Cool black roof impacts into the cooling and heating load demand of a residential building in various climates

• Various cool black paints using CuO and Cr2O3–Fe2O3 pigments were made in laboratory scale.
• The spectral reflectance and thermal emittance of pigmented coating samples were measured.
• The impacts of applying the cool black paints into the peak and annual cooling and heating load demand were evaluated.
• Suitability of the cool black paints for different climates was investigated.

This paper describes the impacts of different cool black paints on cooling and heating load demand of a residential building in different climates. Cool paints with dark appearance and high reflectance in near infrared portion of sunlight are of great interest by the owners of homes to satisfy both desired visual and energy saving aspects. Three copper oxide (CuO) powders, different in pigment size, and a chromium–iron oxide (Cr2O3–Fe2O3) powder, as a commercial cool black pigment, are used to make the black paints. The samples are made on both conventional black and cool white base coats. The spectral reflectance of all samples in solar range (0.3–2.5 µm) and infrared region (2.5–25 µm) is measured. The thermal emittance of the samples is estimated using the spectral reflectance measurement and validated by the measurement of infrared camera. A typical residential single-stage single-family home in three different climates of Iran is considered and the impacts of applying the different black paints on cooling and heating load demand are discussed. The results show that the peak and annual cooling load demand decrease by 0.4–1.4 kW (6–13%) and 405–2202 kWh (6–14%), respectively, depends on the type of pigmented coating and climate conditions.