Ultraviolet radiation reflection from building materials: characterisation, quantification and the resulting effects

Ultraviolet radiation reflection from building materials: characterisation, quantification and the resulting effects

Ultraviolet (UV) radiation significantly influences many biological entities in the terrestrial biosphere. However, the amount of UV exposure can be affected by surfaces that reflect UV radiation. Knowledge about reflected UV radiation from surfaces in the built environment is limited, especially from vertical or other non-horizontal surfaces and the resulting effects of UV radiation reflection from these surfaces. The main aims of this research is comprised of (1) characterisation of UV radiation reflection from a variety of urban building materials in vertical positions, (2) quantification of the biological effect of UV reflection from simulated structures on a human and (3) establishing relationships between UV radiation measurement indicators and resulting biological effects.

UV radiation reflection was investigated using spectral measurements made with portable spectrometers, and took into consideration factors that could influence the measurements including orientation, direction, solar zenith and azimuth angles and surface type. The biological effects due to reflection from vertical urban structures were investigated using dosimetry which enabled body site UV exposure analysis. Relationships from UV radiation reflection between different surface orientations (vertical, horizontal and inclined) were quantified. The UV Index was used to predict changes to UV exposure from certain vertical UV radiation reflective surfaces.
Spectral reflection from vertical urban structures was found to be variable and for metallic surface types the variation appears to be predominantly controlled by solar zenith and solar azimuth angles, with man-made surfaces reflecting some radiation specularly. Hence, surface type and the coating on the surface type dictates the way UV radiation is reflected from a surface. Increases in UV exposure are observed during seasons with larger solar zenith angles, and decreases in seasons with
predominantly lower solar zenith angles. This produces an observable seasonal effect, creating a potential problem in cooler seasons than in warmer seasons due to human behaviour, where personal UV protection can be overlooked compared to thermal comfort. This study has shown that UV reflection from certain vertical surfaces will substantially enhance UV exposure to an individual, and reduce the time for an outdoor worker to exceed recommended UV exposure limits.