Abstract
Liquid water present on the surface of façades is significantly responsible for microorganism growth. This issue became especially important with the increasing use of thermal insulation. The formation of condensation on these façades is often increased due to low surface temperatures [1]. Therefore, the development of a method for controlling the wetness and drying of façades is necessary, since no suitable method is yet available for this purpose. In this paper, the development of an active façade moisture detection system is presented. This system consists of a surface humidity sensor network based on reflection from infrared (IR) radiation, data acquisition and intelligent processing technology. The system is tested and calibrated in the lab for different textured surfaces. Different newly developed coating systems are tested in-situ using this method. These coatings are evaluated with respect to their surface condensation in order to identify the resistance against condensation. The method provides long-term non-destructive measurements of surface wetness. Targeted measures to prevent or reduce the growth of algae can be initiated with the obtained data. In addition, the measured data make a valuable contribution to the development of facade materials and coatings, which have improved drying properties and balance between hydrophilic and hydrophobic surface. As a result, the use of biocides to protect the facade from algae growth can be reduced.
Highlights
Biocide-free and algae growth resisting coating systems have been researched for years
Only the surface moisture is relevant for the microorganism growth and not the absorbed moisture of the coating system
Since the system works on a basic optical principle, the particular challenge of this work is to be able to measure all types of plaster and surface from smooth to rough, with a wide variety of colour and protective coatings under the most adverse environmental conditions with one device and without complex settings on site
Summary
Biocide-free and algae growth resisting coating systems have been researched for years. Long-term measurements are limited and possible only at accessible locations This method is inaccurate and can only determine the amount of surface moisture, but not the duration in which surface moisture is present. It was determined during the experimental series in RMI that the intensity of the reflected light depends on the surface moisture This correlation forms the basis for an optical detection of surface moisture. The transmitter is an infrared emitter that emits light in the wavelength range of 900nm on the test surface, which makes it possible to separate the measuring signal with optical filters from the daylight. The output signal of the light sensor must be evaluated; whereby higher surface moisture is assigned to a higher reflectance of the reflected light beam [3]
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