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Abstract: Contaminants from cool-pigmented roof samples exposed at seven California sites were analyzed for elements and carbons to identify those that degrade or enhance solar reflectance. The losses in solar reflectance varied by site and the color of the sample. The least reflectance drop was observed in the alpine climate, while the largest drop occurred in sites near urban development. The change of reflectance appears cyclical with the onset of seasons having more rainfall. A deposition model suggests that chromium ranks first, iron second, and elemental carbon third in importance to soil light absorption. [Copyright &y& Elsevier]

• Two photocatalytic architectural membranes were exposed alongside a control sample. • Specimens exposed at three California sites with different weather & pollution levels. • Photocatalytic samples showed excellent self-cleaning performance after two years. • De-NO x efficacy depended on weather, pollution, and type of photocatalytic material. • De-NO x efficacy showed seasonal effects associated with raining/dry periods. Photocatalytic self-cleaning "cool" roofs and walls can maintain high albedos, saving building cooling energy, reducing peak power demand, and mitigating the urban heat island effect. Other environmental benefits result from their de-polluting properties. Specimens from two different photocatalytic architectural membranes and a non-photocatalytic control were exposed alongside vertically, facing west, for two years at three California sites, and retrieved quarterly for testing. Photocatalytic materials showed excellent self-cleaning performance, retaining albedos of 0.74 – 0.75. By contrast, the control material exhibited an albedo loss of up to 0.10, with appreciable soiling observed by scanning electron microscopy. De-pollution capacity was assessed by quantifying NO removal and NO x deposition rates at 60 °C. Efficacy varied with exposure location, weather conditions, and the nature of the photocatalytic material. Seasonal effects were observed, with partial inhibition during the dry season and reactivation during the rainy season. [ABSTRACT FROM AUTHOR]