Cold coatings – what are they?
Sunlight gives us warmth and life. As humans, we appreciate the sun’s energy, but we are also wary of its unwanted side effects, especially on the skin. The same applies to buildings that are heated by the sun either directly or indirectly. Sunlight emits UV radiation as well as invisible infrared radiation (IR), which are harmful to all types of substrates and heat objects to potentially uncomfortable and often unacceptable levels.
Dark surfaces absorb solar energy and convert it into heat, while light surfaces reflect most of the solar energy. Most dark surfaces become very hot when exposed to sunlight and require more cooling. A telling fact is that in urban areas with large populations, the air temperature is 3-10 °C higher than in rural areas.
A high surface temperature can have a negative effect on the coating, especially if it is black or another very dark shade. Light surfaces reflect incident light, while dark surfaces absorb it and convert it into heat. The temperature of a dark surface exposed to the sun can reach an incredible 80 °C, while on a light background it stops at 40‒50 °C.
Cold coatings increase the reflection of sunlight. Unlike conventional coatings, which only reflect sunlight’s visible part, cold coatings also reflect the IR part of the solar spectrum, and as a result the surface heats up less.
Due to the lower temperature, cold coatings are more durable and can easily be used for tinting in dark shades.
Cold coatings are made using IR reflective or cold pigments. These reflect a large portion of the invisible near-infrared waves (NIR) and thus reduce surface heating. At the same time, all visible light is absorbed which maintains the black visual appearance.
TSR (Total Solar Reflectance) expresses the ability to reflect sunlight in percentages between 0 and 100. A value of 0 means that the surface absorbs all solar radiation; a value of 100 means that the surface reflects all solar energy.
A high TSR factor therefore means that the surface does not heat up and maintains a low temperature. White coatings, which usually contain titanium dioxide (TiO2), are the coldest, as with an average value of TSR=80, TiO2 reflects most of the solar energy.
Designers and architects want a greater choice of colours with the properties of light shades that reflect most of the solar energy and consequently stay cool. Unfortunately, classic coatings do not have these properties, in which case the only sustainable solution is to use coatings with IR reflective pigments.
Cold - IR reflective coatings can be used to reduce heat generation in objects exposed to sunlight, resulting in local energy efficiency and improved physical properties, including the visual appeal.
In our new Exterior Colour Collection colour card, all the shades are prepared from the most weather- and UV-stable inorganic pigments. Although we recommend choosing lighter shades with less heating for façade surfaces, dark façade tones can now also be a good choice thanks to IR reflective pigments. 70 selected dark shades (marked ☼IR on the colour card) can be prepared with IR reflective pigments, which allows a lower surface temperature compared to the use of classic pigments. This significantly extends the service life of dark façades.
The energy efficiency from using IR reflective coatings brings added value to existing buildings.
The use of IR reflective coatings has been proven to reduce thermoplastic bending, while also achieving darker and more saturated colours than previously possible with the use of only traditional pigmentation.