Building energy efficiency and fire safety aspects of reflective coatings

Abstract

Radiant energy exchange between the exterior surfaces of buildings and the environment has a significant impact on both the energy requirements for cooling and heating, and on fire safety. These issues of energy efficiency and fire safety are usually examined separately, but in this paper the interaction between these issues is discussed, with emphasis on reflective coatings. The important spectral ranges for radiant control are, in micrometers (μm), 0.3–2.5 (sunlight), 4–40 (300 K environmental thermal radiation) and 1–10 (fire). Benefits can be obtained from the development of improved coatings which reflect adverse energy flows and absorb (and emit) favorable energy flows. As a specific important example, white coatings with high solar reflectivity and high IR emissivity can significantly reduce energy use for cooling. Another benefit of high IR reflectivity in the 1–10 μm wavelength range is enhanced fire safety due to the reflection of IR radiation emitted by fire. Due to overlap of the fire spectrum with both the solar and 300 K thermal spectra, fire retardant coatings can either enhance or impair energy performance. From a research and development point of view there is considerable synergism between coatings for improved energy efficiency and fire safety. Technology developed for improved energy efficiency can be adapted (transferred) to coatings for reflecting fire radiation, and vice versa.