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The use of external thermal insulation systems (ETICs) is a powerful instrument in the energetic improvement of residential buildings. With that measure, the façade surface is thermally decoupled from the wall construction and consequently the humidity balance on the façade changes. This fact leads to better conditions for the growth of microorganisms. Therefore biocidal ingredients are often added to façade coatings. To evaluate the effectiveness and the durability of biocidal equipped façade coatings a comprehensive research project was conducted at the Holzkirchen branch of the Fraunhofer-Institute for Building Physics. 33 different types of façade coatings were applied to test specimen and exposed to real weathering conditions for five years. The general efficiency of the biocidal equipping of façade coatings could be proven. The development of biological growth on biocidal equipped façade coatings was significantly reduced, showing much less species than without biocide. Depending on the type of the coating, different biocides show a varying durability within the coatings. This has an influence on the species involved in the primary colonization. The biocide content in the coating itself allows no prediction of the susceptibility to biological growth. Façade coatings with biocidal paints showed better results than biocidal renders without additional paint coating

Durch Schlagregen können biozide Wirkstoffe, die zur Verhinderung bzw. Verzögerung des Bewuchses von Fassaden mit Algen und Pilzen eingesetzt werden, aus Fassadenbeschichtungen ausgewaschen werden. Seit ca. zehn Jahren werden die Wirkstoffe zunehmend auch in verkapselter Form eingesetzt. In einem einjährigen Freilandversuch wurde die Auswaschung der Wirkstoffe Terbutryn (2‐Methylthio‐4‐tert‐butylamino‐1,3,5‐triazin), Diuron (DCMU, 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea), IPBC (3‐Iodoprop‐2‐ynyl‐N‐butylcarbamat), OIT (2‐n‐Octyl‐isothiazolin‐3‐on) und DCOIT (4, 5‐Di‐chloro‐2‐n‐octyl‐isothiazolin‐3‐on) sowohl in freier als auch in verkapselter Form untersucht. Es zeigte sich, dass, eingesetzt in einem hoch wasserabweisenden Putzsystem, eine in ihrer Stärke an den jeweiligen Wirkstoff angepasste Verkapselung die Auswaschung deutlich – um bis zu 85 % bei Diuron – reduziert.Release of biocides from hydrophobic façade coatings: encapsulated vs. non‐capsulated biocide systems. Due to driving rain biocidal active substances, which prevent or delay the overgrow of façades with algae and fungi, can be leached out of the facade coatings. For the past 10 years encapsulated active substances are increasingly used. During a one year field trial the leaching of the substances Terbutryn (2‐Methylthio‐4‐tert‐butylamino‐1,3,5‐triazine), Diuron (DCMU, 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea), IPBC (3‐Iodoprop‐2‐ynyl‐N‐butylcarbamate), OIT (2‐n‐Octyl‐isothiazolin‐3‐one) and DCOIT (4, 5‐Di‐chloro‐2‐n‐octyl‐isothiazolin‐3‐one) have been investigated in capsulated and non‐capsulated form. It shows that a well adjusted rate of encapsulation of the active substances could significantly reduce the release (up to 85 % in case of Diuron) from highly hydrophobic façade coatings.

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