In the diploma thesis, the influence of the surface absorptivity factor of the finishing layer of flat roofs on the hygrothermal behaviour of different flat roof structures was analysed. Four structural roof types were considered: inverted flat roof, conventional warm flat roof, lightweight industrial roof and endoskeletal flat roof. The analysis was based on numerical simulations performed using the WUFI software, which enables time-dependent simulation of heat and moisture transfer in building structures while considering real climatic data. The results showed that for all analysed absorptivity factors, the effective thermal transmittance of the structures gradually decreased over time, indicating an improvement in thermal performance due to drying. Higher absorptivity factor values increase the absorption of solar radiation, which leads to higher surface temperatures and more intensive drying of the structure. Consequently, higher absorptivity factors resulted in lower final moisture content values and lower effective thermal transmittance values. The comparison of individual roof types showed significant differences in hygrothermal response, mainly due to the material composition of the structures and the initial moisture content. More massive structures exhibited higher initial moisture content and slower drying behaviour, while lightweight structures, due to lower mass and the presence of air cavities, showed faster adaptation to external climatic conditions. The overall conclusion of the thesis is that the absorptivity factor of the finishing layer represents an important parameter influencing the long-term hygrothermal stability of flat roofs. An appropriate selection of the finishing layer can, under certain conditions, contribute to improved drying of the structure, a more stable hygrothermal response and improved thermal performance of building structures.
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