novel material. It has been found that as the temperature of the test panels rises and the colour of the organic coating is converted to its lighter shade, the thermal gain of the panel assemblies is lowered and thus the panels have a self-thermostatting capability.