The Problem

furnished sunroom with large windows and glass doors

Protecting valuable furnishings or artwork from the destructive fading effects of the sun has long been a challenge for home owners.  But what causes sun fading?

The sun radiates solar energy by electromagnetic waves over a range of wavelengths known as the Solar Spectrum.  The Solar Spectrum is divided into 3 bands. What distinguishes these bands from one another is the wavelength ranges that characterise them, commonly measured in nanometers (nm).  A nanometer is equal to one billionth of a metre.

uv light

The three bands of the Solar Spectrum are:

  1. Ultra Violet radiation (UV): 290 – 380 nm
  2. Visible light: 380 – 780 nm
  3. Infra-red radiation: 780 – 2500 nm

It is UV that is primarily responsible for sun fading. Other causes such as visible light (sunlight) and infra-red radiation (heat) accelerate the fading process, but in New Zealand, are expected to be of secondary importance.

UV levels are influenced by latitude, the amount of ozone in the atmosphere, the amount of cloud cover, reflection from surfaces such as concrete, the time of year and time of day.

In New Zealand from September to April UV levels are very high. During the daylight saving months, New Zealand has 40% higher peak UV levels than places at similar latitudes in the northern hemisphere.

UV can’t be seen or felt and outside temperature is not a good indicator of UV level.  Even when the temperature is cool, the UV level can still be very high. Furthermore, in Winter, when the trajectory of the sun is lower, UV radiation can still be a problem when sunlight protrudes further into rooms than during other times of the year.

Check out our solution to UV fading