Paint it black

Black pigments designed to reflect the sun's heat could decrease the amount of stress on materials and save energy if used in coatings on domestic roofs.

Developed by

, the pigments differ from carbon black — the standard black pigments — because they reflect, rather than absorb, most of the invisible near infrared (NIR) radiation, which accounts for more than 50 per cent of the total incident solar energy.

The company is offering three grades — Paliogen Black, Lumogen Black and Sicopal Black — which have different NIR reflecting capabilities.

Paliogen and Lumogen both reflect up to 45 per cent of the total incident solar radiation energy, and Sicopal up to 30 per cent — and nearly all of the NIR, which is responsible for heat build-up.

By comparison carbon black has a known total solar reflectance (TSR) of less than five per cent. In trials, the lower NIR absorption compared to other black pigments resulted in a temperature decrease of up to 20ºC on the surface. So if these pigments were used in a roof coating they would not only be able to reduce material strain by releasing thermal expansion, but would also be able to keep homes cooler and save energy used by air-conditioning.