Caution: Strong Colors

The individual appearance of a facade depends on the color and structure.

With materials, structures and colors it is possible to create unique pieces and individual surfaces that express the personal style of the residents. The trend is currently the desire of many builders for a strongly colored, dark and intensely colored facade or partial areas. The decisive factor for whether a plaster is suitable is its reflection behavior - the TSR value. When using intensive shades, it should be noted that dark shades heat up more. This can be a problem with sensitive plaster surfaces. There is always a tension field in plaster layers, which is evenly distributed over the surface. A major influencing factor is a thermal or a moisture change. Extreme situations arise, for example,when the facade surface facing west is heated up by the sun's rays. A spontaneous thunderstorm causes rapid cooling on the facade surface, which leads to a high tension field in the plaster layer. If the whole thing takes place on a plaster base made of insulating material or on highly porous lightweight masonry, only a small amount of tension can be dissipated to the substrate. This means that there are strong power distributions in the plaster structure that can generate cracks in the relaxation phase. The resulting damage patterns are known. They show up over flat crack patterns up to plaster flaking. Plaster detachments can also be seen in composite thermal insulation systems with polystyrene rigid foam panels. An EPS insulation material begins to melt from approx. 70 ° C,so that the contact surface with the plaster layer is lost at higher temperatures.

In the standard version, when carrying out plastering work on an ETICS system or lightweight masonry, the lightness value (HBW) of the color tone must not fall below 20. The light reference value expresses the brightness of a color compared to a black point (= 0) and a white point (= 100). The HBW can be measured with an optical color measuring device with which the color tone to be defined is compared with a black and a white point. The lightness value shows the feeling of brightness of a hue in the light wave range of approx. 400 - 800 nm visible to the human eye. The HBW does not take into account the near infrared range (approx. 800 - 2500 nm) and the ultraviolet range (approx. 100 - 400 nm). The entire solar radiation must be taken into account for the thermal heating of facade surfaces. This consists of approx. 3% ultra violet, approx. 39% visible radiation and approx. 58% infrared. The degree of total solar radiation (total solar reflectance) can be determined using another measurement method. This is specified via the TSR value. The higher the TSR value, the more the solar radiation is reflected and the less the surface heats up. Another development is the targeted use of pigments, which show the lowest possible absorption of solar energy in the area of NIR (Near Infrared Radiation). As a result, lower surface temperatures can be made possible with the use of dark colors. Colloquially, the term "CoolPigments" has been coined for this generation of pigments. With this progress it is possible todayalso to use intensive color tones with a lower heating behavior on an ETICS or lightweight masonry thanks to special color recipes. It is important that a TSR value can only provide information about the actual layer structure, e.g. B. over a certain coat of paint with exactly this color formulation. The TSR value must therefore be determined individually for each paint and color and cannot be given as a blanket for all products. Subsequent tinting of the color with color concentrates on site also distorts the TSR value. For the contractor and the architect, this means that in the case of a color tint with an HBW below 20, the TSR value can be obtained from the manufacturer. By using the special pigments, TSR values can be presented in a range that is less critical for surface heating. Since the design variants differ from supplier to supplier when used on ETICS or lightweight masonry, the manufacturer should always be included in the consultation - also because with the use of a color shade under the HBW of 20 a difference to the generally known information sheets and Standards. A written recommendation for the use of the execution is issued in order to be able to provide a manufacturer's specification as a guarantee for a deviation from the regulations. Mode of action of the "cooling pigments". There is less absorption behavior compared to solar exposure. Incident light rays are reflected more strongly.

Diagram of the complete light spectrum. With the HBW value, the light waves are recorded in the visible range. The TSR value provides knowledge of the heating behavior of a surface over the entire light wave range.

Source: Baumit