Search Results (138)

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. Full article

Green roofs are increasingly recognized as nature-based solutions that enhance urban resilience by supporting biodiversity, regulating microclimates, and mitigating stormwater runoff. However, their performance—particularly in extensive, lightweight systems—is often constrained by drought stress, which limits plant survival and ecosystem functioning under climate change. While substrate composition has been widely investigated in this context, the role of wind as a co-driver of drought impacts remains poorly understood. In this study, we examined how moderate wind interacts with substrate properties to shape drought responses in green roof vegetation. Using three non-succulent species (Plantago maritima, Pilosella officinarum, and Festuca rubra), we quantified substrate and plant water balance, physiological performance, wilting dynamics, and survival under prolonged drought conditions. Our results demonstrate that wind significantly accelerates drought effects—regardless of species or substrate—by intensifying substrate desiccation, with critical moisture thresholds reached at 6–8%. While wind alone did not impair plant performance under well-watered conditions, its interaction with drought markedly reduced survival time and increased physiological stress. Although general response patterns were consistent across species, subtle interspecific differences indicate that plant selection for green roofs should account for combined drought and wind exposure. These findings highlight wind as an overlooked but critical factor in the design and evaluation of resilient green roof systems and potentially contribute to a more comprehensive understanding of vegetation performance in urban nature-based solutions under climate stress. Full article

The reduction in energy demand in buildings through the adaptation of energy-efficient strategies is attracting significant attention from the research community. In this context green building concepts can contribute towards achieving national sustainable development goals (SDGs) and NetZero targets. Given the substantial energy demand associated with heating and cooling in commercial and residential buildings, enhancing energy efficiency has become essential for achieving sustainable development, particularly amid ongoing global energy challenges. The Envelope Thermal Transfer Value (ETTV) model has been established as a simplified method of calculating building loads; however, its integration with green building elements remains limited, particularly in subtropical climates. Furthermore, the combined effects of living walls, green façades, and green roofs on building energy performance have not been comprehensively investigated. In this study, an extensive experimental investigation was conducted using prototype buildings under controlled conditions to evaluate the thermal performance of green elements. Modified ETTV formulations incorporating green envelope systems have been developed, and the thermodynamic effects of these green elements on the building energy performance have been analysed. The results demonstrate that integrating green elements significantly reduces thermal heat gain and cooling energy demand. Specifically, a combination of a living wall on a west facing wall and a green roof could reduce the thermal heat gain by up to 30%. Full article

Growing urbanization influences the urban hydrological cycle by increasing stormwater runoff. Consequently, Stormwater Collection Networks may suffer troubling phenomena, such as pressurized flow conditions. One promising strategy to resolve this issue involves the adoption of green roofs. This study investigates the effect of green roof installation on the enhancement of sewer network behaviour. Numerical simulations were conducted using EPA SWMM 5.2. The model was varied by changing the hydraulic roughness and the slope of the drainage network conduits along with the green roof extension. Preliminary results revealed that green roofs can significantly mitigate the pressurization hazard in urban drainage systems. Full article

Extensive green roofs can be used to provide spaces for local agriculture in urban environments, although extreme moisture and temperature conditions typically found in these systems can often be challenging for crop production. The Southern Illinois University-Carbondale extensive green roof was utilized to determine the effects of a polyacrylamide hydrogel, pine bark mulch, and irrigation frequency on the growth and productivity of ‘Compact’ and ‘Italian Large Leaf’ basil (Ocimum basilicum), and the growth and overwintering ability of two perennial culinary herbs, sage (Salvia officinalis) and thyme (Thymus vulgaris). Results indicated that weekly irrigation increased late-season basil and perennial plant vigor, basil fresh and dry weight, and overwintered perennial plant vigor and height compared to bimonthly watering. Although the use of pine bark mulch improved basil fresh weight and plant vigor compared to no mulch, mulching did not influence (p > 0.05) perennial herb growth or overwintering in an extensive green roof environment. Hydrogel applications improved basil plant height compared to none, although fresh and dry plant biomass were not influenced by hydrogel applications. In comparison, hydrogels as additions to the green roof medium did not influence either early- or late-season perennial plant vigor, although the overwintered plant vigor collected the following spring was greater in the no-hydrogel treatment. For perennial herbs, sage had greater vigor, overwinter survival, and overall suitability for extensive green roof environments compared to thyme. This research indicated the importance of perennial herb selection and consistent water supply for annual and perennial herb growth and the overwintering success of perennial herbs. Thus, supplemental water and other management strategies to provide more constant medium moisture content are important considerations for sustaining culinary herb production on extensive green roofs. Full article

The University Botanic gardens Ljubljana has been planting vegetation on bus stop shelters in the capital city (Ljubljana) of Slovenia since 2020. The aim of the project is to create a green network across the city, contributing to the conservation of plant biodiversity and providing food resources for pollinators throughout the entire growing season. The plantings were designed exclusively with native plant species, naturally occurring in the territory of Slovenia, flowering from early spring to late autumn. The selected species are also horticulturally attractive, forming small extensive green roof gardens that mimic karst rock ledges, where plants are adapted to drought, shallow soils, and strong sunlight exposure. In 2024 and 2025, monitoring was carried out on eight selected shelters, focusing on plant presence, changes in vegetation cover, and the occurrence of spontaneously sown species and invasive species. The results show that, even after five years without additional maintenance, all plantings are thriving and remain horticulturally attractive. A variety of species flower from early spring to early summer. During drought periods, flowering intensity decreases somewhat but does not cease; in autumn, the shelters green up again with autumn-flowering species. The project has been very well received by the public and is now firmly established in the city. Every year, between 10 and 20 new shelters are planted. By the end of 2025, a total of 75 bus shelters had been greened in all main directions from the city center towards the outskirts. Full article

Freshwater scarcity and saline groundwater are major constraints for maintaining green roofs in coastal areas. This study evaluated the response of Jacobaea maritima subsp. sicula, (Sicilian silver ragwort) a drought-tolerant coastal ornamental plant, to tap water and seawater irrigation under Mediterranean summer conditions. Plants were grown in 10 cm-deep green-roof modules and subjected to six irrigation regimes: tap water, seawater, or alternating tap water and seawater, each applied at 4- or 8-day intervals, with irrigation volumes equal to 60% of cumulative reference evapotranspiration (ET_o). Growth, relative water content (RWC), chlorophyll index (SPAD), and leachate electrical conductivity were monitored to assess plant performance and salinity responses. Seawater irrigation caused rapid substrate salinization, leaf dehydration, and plant death within one month, while alternating seawater with tap water also failed to sustain survival. In contrast, tap water–irrigated plants maintained high RWC, chlorophyll content, and stable visual quality throughout the experimental period, even with deficit irrigation at 60% ET_o every eight days. These findings demonstrate that J. maritima subsp. sicula is well suited for freshwater-irrigated extensive green roofs in semi-arid regions, providing reliable performance under infrequent irrigation and limited water supply. However, seawater or high-salinity irrigation should be avoided. Future research should explore mixed freshwater–seawater irrigation regimes with a higher freshwater proportion, aiming to reduce total freshwater consumption while sustaining plant survival and esthetic performance. Full article

This study evaluates integrated water-saving strategies in two school centres (SC1 and SC2) located in Bragança, Portugal, combining rainwater harvesting systems (RWHS), green roofs (GR), and the replacement of conventional taps with high-efficiency models. Water consumption patterns were analysed, and nine scenarios were simulated to assess their feasibility and economic performance. Scenario 1, which focuses on replacing conventional taps, achieved the highest short-term cost-effectiveness, reducing potable water consumption by approximately 30% and providing a payback period of about one year. Scenario 3, integrating RWHS into conventional roofs with efficient taps, demonstrated the greatest overall benefits, reducing potable water demand by up to 60% and generating annual savings exceeding €7000 + VAT, with payback periods of eight years for SC1 and seven years for SC2. In contrast, scenarios involving extensive GR significantly reduced stormwater runoff but required higher investments and presented longer payback periods, ranging from 17 to 42 years. Overall, the results indicate that combining low-cost efficiency measures with RWHS maximises potable water savings and supports sustainable water management, while GR implementation should be considered selectively, particularly when broader ecological and thermal benefits are prioritised. Full article

Rainfall retention and runoff detention are the key hydrological processes that reduce runoff from green roofs. This study aims to quantify and model the hydrological response of nine combinations of growing substrates and drainage layers for extensive green roofs. Retention and detention capacities were evaluated using laboratory column experiments under two extreme initial moisture conditions—air-dried (D) and field capacity (W)—and three rainfall intensities (30, 60, and 100 mm h⁻¹). Regardless of the substrate–drainage combination, retention capacity, W_R, was significantly higher under dry conditions than under wet ones. Under wet conditions and rainfall intensity of 30 mm h⁻¹ (30 W tests), the mean W_R value (5.2 mm) was significantly lower than those recorded at higher intensities (14.3 and 14.2 mm, for 60 W and 100 W tests, respectively). Detention capacity, W_D, was less influenced by initial moisture and rainfall intensity, with mean values ranging from 7.4 to 10.9 mm. The distinct hydrological responses of green roof columns in the two antecedent moisture conditions were attributed to contrasting infiltration mechanisms: capillary flow dominated under dry conditions, while gravity-driven preferential flow prevailed under wet conditions. The application of a simple reservoir-routing model revealed that the AgriTerram (AT)—expanded perlite (EP) combination achieved the greatest reduction in total outflow volume and peak runoff. Under wet initial conditions, no single configuration clearly outperformed the others. This study highlights how the combined use of simulated rainfall experiments and a reservoir-routing model enables the identification of the most effective combination of substrate and drainage system to improve the hydrological performance of green roofs. Full article

Urban school environments often face significant thermal discomfort due to extensive paved surfaces, limited vegetation, and outdated building designs. This study examines how green spaces can mitigate temperature extremes and improve thermal comfort at two secondary schools in Coimbra, Portugal: Escola Secundária José Falcão (ESJF) and Escola Secundária D. Dinis (ESDD). Using a mixed-methods approach that combined school community surveys with on-site microclimatic measurements, we integrated user feedback on comfort with data on temperature and humidity variations across different indoor and outdoor spaces. Results revealed that tree-shaded areas consistently maintained lower air temperatures and higher relative humidity than unshaded zones, which experienced intense heat accumulation—up to a 5 °C difference. At ESJF, the older infrastructure and large asphalt surfaces led to severe heat retention, with east-facing classrooms recording the highest indoor temperatures. ESDD’s pavilion-style layout and existing green spaces provided comparatively better thermal conditions, although insufficient vegetation maintenance and limited shade reduced their effectiveness. The findings demonstrate a clear correspondence between the school community’s perceptions of thermal comfort and the measured microclimatic data. Vegetation—particularly deciduous trees—plays a critical role in cooling the school microclimate through shading and evapotranspiration. Strategic interventions such as expanding tree cover in high-exposure areas, installing green roofs and walls, and carefully selecting species can significantly reduce temperature extremes and improve outdoor usability. In addition, fostering environmental education and participatory co-design programs can encourage sustainable behaviors within the school community, underlining the importance of inclusive, nature-based solutions for climate adaptation. This research highlights that integrating green infrastructure in school design and management is a cost-effective strategy for thermal regulation. Green spaces, when co-designed with community involvement, not only enhance climate resilience and student well-being but also contribute to broader sustainable urban development goals. Full article

This paper presents a novel model for the year-round simulation of evapotranspiration (ET) and substrate temperature on two fundamentally different extensive green roof types: a conventional drainage-based “Economy Roof” and a retention-optimized “Retention Roof” featuring capillary water redistribution. The main scope is to bridge the gap in urban climate adaptation by providing a modeling tool that captures both hydrological and thermal functions of green roofs throughout all seasons, notably including periods with dormancy and low vegetation activity. A key novelty is the explicit and empirically validated integration of core physical processes—water storage layer coupling, explicit rainfall interception, and vegetation cover dynamics—with the latter strongly controlled by plant area index (PAI). The PAI, here quantified as the plant surface area per unit ground area using digital image analysis, directly determines interception capacity and vegetative transpiration rates within the model. This process-based representation enables a more realistic simulation of seasonal fluctuations and physiological plant responses, a feature often neglected in previous green roof models. The model, which can be fully executed without high computational power, was validated against comprehensive field measurements from a temperate climate, showing high predictive accuracy (R² = 0.87 and percentage bias = −1% for ET on the Retention Roof; R² = 0.91 and percentage bias = −8% for substrate temperature on the Economy Roof). Notably, the layer-specific coupling of vegetation, substrate, and water storage advances ecological realism compared to prior approaches. The results illustrate the model’s practical applicability for urban planners and researchers, offering a user-friendly and transparent tool for integrated assessments of green infrastructure within the context of climate-resilient city design. Full article

Extensive green roofs (EGRs) are increasingly recognized as multifunctional components of urban green infrastructure. In recent years, interest is growing in the use of native grassland species as alternatives to conventional green roof plants, both to enhance ecological function and to support biodiversity conservation. This study evaluated the performance of six native grassland species on extensive green roofs by assessing their growth characteristics (cover, survival, and flowering) throughout a single growing season (May–November 2024). We used three different substrates that differed in nutrient level: a nutrient-rich reused substrate, a mixed substrate, and a nutrient-poor perlite-based substrate. The results indicated that most species successfully established across all substrate types, although patterns in growth and mortality varied. Substrate nutrient levels strongly influenced early growth, but their long-term effects may diminish as nutrient dynamics stabilize over time. These findings suggest that native grassland species represent promising alternatives to conventional green roof plants in Japan, with several species showing strong adaptability to EGR conditions. Substrate nutrient management is essential for balancing plant growth, biodiversity, and maintenance requirements. This study contributes to improving the ecological performance and long-term sustainability of green roofs in urban environments. Full article

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. Full article

Urban areas face significant challenges from heat islands, stormwater, and air pollution, yet green roof adoption is hindered by feasibility and economic uncertainties. This study proposes an integrated framework to optimize green roof strategies for urban sustainability. We combine deep learning for rooftop suitability screening, comprehensive ecosystem service valuation, life-cycle cost–benefit analysis under varying policy scenarios, and ENVI-met microclimate simulations across Local Climate Zones (LCZ). Using Dalian’s core urban districts as a case study, our findings reveal that all three green roof types (extensive, semi-intensive, and intensive) are economically viable when policy incentives and ecological values are fully internalized. Under the ideal scenario, intensive roofs yielded the highest long-term returns with a payback period of 4 years, while semi-intensive roofs achieved the greatest cost-effectiveness (BCR = 4.57) and the shortest payback period of 3 years; extensive roofs also reached break-even within 4 years. In contrast, under the realistic market-only scenario, only intensive roofs approached break-even with an extended payback period of 23 years, whereas extensive and semi-intensive systems remained unprofitable. Cooling performance varies by LCZ and roof type, emphasizing the critical role of urban morphology. This transferable framework provides robust data-driven decision support for green infrastructure planning and targeted policymaking in high-density urban environments. Full article

Integrating photovoltaic (PV) systems with green roofs presents a synergistic approach to urban sustainability. Many existing flat-roof PV installations, often east–west oriented with limited elevation, present integration challenges for green roofs and are therefore understudied. This study addresses this by investigating the microclimatic effects of retrofitting an extensive green roof beneath such an existing PV array. Over a two-year period, continuous measurements of sub-panel air temperature, relative humidity, and module surface temperature were conducted. Results show that the green roof reduced average midday sub-panel air temperatures by 1.7–2.2 °C, with peak reductions up to 8 °C during summer, while nighttime temperatures were higher above the green roof. Relative humidity increased by up to 8.1 percentage points and module surface temperatures beneath the green roof were lowered by 0.4–1.5 °C, though with greater variability. Computational fluid dynamics simulations confirmed that evaporative cooling was spatially confined beneath the panels and highlighted the influence of structural features on airflow and convective cooling. Despite limited vegetation beneath the panels, the green roof retained moisture longer than the gravel roof, resulting in particularly strong cooling effects in the days following rainfall. The study highlights the retrofitting potential for improving rooftop climates, while showing key design recommendations for enhanced system performance. Full article