# Phase Change Materials and Their Benefits in ETICS
## 1 Introduction
### Biotic Attack on ETICS Facade:  
Algae create an undesirable aesthetic effect on the facade surface. Most algae live in water, but some species also live in the air (_aerophytic algae_) and receive water in the form of rain or water vapor. Aerophytes are microscopic green or blue-green algae in our climate. On buildings, aerophytes live on wet and north-facing walls. If living conditions allow them, these microorganisms will multiply and form visible colonies (see Figure 2). Organic plasters, which form the surface layer of ETICS, are also suitable substrates [3; 12; 13].  
Figure 1: Algae on the facade of the External Thermal Insulation Composite System (ETICS) of a family house in Jesenik (CZ), north side. On the right side there is the composition of the system.  
Three conditions must always be met to create a growth:  
* Presence of algae.
* Sufficient moisture.
* Suitable substrate [3, 12, 13].  
According to a study [19, 20], the most common algae on facade plasters is an algae called _Cladosporium_ spp.  
The possibility of biotic infestation in connection with sufficient surface moisture depends on many factors such as ambient temperature, air flow and humidity, sunlight and orientation to the world sides and other factors. From this point of view, studies and research work were created focusing on the above-mentioned influences and the resulting possibilities of biotic attack on the facade and the growth of algae itself [5, 6, 7, 8, 9, 10, 11, 12, 13, 18, 21]. Thanks to this research, PCMs with the most suitable melting point of wax to reduce condensation on the ETICS surface were chosen for the practical part of our research, e.g., in the dissertation [18] the temperature of the facade surface in autumn 2007 (Brno, Czech Republic) was measured in the range between 0 and 30 \({}^{\circ}\)C. It was stated that the presence and retention of water on the surface of the ETICS is largely due to condensation on the facade compared to water in the form of rain. The spring and autumn months are especially critical due to temperature and relative humidity. Due to the limitation of humidity on the ETICS, it is therefore appropriate to prevent to a certain extent the possible condensation of water at temperatures between \(-5\) and \(+30\)\({}^{\circ}\)C [18].  
The case study of EMPA (Swiss Federal Laboratories for Materials Science and Technology) was also very interesting. [4] The results of this study gave the initial idea of dealing with PCM in connection with biotic attack. Temperature measurements were made on the north facing facade of the building. The outdoor air temperature was 5.1 \({}^{\circ}\)C. The sky was overcast. In addition to surface thermometers, a thermovision camera was also used. Measurements revealed that the windowless facade parts affected by algae were only slightly warmer than ambient at 5.5 \({}^{\circ}\)C. The measurements confirmed that the algae occurred only in the coldest areas of the facade [4].  
In a detailed examination of the areas covered with vegetation, the thermovision image revealed lighter spots. These spots hardly ever contained algae. ETICS metal anchors are located in the same place as these light spots. Thermovision measurements revealed that their influence as a thermal bridge caused a local increase of the facade surface temperature by 0.2-0.9 \({}^{\circ}\)C. This case study suggests that even a few tenths of a degree of Celsius can decide if the surface is attacked by algae or not. At only a slightly lower surface temperature, the moisture did not dry up quickly enough so that the water needed for algae growth was present. This explains the high susceptibility of ETICS to algae  
Figure 2: Algae on the facade of the ETICS of a family house in the village Lipová-lázne (CZ) with visible anchor points without attack due to the thermal conductivity of the anchor, north side.  
occurrence and the need for biocidal protection; the better the thermal insulation capacity, the cooler the facade surface [3; 4].