Spectral optical properties and thermodynamic performance of reflective coatings in a mild climate zone

The article deals with optical properties and thermodynamic performance of reflective coatings applied on the vertical non-transparent external building surfaces. The starting point of this study comes from the fact, that there are various modifications of coatings, that their guaranteed properties can reduce heating and cooling loads with their application on external building surfaces. The paper presents the results of a comparative nature investigating the optical properties and thermodynamic performance of coatings containing hollow microspheres, as regards their impact upon the thermal properties of buildings envelope walls. The spectral laboratory and full scale outdoor testing methods were used and finally confronted in an experimental study. The tested samples were monitored by dynamic outdoor testing especially under clear sky in daytime and nocturnal conditions. Hollow microspheres coating and standard facing coating of acrylic base as a reference were analyzed primarily and confronted with materials of low-emissivity functions. As a result, the measured data demonstrate no differences in thermodynamic performance of the studied coating due to reducing heating loads especially for nocturnal conditions as well as their thermal emissivity parameters in comparison with the standard façade coating. On the other hand, coatings of hollow microspheres can contribute to the thermodynamic performance up to 5% in daytime conditions of predominantly insolated and weakly isolated walls due to reducing cooling loads in comparison with the standard façade coatings of an identical color shade.