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Australia has a very high rate of skin cancer, so it’s not surprising that the country has led the world in the development of shade cloth, Chris Nolan told attendees of a shade cloth educational session at IFAI Expo 2019 in Orlando, Fla.
“Even in the temperate areas where most people live, we have an outdoor lifestyle,” said Nolan, managing director of Nolan.UDA Pty Ltd, New South Wales, Australia. “The issue is that we have a very high UV index seven months of the year.”
The Australian standard AS 4174:1994 was the first standard worldwide that was specific to shade cloth and its outdoor applications, Nolan said. A 2018 revision introduced a subsection “Human shade protection fabrics,” which included:
- A new rating measure termed “Ultraviolet Effectiveness.”
- Performance requirements for the resistance of the fabric degradation by light, including limits on strength loss and color fading.
Terminology for rating the degree of solar protection offered by shade cloth includes shade factor or shade coefficient, UVR block, ultraviolet effectiveness or UVE, cover factor, PAR, and ultraviolet protection factor or UPF.
Shade factor or shade coefficient is the percentage of normally incident radiation between 290nm and 700nm (that is, both UV and visible light) not transmitted through the material.
UVR block is similarly defined, but with a narrower wavelength band between 290nm and 400nm (both UVA and UVB).
Ultraviolet effectiveness or UVE is similar to UVR block, but the calculation puts more weighting on the biologically damaging UVB radiation (that is, wavelengths between 290nm and 320nm).
Although determined by the degree of radiation penetration of the specific wavelength 350nm, cover factor is designed to be a relative measure of the percentage area of the cloth comprising yarn and fiber, or density, rather than shading effectiveness.
PAR is the percentage of photosynthetically active radiation (radiation that promotes plant growth) that passes through a fabric.
Ultraviolet protection factor, or UPF, is a measure similar to solar protection factor (SPF) of suncreens. Basically, it’s the duration of exposure required to accumulate a sun-burning does of radiation relative to no protection.
In addition to a shade cloth’s protective ratings, the design of the structure itself must be considered when determining the effectiveness of a structure to protect people from harmful doses of sun, Nolan said. Designers should consider the location and angles of the sun during the summer months and the times of day that the structure will likely be in use. For example a school playground is more likely to be in use during morning and mid-day hours, so the location of the sun’s rays and the shadows cast by the structure in those hours would be key to a protective structure.