Numerical Study: Substrate Thickness and Type of Roof Structure and Their Impact on the Thermal Behavior of Green Roofs

The aim of this article is to provide a parametric analysis of the thermal behavior of green roofs, focusing on the influence of the thickness of the vegetation substrate and the type of supporting structure. The simulation model is implemented on the roof structure of an industrial hall in Dubnica nad Váhom, Slovakia, which was created and successfully validated based on real measurements of temperatures and climatic conditions during eight days in September 2023. After validating the model, a series of simulations of three structural variants was performed over three days in the summer. The results demonstrated that the greatest impact on reducing temperature fluctuations was achieved by increasing the thickness of the vegetation substrate (variant V2), which contributed to a reduction in heat flows fluctuations of up to 82% and caused a favorable phase shift in maximum temperatures. The introduction of a reinforced concrete supporting structure (variant V1) brought a partial improvement in the lower layers, while the combined variant (V3) demonstrated the best results—stabilization of temperatures and heat flows throughout the structure, eliminating overheating and cooling of the interior, and overall improvement in the thermal balance of the roof system. The results point to the high potential of green roofs in improving the thermal properties of buildings in summer conditions.