Heat reflecting paints are usually used on buildings as external paints to reduce.the heat load from solar irradiation. They can also be used on external pipework where the pipe contents such as water, oil or similar should be protected from excessive temperatures. This paper reviews the current advertising material and published on the internet by heat reflecting paint suppliers including those who use hollow silica/ceramic spheres. The aim of the paper is to give a better understanding of how they function and of the benefits of this type of paint. The way that they function is not by being, as claimed, an insulation layer similar to heat shuttle ceramic tiles or thermal insulation batts. It is actually by the inclusion of low refractive index ‘bubbles’ within the spheres acting as shorter wavelength infra-red scattering centres within the paint body. The data in advertising material that is supplied in the form of reflectance spectra and temperature measurements supports the claims of lowered external surface temperatures. Based on the available data, this paper shows that these paints have virtually no insulative effect as such. The benefits result from lower heat radiation into the roof space or pipework and lower conduction/convection from the roof or pipe surface irradiated by sunlight. Generally, the most cost-effective way to minimise surface heating from solar radiation is to use standard pure white acrylic paints. In critical situations, the expense of a heat reflective white paint may be justified. In cases where glare from pure white paints is likely to be problematic then as light as possible a colour of heat reflective paint should be used. The increased heat gain through using paints darker than pure white can be partly mitigated by using heat reflecting paint additives with hollow ceramic/silica microspheres and/or using pigments that scatter infra-red radiation effectively.
Heat reflective paints have been available for the last fifteen years. They are beginning to be used in industrial and architectural applications to give significant cost savings through reduced energy use for temperature control. These paints are used to reflect the heat component of sunlight, which leads to a reduction of exterior surface temperatures and thus the heat load on buildings and pipework. Many of these paints employ silica/ceramic microspheres to reflect infra-red radiation. The area has hardly been covered in the scientific or engineering literature. This paper explains how they function and is a review of some of the advertising material and claims in the heat reflective paint field.