Current building envelope greening systems are not just areas covered with vegetation. Today’s systems can maximise the functional contribution of vegetation to a building’s performance and become part of a sustainable urban renewal strategy. The impact of the vegetation layer directly affects the building in its immediate vicinity, from the outside, while also having a significant impact on the indoor environment. Green roofs are the most widespread vegetated structures worldwide. This paper aims to demonstrate the behaviour of the temperature regime of an extensive green roof over a production hall and an administrative area in comparison to that of a roof without vegetation cover. In evaluating the results, a period with weather representative of winter and summer was selected to show the importance of seasonality. The fact that this is a new building, and that the extensive roof is not fully covered with vegetation, is very well reflected in the results, as the absence of a vegetated area significantly affects the temperature of as well as the heat flux through the roof structure. The dark colour of the substrate absorbs significantly more solar radiation than the light surface of the waterproofing, resulting in an increase in temperature and heat flux into the structure.

Urban population growth has resulted in land use changes and the replacement of many vegetated areas with hard dark surfaces. The altered surfaces warm the urban climate, a phenomenon known as the urban heat island (UHI) effect. Green systems such as vegetated facades significantly affect the outdoor microclimate through evapotranspiration cooling. In particular, the method of irrigation has a major influence on evaporation efficiency. This paper investigates the effect of an active vegetated façade irrigation system on the surface temperature behaviour of the envelope. The maximum difference between the surface temperature of the actively irrigated vegetation wall and the vegetation wall irrigated by hourly interval was almost 14°C. When comparing the surface temperatures of the actively irrigated vegetated façade with the non-vegetated façade - dark cladding, the maximum difference was almost 15°C. The difference between the surface temperature of the actively irrigated vegetated façade and the surface temperature behind the air cavity was almost 9°C. This reduction in temperature results in a shading effect of the vegetation wall. The use of vegetated structures is proving to be an effective tool and mitigation of temperatures in urban environments.

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.

Extensive green roofs (EGRs) are recognized as a promising passive cooling strategy due to their low areal mass, yet their thermal performance is strongly influenced by water availability. While prior studies have focused primarily on continuous irrigation or small-scale modules, the response of EGRs to temporary irrigation outages remains underexplored. This study presents a full-scale experimental investigation on an industrial roof segment in Dubnica nad Váhom, Slovakia, conducted during summer 2024. The thermal behavior of an EGR was compared to a conventional reflective flat roof (RR) and a roof with a hydroaccumulative layer covered with photovoltaic panels (PV). The experiment analyzed an unplanned irrigation interruption and the subsequent recovery, selecting representative three-day intervals from each phase. During non-irrigated periods under peak solar radiation, evapotranspiration (ET) was minimal, resulting in increased heat flux into the interior. After irrigation resumed, ET accounted for nearly 70% of net solar radiation, reducing interior heat flux to 32% of the non-irrigated value. Heat gain reductions between irrigated and non-irrigated days were 1% for RR, 38% for PV, and 68% for EGR, correlating with energy consumed for ET. These results highlight that active irrigation substantially enhances the cooling performance of EGRs, demonstrating their potential as an effective adaptation measure for buildings under extreme summer conditions.

The green roof is an example of increasing the water retention in the urban areas and reduction of urban heat islands. The impact of green roofs and its influence on the thermal resistance or its change during the winter is often not taken into account in the contrary to the summer benefits. The surface of a highly insulated flat roof is overcooled during the night by the long wave sky radiation. This radiative cooling increases the thermal losses. This is reduced by the existence of additional green roof layers. Also, these green roof composition layers have their thermal resistance, which is usually not included within the calculation of thermal resistance using the EN ISO 6946. The thermal conductance of these layers is influenced by the water content, which is mostly higher than design values and hard to obtain. Also, the presence of snow in various forms on the roof can increase the resistance. In this paper, temperature courses during the winter season of the green roof, flat roof with gravel and the regular flat roof, based on the experimental measurement are analyzed. In this case, the use of green roof kept the temperature of the membrane almost constant near 0 °C during winter without correlation to the outdoor air temperature.

Urban areas increasingly face summer overheating, highlighting the need for passive cooling strategies. Extensive green roofs offer cooling potential, but the individual roles of vegetation and irrigation remain insufficiently quantified. This study addresses this gap through a controlled field experiment using a 2 × 2 factorial design combining vegetated and non-vegetated surfaces with irrigated and non-irrigated conditions. Surface and waterproofing membrane temperatures were monitored during dry conditions and a three-day irrigation period and compared with a meteorologically similar reference day. A factor-based decomposition approach was applied to quantify the contributions of vegetation, irrigation, and their interaction. Results show that vegetation alone provides limited cooling under dry conditions, while irrigation acts as the dominant cooling factor by increasing substrate moisture and thermal capacity. The combined application achieved the most effective performance, reducing the 90th-percentile waterproofing membrane temperature (T_M,90) by 8.51 °C relative to the non-vegetated, non-irrigated reference configuration. The proposed framework supports performance-based design of green roofs under summer heat stress.