Search

Green roofing technologies have been developed and implemented worldwide as they bring with them thermal, hydrological, and environmental benefits, especially in urbanized areas. Many studies have been conducted to investigate the thermal performance of green roofs over reinforced cement concrete (RCC) structural bases but there is a lacuna of experimental evaluation of the thermal performance of green roofs on sloping galvanized iron (GI) sheet truss type roof structures. In this paper, the thermal performance of a retrofitted extensive green roof is quantified; this is challenging in subtropical climates because of extreme seasonal and diurnal variations. The thermal performance of the green roof system was assessed using a life-size experiment setup followed by a whole-building simulation using Design Builder, which runs on the EnergyPlus simulation engine. Two prototype roofs were analyzed and the performance of the retrofitted extensive green roof was compared with that of a conventional RCC roof solution. To validate the results, two prototype buildings were constructed at a university campus and their thermal and energy performance analyzed for two observation periods, one during a typical summer week and the other during a typical winter week. The extensive retrofitted green roof displayed enhanced thermal and energy performance at a nominal additional cost. The findings of this study can be deployed in the development of a retrofitted extensive green roof module for sloped GI sheet roofs for better thermal performance, and hence reduced energy loads, and meet the sustainable development goals. [ABSTRACT FROM AUTHOR]

Sweet potato greens are an underused but highly nutritious vegetable that grows well in urban environments and could help alleviate food insecurity and related health problems. Therefore, trials were conducted in field rows and a green roof with seven varieties of sweet potatoes to determine whether 1) they differed in their production of greens and 2) harvesting greens influenced yield or nutrients of storage roots. There was no difference in the mass of sweet potatoes greens harvested among the varieties in either production system. Harvesting greens severely reduced the harvested mass of storage roots, although it increased the content of eight minerals in storage roots, including boron, calcium, copper, iron, phosphorous, potassium, sulfur, and zinc. Urban farmers may have to decide whether harvesting greens or storage roots are their primary objective if harvesting the former limits the latter. Future research should explore the timing of harvesting greens and the amount taken to see if different methods allow for a high yield of storage roots that are high in nutrients. [ABSTRACT FROM AUTHOR]

To renovate an ordinary building roof into an extensive green roof (GR), on the basis of optimizing the runoff process, the total runoff control rate (TR-CR) and peak runoff control rate (PR-CR) were analyzed with the SWMM model under parameter sensitivity analysis. The response surface method (RSM) was used to investigate the effect of area ratio (GR area to total roof area), width (surface width per unit), and soil hydraulic conductivity on TR-CR and PR-CR. The optimal test conditions were obtained through the establishment of quadratic regression equations. The results showed that the effects of the three factors on TR-CR were in the order of area ratio>hydraulic conductivity>width, and on PR-CR was area ratio>width>hydraulic conductivity. Considering the volume capture ratio (80%) of annual rainfall and construction cost of the GR, under the optimal conditions of the area ratio of 0.79, width of 2.21 m, and hydraulic conductivity of 55.59 mm/h, the average values of TR-CR and PR-CR for this optimization scheme were 80.2% and 80.9%, respectively. This result show that the multiple quadratic regression model established is reliable. Therefore, the RSM can effectively optimize the simulation parameters, and provide some theoretical and practical basis for the renovation or construction of GRs. [ABSTRACT FROM AUTHOR]

The availability of green space is decreasing along with the increase in population. Since then the land has been replaced by buildings as more people need a place to support human activities. As a result, the absorption of heat increases, causing the temperature in urbanized areas are higher relative to outlying areas (Urban Heat Island). Therefore, some efforts need to be made to reduce heat absorption, one of which is by applying the green roof. A strong roof structure and roof panel are required to implement green roofs. Wood is a material that has both strength and lightweight. However, the use of wood panels for roofing is not common in tropical areas due to the high rainfall. The wood roofing still has a potential to be used through the application of green roof technology that accommodate a waterproof layer and is not easily degraded by planting media. This study aims to examine the potential use of green roofs which made of wood structures and wood roofing in a tropical climate.

Urban Heat Islands (UHIs) are a growing concern in metropolitan areas due to the concentration of infrastructure, reduced vegetation, and increased human activities. The UHI effect results in higher temperatures in urban areas compared to rural surroundings, contributing to adverse environmental and health impacts. One of the promising mitigation strategies is the implementation of green roof technology. This paper investigates the potential of green roofs in reducing UHI effects by analyzing their thermal performance, vegetation characteristics, and energy savings. An experimental study was conducted on two types of green roofs: extensive and intensive, across three cities with varied climatic conditions. Results showed that green roofs could reduce the surface temperature by up to 5°C, resulting in significant reductions in building cooling demands. The study concludes that green roofs, particularly extensive systems, offer a viable solution for UHI mitigation while providing additional ecological and economic benefits.

Abstract Green roofs are promoted to contribute to more resilient cities by enhancing urban ecosystem services and food systems. Extensive, low‐maintenance green roofs experience frequent environmental stresses, which reduce plant survival and growth. Stress‐tolerant plants are therefore used to sustain well‐established services, such as building temperature regulation. However, transitioning extensive green roofs to provide other key urban services, such as food production, involves less tolerant plant species. Although facilitation exerted by stress‐tolerant species (nurses) has been proposed to improve the performance of stress‐intolerant species (protégés) in extensive green roofs, the conditions under which facilitation could occur are not well understood. Therefore, a comprehensive framework is needed that integrates current knowledge on how the performance of protégé species is affected by nurse plants across stress conditions. We present a framework for green roof research that results in a linear model that integrates (i) modern trait–environment theory and (ii) facilitation ecology in a refined stress‐gradient hypothesis (SGH) originally developed following study of other stressful environments. The model makes testable predictions on how phenotypic traits mediate the performance response of protégé species to nurse plants along stress gradients in extensive green roofs. This is not only useful for the analysis of eco‐physiological performance measures directly linked with multifunctionality and ecosystem services, but also demographic or ‘vital’ rates that drive species persistence and plant community maintenance. We discuss a range of applications related to key agricultural and ecological questions arising from contemporary extensive green roof research, such as enhancing conditions for crop production, weed management, plant invasions and biodiversity conservation. We also provide guidelines for the generation of appropriate data and for fitting this model using readily available statistical procedures. Our framework will allow researchers to assess under which environmental conditions nurse–protégé interactions are feasible. We expect the findings from such research to help develop strategies and guidelines for managing environmental conditions that optimize protégé performances that ultimately affect the delivery of ecosystem services in constructed urban green spaces.

Anthropogenic activities and climate change have a profound impact on the urban environment. Therefore, energy conservation is an important subject for city planners. Green roofs can provide building insulation and mitigate against the urban heat island effect. This research was conducted in Cyprus, comparing different types of green roof vegetation against a control roof with no vegetation and their concomitant effects on indoor temperatures. The research project was performed at Near East University Campus for duration of twelve months. The experiment consisted of three different green roof types, and each hut with green roof had 3.5 m2 roof areas with a soil depth of 8 cm. In addition, one control green roof system was established without insulation, without soil, and without vegetation. In order to measure the indoor temperatures of the huts, Elitech RC-5 temperature data loggers were used. The research results showed that green roof huts provided lower mean temperatures than the control hut during the summer period. Most importantly, huts with shrub plants had the lowest temperatures during hot summer conditions. Our results indicated that green roofs perform an important role in terms of building insulation and its subsequent energy use. [ABSTRACT FROM AUTHOR]

The development of green roofs to mitigate urban heat island effect is critical for conserving energy and reducing carbon footprint. This study evaluated the thermal performance of an extensive green roof design compared with a conventional roof and assessed the suitability of thirty-two plants for low-maintenance green roofs in a tropical area. Experiments were carried out in four phases, covering the tropical climatic conditions from June 2016 to December 2017. The results indicate that a green roof temperature was significantly lower than that of a conventional roof by 12 °C. This led to an 84 % reduction in heat transfer through the building, potentially leading to a decrease in electricity consumption by 0.20 kWh/m2/8 h and saving electricity costs by 0.019 USD/m2/8 h, achieved through a reduction in the cooling load on air conditioners. The highest carbon dioxide removal achieved in this study was 3.01 kgCO 2 /m2, with an effective mitigation of greenhouse gases by 28.46 kgCO 2 eq/m2/year. The top three plant species recommended for a low-maintenance green roof are Dracaena cochinchinensis, Santisukia kerrii, and Dracaena kaweesakii. The plant characteristics for low-maintenance green roofs in tropical climates include drought and extreme weather tolerance, disease and insect resistance, short and spreading roots, succulent leaves with ability to store water, low water requirements, slow growth rate, easy availability locally and affordability, thriving in low-nutrient conditions, and a high evapotranspiration rate. In applicable contexts, green roofs designed with suitable tropical plants could potentially enhance urban environments and contribute to achieving low-carbon and environmental sustainability. • Thermal performance of green roofs varies depending on the specific climatic conditions of the region. • Green roofs mitigate greenhouse gas emissions by reducing energy consumption. • Carbon dioxide removal by plants varies with solar radiation intensity. • Selection criteria for tropical plants are based on drought tolerance, sunlight, and watering requirements. [ABSTRACT FROM AUTHOR]

Studies on evapotranspiration (ET) by considering water retention layer have been rarely conducted. This study primarily aimed to examine the effect of vegetation treatment, substrate characteristics, and water retention layers on the ET characteristics exhibited by extensive green roofs. The present study was supported by the 5-month continuous field monitoring of the moisture content, actual daily evapotranspiration (AET), leaf area index as well as stomatal conductance values in 4 green roofs buckets. As indicated from the results, (1) the average AET of Sudem lineare (4.1 mm/day) exceeded that of Ophiopogon japonicus (3.3 mm/day) in a nearly 7 days of dry event. (2) Peat modified substrate and biochar modified substrate exhibited consistent water-movement behaviors. (3) The decrease in stomatal conductance of vegetation in water retention layer system was the minimal after the 13-day drying. (4) The declining rate of water content in the green roof sbustrate can be decreased by water evaporation from the water retention layer. Furthermore, the water retention layer system would begin to significantly facilitate the AET when the dry period exceeded 8 days in autumn. The AET rate can be increased by setting the water retention layer in green roof and it is 6 times higher in the autumn than that in the winter. [ABSTRACT FROM AUTHOR]

The construction methods of extensive green roof are different in different regional climate conditions, which are directly affected by weight load bearing capacity, planting substrate, plant species and other factors. In order to explore the planting types of extensive green roof suitable for warm temperate semi humid region, 12 plant species and 5 planting substrates were selected to conduct the experiment on the roof of the Architectural Art Museum (36°40'37"N, 117°11'25"E) of Shandong Jianzhu University, Licheng District, Jinan City, Shandong Province, China in March to October in 2019, and each plant species was planted on 5 planting substrates on the roof, respectively. By measuring the basic foundation layer load parameters, substrate bulk density and plant unit weight in the process of construction, the increase of planting weight load bearing capacity was calculated. After 4 weeks, the plant physiological indexes were tested. Finally, based on fuzzy mathematics subordinate function value method, combined with the plant physiological indexes, all combination types were comprehensively evaluated. The results showed that the unit weight of 12 plant species was divided into three categories, and the change trend of the weight load bearing capacity increase of each plant combined with the five planting substrates was similar to that of the five planting substrates. According to the comprehensive evaluation, 12 planting combinations were considered to be suitable for application on the extensive green roofs in warm temperate semi-humid areas. Compared with the plant weight, in the early stage of extensive green roof construction, the weight of planting substrate is the main factor leading to the change of weight load bearing capacity increase. [ABSTRACT FROM AUTHOR]

Due to substrate layers with different substrate configurations, extensive green roofs (EGRs) exhibit different rainfall runoff retention and pollution interception effects. In the rainfall runoff scouring process, nutrient leaching often occurs in the substrate layer, which becomes a pollution source for rainwater runoff. In this study, six EGR devices with different substrate layer configurations were fabricated. Then, the cumulative leaching quantity (CLQ) and total leaching rate (TLR) of NH4+, TN, and TP in the outflow of nine different depth simulated rainfall events under local rainfall characteristics were evaluated and recorded. Furthermore, the impact of different substrate configurations on the pollution interception effects of EGRs for rainfall runoff was studied. Results show that a mixed adsorption substrate in the EGR substrate layer has a more significant rainfall runoff pollution interception capacity than a single adsorption substrate. PVL and PVGL, as EGRs with layered configuration substrate layers, exhibited good NH4+-N interception capacity. The CLQ and TLR of NH4+-N for PVL and PVGL were − 114.613 mg and − 63.43%, − 121.364 mg, and − 67.16%, respectively. Further, the addition of biochar as a modifier significantly slowed down the substrate layer TP leaching effect and improved the interception effect of NH4+-N and TN. Moreover, although polyacrylamide addition in the substrate layer aggravated the nitrogen leaching phenomenon in the EGRs' outflow, but the granular structure substrate layer constructed by it exhibited a significantly inhibited TP leaching effect. [ABSTRACT FROM AUTHOR]

Agriculture in urban and urbanizing areas will be increasingly critical to enhancing food security and food sovereignty, creating income, strengthening social interactions, and improving health outcomes in cities. We used three roofs, a hydroponic system, an aquaponic system, and field rows in an urban environment to grow six dwarf tomato cultivars: 'Micro Tom', 'Red Robin', 'Sweet 'n' Neat', 'Terenzo', 'Tiny Tim', and 'Tumbler.' We measured the marketable yield and non-marketable yield, mass of non-marketable tomatoes exhibiting defects, and the content of 12 mineral nutrients in fruits. We found the productivity often varied among cultivars within a cropping system. 'Terenzo' and 'Tumbler' were always some of the most productive cultivars, whereas 'Micro Tom' was normally among the least productive cultivars. The production from 'Red Robin', 'Tiny Tim', and 'Sweat 'n' Neat' was more variable, sometimes producing high, moderate, or low mass. The mineral content was especially variable across the cultivars and we did not identify cultivars that were consistently high or low in mineral content across systems, indicating that the mineral content was highly influenced by a genotype x environment interaction. The amount of 5 minerals differed across cultivars in aquaponics, 9 differed in hydroponics, and 6–12 differed in the roof systems. A high-yielding cultivar should be selected first and production methods can then be modified to maximize the nutrient content. [ABSTRACT FROM AUTHOR]

Adsorption substrate in the substrate layer of an extensive green roof (EGR) is one of the most important factors affecting rainwater retention and pollution interception capacity. However, the contact time between runoff and adsorption substrate is extremely short in actual rainfall, and adsorption substrate cannot show fully rainwater retention and pollution interception capacity. So, selection of adsorption substrate based on its physical properties and theoretical adsorption capacity is unreliable. In this study, eight commonly-used adsorption substrate experimental devices are constructed with the same configuration. The delayed outflow time and runoff reduction rate of each device, along with event measurement concentration (EMC), average EMC, and cumulative pollutant quantity of SS, ammonium (NH4+), nitrate (NO3−), total nitrogen (TN), and total phosphorus (TP) in each device outflow under nine simulated rainfall events are measured and evaluated. The results indicate that vermiculite has a significant interception effect on NH4+ and TP with the advantages of low bulk density, high porosity, low cost, and a good rainfall runoff retention capacity under torrential rain and downpour events. In future practical engineering and related studies of EGR, attention should be paid to ameliorating the deficiencies of the adsorption substrates and optimizing their synergistic effects when combined with nutrient substrates.

Tehran is the capital city of Iran and its inhabitants are suffering from air pollution.Green roofs can be one of the choices to deal with this problem. In this paper, ability ofgreen roofs in absorbing four air pollutants (PM10, SO2, NO2, and CO2) in Tehran wasvaluated. First, the potential of 1 m2 of a hypothetical green roof in Tehran in absorbingPM10 and SO2 during 1 year was estimated using a dry deposition model. Absorbingpotential of green roof for NO2 and CO2 was taken from other studies. Next, the reductionof each air pollutant was valuated using replacement cost method. Then, results weregeneralized to the total roof areas of the residential buildings in Tehran for the green roofslife span. Estimations showed that value of green roofs covering an area of 94,093,625 m2in reducing PM10, SO2, NO2, and CO2 during 50 years in Tehran will be 506,361,775 $.

Hydrological response of anthropogenic soil systems, including green roofs, has crucial importance in many fields of water engineering and management. As a consequence, there is an increasing need for modelling of the anthropogenic soil systems behaviour. To obtain empirical data, two green roof test beds were established on a green roof of University Centre for Energy Efficient Buildings, Czech Technical University in Prague. Each test bed is 1 m2 in area and is instrumented for the runoff monitoring. One test bed was filled with less permeable local soil, the other with highly permeable commercial soil substrate, both were planted with stonecrops. Two simple deterministic lumped models - a nonlinear reservoir model and a linear reservoir cascade model - were used to assess the hydrological response of these green roof systems. The nonlinear reservoir model seems more appropriate for extensive green roof systems than the linear reservoir cascade model because of better description of rapid system reaction typical for thin soil systems. Linear reservoir cascade model frequently failed to mimic internal variability of observed hydrographs. In systems with high potential retention (represented by the test bed with local soil), episodically applied models that consider the same initial retention capacity for all episodes do not allow plausible evaluation of the actual episode-related retention. In such case, simulation model accounting for evapotranspiration between the rainfall events is needed.

Purpose: Implementation of green roofs could help to reduce rapid runoff and help cities to mitigate heat islands. The aim of the study is to assess the water and temperature regimes of four experimental green roof test beds having different growing media and plant coverage during the vegetation season 2018. Materials and methods: Experiments were conducted in four test beds (1 × 1 m) established on a flat roof. Two types of growing media were used. The first (A) was a substrate composed of crushed spongolite, crushed expanded clay, and peat. The second (B) was a coarser substrate, composed of crushed expanded clay, crushed bricks, peat, and compost. Two test beds, hereafter designated ACu and BCu, were filled with substrates A and B respectively and planted with a mixture of Sedum spp. cuttings with approximately 10% coverage. The substrate thickness was 6 cm. Two other test beds, designated ACa and BCa, were filled to a depth of 4 cm with A and B growing media, respectively, and planted with a carpet of Sedum spp. with approximate coverage of 100%. Results and discussion: The experiment was conducted over one growing season. Continuous monitoring of substrate temperature, water content, and outflow was conducted on each test bed. The lowest runoff coefficient was observed in test bed ACu, while the highest runoff occurred in test bed BCu, with twice the amount of outflow as ACu. The total runoff coefficient of ACa was more than one-third higher than that of ACu. The lowest maximum substrate temperature on the hottest day of the season was observed in bed ACa with a temperature of 40.6 °C, while the highest temperature was seen in bed BCu, 7.9 °C higher. Conclusions: The analysis of the rainfall-runoff relationship calculated for individual rainfall events demonstrated that runoff coefficients depended on initial water content, rainfall intensity, rainfall depth, substrate type, and vegetation cover. Beds planted with sedum carpets and having more extensive vegetation coverage were superior at moderating extremes of temperature. [ABSTRACT FROM AUTHOR]

Agriculture in urban and urbanizing areas will be increasingly critical to enhancing food security and food sovereignty, creating income, strengthening social interactions, and improving health outcomes in cities. We used three roofs, a hydroponic system, an aquaponic system, and field rows in an urban environment to grow six dwarf tomato cultivars: ‘Micro Tom’, ‘Red Robin’, ‘Sweet ‘n’ Neat’, ‘Terenzo’, ‘Tiny Tim’, and ‘Tumbler.’ We measured the marketable yield and non-marketable yield, mass of non-marketable tomatoes exhibiting defects, and the content of 12 mineral nutrients in fruits. We found the productivity often varied among cultivars within a cropping system. ‘Terenzo’ and ‘Tumbler’ were always some of the most productive cultivars, whereas ‘Micro Tom’ was normally among the least productive cultivars. The production from ‘Red Robin’, ‘Tiny Tim’, and ‘Sweat ‘n’ Neat’ was more variable, sometimes producing high, moderate, or low mass. The mineral content was especially variable across the cultivars and we did not identify cultivars that were consistently high or low in mineral content across systems, indicating that the mineral content was highly influenced by a genotype x environment interaction. The amount of 5 minerals differed across cultivars in aquaponics, 9 differed in hydroponics, and 6–12 differed in the roof systems. A high-yielding cultivar should be selected first and production methods can then be modified to maximize the nutrient content.

• The passive cooling effect of extensive green roofs during daytime is offset against their thermal insulation effect during nighttime. • Ipomoea batatas , as a non-CAM plant, significantly increases the passive cooling and weakens the thermal insulation effects of extensive green roofs. • Using 40% LECA increases the passive cooling and weakens the thermal insulation effects of extensive green roofs. The advantage of the high passive cooling effect of traditional extensive green roofs during daytime is always offset against their disadvantage of the high thermal insulation effect during nighttime in summer in subtropical regions. The purpose of this study was to develop types of green roofs that can not only improve the passive cooling effect of extensive green roofs during daytime but also mitigate the thermal insulation effect of extensive green roofs during nighttime in summer in humid subtropical regions to reduce the cooling energy load over 24 h compared with that of traditional extensive roofs. The following factors were considered to obtain such an ideal extensive green roof—the depth of growth medium, the proportion and placement of lightweight expanded clay aggregate (LECA), and the presence and absence of a non-CAM edible plant. The results indicated that, compared with the 0% LECA (traditional garden soil) roof without plants in the second stage and under a slightly different air temperature (0.26 °C during daytime and 0.57 °C during nighttime), the introduction of Ipomoea batatas and 10%–40% LECA can significantly increase the passive cooling effect by approximately 1.5 times (5.51–6.21 °C) during daytime and significantly mitigate the thermal insulation effect by approximately half (2.05–3.20 °C) during nighttime. In summary, the introduction of Ipomoea batatas (non-CAM edible plant) and LECA into the traditional extensive roofs can effectively reverse the higher-cooling-and-stronger-warming effects to higher-cooling-and-weaker-warming effects. [ABSTRACT FROM AUTHOR]

Purpose: Vegetative roofs (VRs) are fully planted roof spaces that offer aesthetic view, storm water management, sound insulation, energy savings, and air improvement. The aim on this work is to compare the life cycle environmental impacts of traditional gravel ballasted roof (TGBR) and extensive green roof (EGR) each having a surface area of 650 m2. Methods: Environmental impacts were determined and analyzed using a cradle to grave life cycle assessment (LCA) including two end-of-life scenarios (landfilling and recycling). In particular, for the use phase, the updated Lebanese electricity grid was integrated for the first time in the LCA software SimaPro and real-time temperature monitoring for TGBR and EGR roof mockups that were installed on the rooftop of the Chemical Engineering Building at the University of Balamand-Lebanon were used. Life cycle impact assessment was performed using the IMPACT 2002+ methodology for all impact categories except for water scarcity, which was determined from the water use in life cycle assessment (WULCA) consensus model. Results and discussion: Results demonstrated that the assembly and the use phase were the highest contributors to the environmental impacts for TGBR and EGR. Comparing the two types of roofs, TGBR had the highest contribution for all impact categories except for "land occupation." This is justified by the presence of the vegetation layer in the vegetative roofs. Conclusions: EGRs are more efficient than TGBR from an environmental perspective. Moreover, increasing the share of renewable energy in the total Lebanese energy production will lower greenhouse gases emissions from the energy sector and the other life cycle environmental impacts. [ABSTRACT FROM AUTHOR]

Usage of green roofs is a major technique for urban stormwater management. In this study, layered and mixed substrate green roof platforms, using perlite or vermiculite as adsorption substrates, were established to investigate rainwater retention and pollutant leaching. The platforms were subjected to 12 simulated rainfall events. The average rainwater retention of layered substrate with perlite (30.95% ± 17.20%) was significantly higher than mixed substrate with perlite (21.66% ± 12.91%). However, there was no significant difference in rainwater retention between layered and mixed substrates with vermiculite (p > 0.05). The layered substrate effectively controlled total phosphorus (TP), phosphate (PO4 3--P) and ammonia (NH4+-N) leaching and layered substrate with perlite also exhibited better chemical oxygen demand (COD), total nitrogen (TN) and nitrate (NO3- ––N) leaching control than the mixed substrate with perlite. The cumulative leaching masses of layered substrate with perlite were lower (COD: 44.77%, TN: 19.60%, TP: 45.51%, NH4+–N: 20.27%, NO3–N: 21.47%) than mixed substrate; the TP and NH4+–N cumulative leaching masses of layered substrate with vermiculite decreased by 51.49% and 25.34% compared with mixed substrate. Moreover, layered and mixed substrates with vermiculite showed better TP, NH4+–N and PO43-––P leaching control than perlite. The layered substrate improved pollutant leaching overall, but the selection of adsorption substrate plays an important role in the leaching control of green roofs. [ABSTRACT FROM AUTHOR]

Extensive green roof is one of the sustainable urban stormwater management alternatives to manage and mitigate the urban surface runoff. In order to implement green roofs more effectively, suitable plant species and substrate components for tropical climate must be identified. The aim of this study is to investigate the evapotranspiration (ET) behaviors in extensive green roofs based on different substrate types and local native plant species. Four green roof test beds containing pro-mixing pot and burn soils were each vegetated with Axonopus Compressus (grass) and Portulaca Grandiflora (sedum). A weather station with soil moisture sensors was installed to measure the weather and soil moisture data. The results showed that the mean ET rates for grass-pot soil, sedum-pot soil, grass-burn soil and sedum-burn soil were 1.32 ± 0.41 mm/day, 2.31 ± 0.72 mm/day, 1.47 ± 0.39 mm/day and 2.31 ± 0.43 mm/day, respectively. It is noted that environmental parameters such as ambient temperature, solar radiation and wind speed showed significantly positive relationship (p value < 0.01) with ET rates of green roofs except relative humidity. The crop coefficients (Ks) for the studied green roof plant species are estimated based on actual and reference evapotranspiration rates. The sedum planted in burn soil showed the highest crop coefficient (0.64), followed by sedum in pot soil (0.62), grass in burn soil (0.39) and grass in pot soils (0.37), respectively. The findings in this study also showed that substrate with better water retention capacity generally improved the Ks values.

Investigation of stress level might be facilitated also in plant and horticultural sciences, but currently mainly morphological parameters are in use. Antioxidant activity routinely measured in food-oriented researches and several studies indirectly indicated that stress factors can influence this parameter. Our aim was to assess the potential direct indicator role of antioxidant activity in stress conditions. We measured the effects of UVB and soil-delivered stress on Agaricus bisporus and Sedum hybridum. Our results indicate that UVB slightly decreases, while the inadequate soil conditions increase antioxidant activity; hence these measurements are suitable for determining the level of stress in different living samples.

Green roof is an important measure in "Sponge Cities" to reduce the runoff and improve the runoff quality. The runoff quantity and quality control capacity of five types of extensive green roofs (EGRs) were analyzed in Beijing for 51 nature rainfall events and 6 simulated events from July 2017 to October 2018. Different module scales (sizes) and substrate depths were examined to study their correlation to runoff retention, peak flow reduction, pollutant event mean concentration (EMC) and load reduction performance of EGRs. In general, both the single-field rainfall events and the long-term monitoring showed that as the module scale and substrate thickness increased, the retention capacity of the EGRs increased. As the module scale increased, the peak flow reduction rate (P frr) of the EGR modules increased, while the thickness of the substrate appeared to have less of an effect on P frr. When water quality effect was considered, compared with module scale, the substrate thickness had a more obvious effect on the average EMC of different pollutants. As the substrate thickness increased, the EMC of pollutants decreased. Under six simulated design rainfalls, EMC reduction rate of suspended solid (SS) of all types of EGRs ranged from 64.3%–73.1% while no reduction was found in the EMC of chemical oxygen demand (COD). The EMC trends of ammonia nitrogen (NH 4 +-N), nitrate nitrogen (NO 3 −-N), total nitrogen (TN) and total phosphorus (TP) were almost the same, and their EMCs decreased with increasing total rainfall depth. When the pollutant load was considered, the EGRs in this study were a sink of NH 4 +-N, NO 3 −-N, TN, and TP but a source of COD. Unlabelled Image • Runoff quantity and quality effect of extensive green roofs (EGRs) was conducted. • Both EGR scale and substrate thickness affected EGRs' runoff retention capacity. • EGRs had strong capacity to reduce concentration and pollutant load of SS. • The concentration of COD, N and P in EGR runoff was higher than that in normal roof. • The EGRs were the sink of TN, NH 4 +-N, NO 3 −-N and TP but the source of COD. [ABSTRACT FROM AUTHOR]

Rapid urbanization transforms permeable land into developed areas with predominantly impervious surfaces, significantly increasing stormwater runoff and exacerbating the risk of pluvial flooding. Green roofs provide an attractive strategy for increasing surface permeability by mimicking pre-development hydrologic functions and mitigating flood risks in compact cities. However, the potential of this strategy has not been rigorously assessed, despite advances in global stormwater management. This is mainly due to insufficient scientific knowledge of hydrologic performance and a lack of experimental studies of rainwater-harvesting capacity under specific climatic conditions. This study evaluated the hydrologic performance of a real-scale extensive green roof (EGR) constructed in a subtropical monsoon climate in Nanjing, China. Overall, the EGR showed considerable ability to retain rainfall (mean retention ~ 60%, accumulated retention ~ 30%), although retention performance varied from 11% to 100% depending on the rainfall event considered, and decreased with increasing rainfall. Event-based rainfall–runoff comparisons demonstrated that the EGR retained rainwater efficiently during the early stages of a rainfall event and significantly attenuated peak runoff flows compared to bare roofs. Statistical analysis showed that total rainfall depth, rainfall duration, and substrate layer moisture influenced the overall retention most strongly, but also the percentage retention and runoff depth, highlighting the impact of substrate properties in addition to rainfall characteristics on EGR hydrologic performance. These findings provide new knowledge of and important insights into the hydrological performance of green roofs in subtropical monsoon climates, which could be used to guide EGR construction to increase landscape permeability, mitigate the risk of pluvial flooding, and enhance the climatic resilience of urban regions. [ABSTRACT FROM AUTHOR]

Green roofing is a sustainable solution for building energy saving, urban heat island mitigation, rainwater management and pollutant absorption. The effectiveness and performance of green roofs depend on layer composition and properties. The uncertainties surrounding green roof performance modeling are mainly related to the vegetation and substrate layer, which are subjected to surrounding climatic conditions. Energy simulation software typically does not use validated models encompassing all possible combinations of vegetation layers and substrates. Therefore, the objective of this research is to investigate different extensive green roof solutions for assessing thermal performance and to provide information on vegetation and substrate layer design. Different simulations executed in EnergyPlus were carried out based on realistic literature data drawn from previous experimental tests conducted on plants and substrates. Several combinations (30 plant-substrate configurations, six vegetative species and five types of substrates) were defined and evaluated. Furthermore, indexes based on the surface temperatures of green roofs were used. Finally, a comprehensive ranking was created based on the scores to identify which extensive green roof combinations offered the highest performance. Greater plant heights, LAI values and leaf reflectivity values improve green roof energy performance in the summer more significantly than substrate modification. During the winter, thermal performance is more heavily dependent on the substrate if succulent vegetation is present, regardless of the substrate used. These results could provide designers with useful data at a preliminary stage for appropriate extensive green roof selection. [ABSTRACT FROM AUTHOR]

• Equivalent thermal performance indices of a green roof are determined. • Correlations between climatic parameters and thermal performance are analyzed. • The temperature profile inside green roof is S-sharp at non-air-conditioned state. • The bottom layer of the soil of the green roof act like a "cooling source". • Influence of the indoor critical air temperature on thermal resistance is discussed. Green roofs have shown a remarkable effect on the reduction of the building cooling load in summer. The assessment of the thermal performance of green roofs is essential for their design and evaluation. This study investigated the thermal characteristics of an extensive green roof under air-conditioned and non-air-conditioned states by using experimental data obtained on successive sunny summer days. Two indices of the green roof, namely the equivalent thermal resistance and the equivalent decrement factor, were estimated through comparison with a common bare roof. Under the non-air-conditioned state, the distribution of the average temperature on the green roof profile was S-sharp. The lowest average temperature of the green roof was observed on the interface between the planting soil and roof structure, which were 1.8 and 0.9 °C below the outdoor and indoor air temperature, respectively. This finding indicated that the bottom of the soil layer functioned as a "cooling source" that absorbed heat from the upside and downside. The indoor critical air temperature that maintains the heat flux equal to zero was investigated on the basis of the experimental data. The influence of indoor critical air temperature on the equivalent thermal resistance was discussed; for the same green roof under the same outdoor climatic conditions, an indoor air temperature that is closer to the indoor critical air temperature yields a higher equivalent thermal resistance. Therefore, the equivalent thermal resistance of the green roof obtained under low indoor air temperature is recommended for practical use. [ABSTRACT FROM AUTHOR]

Highlights • Vegetation surveys of extensive green roofs in Germany 20 years since installation. • The observed vegetation was defined by generalist (CSR) and stress-tolerator traits. • Half of the originally sown species that disappeared had competitive traits. • Colonising species comprised more than half of the observed cover. • Nine of the top 10 observed species were from original lists. Abstract Like any constructed ecosystem, the vegetation of extensive green roofs (EGRs) will change over time. Although this may influence the desired function and performance, little work has examined the floristic dynamism of EGRs over the long-term. Variations in species composition may be associated with original species (persistent or lost), colonisers (gained), or the effects of spatial heterogeneity. This paper reports on floristic variation of two unmanaged German EGRs twenty years after installation. To evaluate floristic change, the analyses focused on functional composition and plant strategies sensu Grime's CSR theory, referring to the basic adaptive strategies of competition, stress-tolerance and ruderality, and their derivatives. With reference to original documentation, less than half the original species persisted. In spite of the losses, both roofs had entire cover, or nearly so, thanks to colonising species. The generalist strategy (CSR strategists) was the most important functional trait in the observed vegetation, followed by stress-tolerance and then by variations in stress-tolerant ruderality. The functional composition of colonising species was chiefly ruderals, followed by stress tolerators and generalists. The drivers behind these changes relate to the pressures of stress, disturbance and competition, as well as spatial heterogeneity and strategies for dispersal and regeneration, seedbank and propagule sources. This study suggests that long-term floristic diversity may be facilitated by ensuring a diversity of traits and species from the start, by providing spatial heterogeneity, and by considering the mechanisms that support persistence and those which determine colonisation. [ABSTRACT FROM AUTHOR]

Hydrological response of anthropogenic soil systems, including green roofs, has crucial importance in many fields of water engineering and management. As a consequence, there is an increasing need for modelling of the anthropogenic soil systems behaviour. To obtain empirical data, two green roof test beds were established on a green roof of University Centre for Energy Efficient Buildings, Czech Technical University in Prague. Each test bed is 1 m² in area and is instrumented for the runoff monitoring. One test bed was filled with less permeable local soil, the other with highly permeable commercial soil substrate, both were planted with stonecrops. Two simple deterministic lumped models - a nonlinear reservoir model and a linear reservoir cascade model - were used to assess the hydrological response of these green roof systems. The nonlinear reservoir model seems more appropriate for extensive green roof systems than the linear reservoir cascade model because of better description of rapid system reaction typical for thin soil systems. Linear reservoir cascade model frequently failed to mimic internal variability of observed hydrographs. In systems with high potential retention (represented by the test bed with local soil), episodically applied models that consider the same initial retention capacity for all episodes do not allow plausible evaluation of the actual episode-related retention. In such case, simulation model accounting for evapotranspiration between the rainfall events is needed. [ABSTRACT FROM AUTHOR]

Although numerous examples of green roofs can be found in Turkey, limited research has been conducted on plant material and substrate type in this climate. Both plants and substrate are very important components in green roof design, it is essential to determine the proper substrates and plants in green roof systems for domestic green roof design. Two types of growing substrates: a commercial substrate consisting of crushed brick and clay (45%), pumice (45%), and organic matter (10%), and a recycled substrate including 90% coarse pumice (10-20 mm) and municipal compost (10%), were tested in three depths of 4, 7 and 10 cm. Tested plant species included Achillea millefolium, Armeria maritima, Sedum acre and Sedum album. Overall, the commercial substrate performed better than the recycled pumice. In addition, deeper substrates promoted greater survival and growth for nearly all species tested. Either A. maritima or A. millefolium survived in the recycled pumice at any depth, whereas they did survive when grown in the commercial substrate in greater than 7 cm and 10 cm, respectively. They both likely would require supplemental irrigation to be acceptable for green roofs in Istanbul or locations with a similar climate. Both Sedum species survived in all substrate types and depths. Information gained can be utilized by green roof professionals in the Istanbul region and in other parts of the world with a similar climate. [ABSTRACT FROM AUTHOR]

Highlights • Health condition of nectar plants depends on Sedum species as companion plants. • Substrate moisture influence on nectar plants growth, planted together with Sedums. • Effects of companion planting depend on growth forms and leaf traits of plants. • High nectar plant density affects shoot biomass and health condition negatively. • Companion planting with appropriate Sedums can improve green roof performance. Abstract Introducing nectar-producing plants to green roofs and other urban green infrastructure has been attempted to support pollinator activities. Green roofs can be drought-prone, placing limitations on the success of plant growth and nectar production in the absence of irrigation. Plant species differ greatly in water usage patterns, so companion planting with low and high water users has been proposed to increase performance of high water use species, including species important for urban pollinators. Additionally, crassulacean acid metabolism (CAM) plants such as Sedum tend to have low water usage and are reported to improve health condition of neighbors. However, Sedum species differ in morphological and physiological traits such as leaf shapes and the speed at which they switch to CAM, resulting in water usage differences during drought that could affect neighboring plants. This study quantifies the effects of companion planting with CAM plants (Sedum album , Sedum kamtschaticum) on nectar-producing plants (Fagopyrum esculentum , Trifolium repens), focusing on target plant growth form and leaf traits of neighboring Sedum. The health condition of F. esuculentum and soil water contents were improved significantly when they were planted together with S. album , which has small leaves and rapid CAM induction. Therefore, suppression of evapotranspiration of neighboring CAM plants could have positive effects on erect growth form nectar species. In contrast, the health condition of T. repens , which shows prostrate growth, was not affected by neighboring CAM plant species. Judging from these results, growth characteristics including leaf traits of neighboring Sedum and growth forms of the target plants could be important factors determining the effects of companion planting in urban green infrastructure. [ABSTRACT FROM AUTHOR]

Highlights • Plant performance on identical green roofs differed in cities 1000 s of km apart. • Climate altered plant survival, growth and phenology. • Canopy density higher in three species polyculture compared with monocultures. Abstract Green rooftops are installed in many climates worldwide to support urban ecosystem services. Across North America, green roofs often make use of the same limited set of plant species, but the effects of regional climates on the survival and growth of a core set of plant species has seldom been investigated. To identify the impact of climate on green roof plant performance, we installed an identical green roof system in three Canadian cities that experience different climate conditions: Calgary, Alberta; London, Ontario; and Halifax, Nova Scotia. The green roofs were monitored across three growing seasons for plant survival, plant height, and canopy density of three species grown in monoculture: Aquilegia canadensis , Sporobolus heterolepis , and Sedum spurium , and a mixture planting with all three species. Green roof vegetation canopy density, plant height and growth rates differed by city, plant species, substrate depth and planting type (monoculture or mixture treatment). Between sites, plant species exhibited different growth phenologies. Mixture treatments performed slightly better than monoculture plantings at each site in canopy density measures but were not significantly greater in plant height measures. The growth rate between years two and three was greatest for the mixture treatment, indicating greater potential for long term survival and performance of mixture plantings. The London, Ontario site, with a relatively moderate climate, supported the best green roof growth and performance compared to the cooler and drier Calgary and the rainier Halifax. [ABSTRACT FROM AUTHOR]

In this study, laboratory-scale green (e.g. living) roof platforms were established to assess the potential use of polluted river sediment in their substrate mixture. The mean runoff retention of the green roof platforms, which contained peat and/or river sediment, after 11 artificial rainfall events was >72%, significantly higher than traditional roofs. However, green roof platforms that had been filled with peat soil showed chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) leaching. Green roofs that had used river sediment showed good leaching control for COD, TN and TP. The cumulative leaching masses from the green roofs contained 30% (COD), 42% (TN) and 47% (TP) as much as the total leaching mass from traditional roofs, and the Cu, Zn, Cd and Pb leaching risk from green roofs when river sediments are used as part of a substrate mixture was relatively low. Despite some nutrient leaching in the initial phase of runoff from the green roofs, river sediment has the potential to be used as a substrate for extensive green roofs. [ABSTRACT FROM AUTHOR]

Extensive green roofs are urban construction systems that provide thermal regulation and sound proofing for the buildings involved, in addition to providing an urban heat island mitigation or water retention. On the other hand, policies towards reduction of energy consumption, a circular economy and sustainability are core in the European Union. Motivated by this, an experimental study was carried out to evaluate the environmental risk assessment according to release levels of polluting elements on leachates of different green roof substrate mixtures based on recycled aggregates from construction and demolition waste through (i) the performance in laboratory of two procedures: compliance and percolation tests and (ii) an upscaled experimental leaching test for long-term on-site prediction. Four plots were built on a building roof and covered with autochthonous Mediterranean plants in Córdoba, South of Spain. As growing substrate, four mixtures were used of a commercial growing substrate with different proportions of a fine mixed recycled aggregate ranging from 0 to 75% by volume. The results show that these mixtures were classified as non-hazardous materials according to legal limits of the Landfill Directive 2003/33/CE. The release levels registered in extensive green roofs were lower compared to the laboratory test data. This shows how laboratory conditions can overestimate the potential pollutant effect of these materials compared to actual conditions. [ABSTRACT FROM AUTHOR]

The rainwater retention and peak flow reduction effect of seven extensive green roof (EGR) modules were studied in Beijing under natural rainfall events from May to September 2015. Monitored EGR modules had a layer of vegetation widely planted in northern China and a substrate layer with a thickness of 20 or 50 or 100 mm. The EGRs effectively retained rainwater, and regression equations of the potential retention capacity as a function of rainfall depth were developed for five EGR modules, which show that generally the capacity decreased as rainfall depth increased. The EGR with Sedum lineare Thunb and 100 mm improved soil had relatively higher average retention capacity (61.8%) than others, but all EGR modules had similar retention for an extraordinary rainfall event of 114.4 mm. For rainfall events less than 15 mm, EGR modules had 100% rainfall retention most of the time. The reduction in peak runoff rate ranged from 30.8% to 85.4%. The EGRs with Sedum lineare Thunb using 20 mm improved soil and 50 mm either pastoral soil or ultra-low weight substrates have similar peak reduction (51.3-58.2%). The EGRs with Sedum lineare Thunb have better rainfall retention and peak reduction than EGRs with Angiospermae or Sedum aizoon L. [ABSTRACT FROM AUTHOR]

• The green roof's hygrothermal behaviour patterns are analysed through monitoring campaign. • Lightweight extensive sedum-covered green roof system shows a lower temperature profile respect to the traditional concrete tile widely used as a flat roof finishing. • The soil's water content influences hygrothermal performance and increases the attenuation potential during summer. • The lightweight green roof is a valuable technical solution easily integrable in renovation project of existing buildings. • The renovation case study represents a practical example of green roof technology integration in a real environment. Extensive green roofs are considered an effective energy conservation measure for increasing buildings' energy efficiency and reducing the heat wave effect in dense build environments. In this context the present work has a two-fold objective: the first is to test and analyse a commercial extensive lightweight green roof sample through an experimental monitoring campaign carried out in a hot climate during the summer time; the second is to provide a practical case study application showing the architectural integration of the extensive green roof technology for existing buildings. The experimental monitoring campaign has been set for analyzing the temperature levels of an extensive green roof compared with a traditional horizontal roof finished with cement tile. The temperature levels have been analysed through a set of sensors positioned at different levels to characterise the green roof response to the climatic forces during summer. The results show that the air temperature in proximity to the green surface (15 cm above the greenery) is warmer than the undisturbed ambient air temperature during the day and lower during the night by 2–2.5 °C. The soil substrate and the vegetative layer contribute to increase ambient air humidity levels. As expected, the evapotranspiration of the green layer increases during a typical sunny day resulting in more water content in the air above the vegetative level of about 4–8 %. The surface temperature of the ground below the vegetation layer and the temperature of the ground layer (8 cm deep) shows beneficial attenuation and time shift properties with respectively 12–15 °C and 3–4 h. Compared to the traditional cement tiles the green roof shows lower intralayer temperature with differences ranging from 6 to 8 °C. Moreover, the renovation case study represents a practical example of green roof technology integration in a real environment. The study has high replicability, and it is meant to be an interesting example for researchers and professionals to boost the green roof technology application for higher-quality built environments. [ABSTRACT FROM AUTHOR]

In times of rapid urbanization and climate change has drawn more attention to stormwater runoff to sewer systems. The phenomenon of flooding in urban areas have become increasingly common as a result of heavy rains. Sewage systems in such a short time are not able to accept such a large amount of rainwater flowing on the site, which we experience the phenomenon of rainfall flowing down the street in excessive amounts. The problem of such phenomena can be solved by the development of green roof technology. Even in its simplest form that extensive green roof is able to delay outflow, and store in its entirety falling falls on the area. Everything depends on the layers and the size of the roof. The research study presented at two mini green roof, an area of 1.44 m2. Both cases have different layers. One of them has a layer of non-woven filter layer, the substrate and vegetation. The second station is built of layers of drainage, filter layer, a layer of substrate and vegetation. For experimental purposes a rain shower were used for testing, which allows to calibrate the right amount of water at a specified time. In the research of precipitation 10, 15 and 20-minute tested. On the bench number 1 a reduction in the range of 48.9 to 97.5% was achieved. The second experiment stand showed a higher retention capacity ranged from 74.5 to 94.7%. We concluded that the use of extensive green roofs in cities can help reduce storm water runoff from impervious surfaces.

Green roofs are becoming a major nature‐based solution worldwide to reduce urban stormwater runoff. Runoff reduction and retention mainly depend on the hydrological characteristics of substrates and the water use strategies of plants. However, little is known about how plant species affect the hydrological performance of green roofs. Two commonly used succulent plants and four turfgrass species were investigated for their impacts on the hydrological performance and runoff reduction of green roof lysimeters under controlled conditions using a rainfall simulator. The results showed that two succulent plants (Sedum lineare and Callisia repens) did not make significant contributions to canopy interception in any of the four seasons and made only minor contributions to evapotranspiration (ET) water loss in autumn and winter, resulting in minor effects on runoff reduction by the green roofs. Festuca arundinacea contributed 47.4–116.7% of water loss via transpiration and 36.5% of runoff reduction under a 25 mm day−1 rainfall intensity in spring and 48.0% of runoff reduction under a 10 mm day−1 rainfall intensity in winter. Poa pratensis, Lolium perenne, and Agrostis stolonifera also significantly reduced runoff. Runoff reductions by extensive green roofs were mainly caused by ET rather than by their canopy interceptions. Plant shoot biomass and ET were the primary factors controlling the runoff reduction by extensive green roofs. Our results strongly suggest that the runoff reduction capacity of extensive green roofs can be greatly improved by selecting plant species with a higher shoot biomass and ET rate. [ABSTRACT FROM AUTHOR]

Climate changes which we are experiencing at the moment are affecting the entire globe. Serbia, as a developing country, is in the process of defining its own energy strategy and priorities when it comes to the problem of increased energy consumption in its building stock. Research shows that residential sector consumes the largest quantity of energy. The CO2 emissions present another big problem which is in a direct correlation with energy consumption. Green roofs have multiple positive effects on buildings and their surroundings which make them a desirable option for retrofitting roofs. The aim of this paper is to investigate thermal properties of chosen green roof system and its potential to positively influence energy consumption for heating buildings and therefore CO2 emissions trough refurbishing existing old flat roofs. The municipality of New Belgrade was chosen for this research for its unique urban characteristics - existence of large number of similar or identical buildings, which have same structural characteristics and similar surroundings. For the purpose of this paper, blocks 45 and 70 were chosen. Results of this research are applicable on all of the 132 buildings found at this location, which have total roof area of 90.990 m². By calculating energy quantity needed for heating the building with the existing roof and two hypothetical models, which have green roof, it was possible to quantify energy savings, which are in a direct correlation with CO2 emissions. A control roof was introduced in order to examine if the proposed green roof possesses better characteristics than a traditional solution, most commonly used in Serbia. Apart from energy savings, overall impact of the green roof on the CO2 reduction per building was calculated. By multiplying these results, we drew the conclusion that a project such as greening roofs of existing residential buildings in blocks 45 and 70 would have a noticeable effect on both the energy savings and CO2 emissions. [ABSTRACT FROM AUTHOR]

To investigate nutrient leaching from extensive green roofs, green roof platforms were established to investigate the effluent quantity and quality during artificial rainfall. When the influent volume reached three times the empty bed volume, for which the cumulative rainfall was around 300 mm, the effluent TP and COD concentrations of green roof platforms filled with peat soil did not tend to stabilize. For a long-term operation, the substrate depths had little significant influence on TN, TP and COD concentrations of the green roof effluents. A normalized cumulative emission process method was proposed to discuss the difference in various pollutant leaching processes. Obvious differences in the leaching process of different contaminants for green roof platforms filled with various substrates were observed. For the green roof filled with modified substrates, the nitrogen and phosphorus pollutant leaching rates were relatively high in the initial stage of green roof operation and the phosphorus leaching rate was higher than that of nitrogen. The green roof is a sink for TN, but not for TP and COD in this study. The outcomes are critical for the selection of green roof substrates and also contribute to green roof maintenance. [ABSTRACT FROM AUTHOR]

Current research has validated the purification of rainwater by a substrate layer of green roofs to some extent, though the effects of the substrate layer on rainwater purification have not been adequately quantified. The present study set up nine extensive green roof experiment combinations based on the current conditions of precipitation characteristics observed in Shanghai, China. Different rain with pollutants were simulated, and the orthogonal design L9 (33) test was conducted to measure purification performance. The purification influences of the extensive green roof substrate layer were quantitatively analyzed in Shanghai to optimize the thickness, proportion of substrate, and sodium polyacrylate content. The experimental outcomes resulted in ammonium nitrogen (NH4+-N), lead (Pb), and zinc (Zn) removal of up to 93.87%, 98.81%, and 94.55% in the artificial rainfall, respectively, and NH4+-N, Pb, and Zn event mean concentration (EMC) was depressed to 0.263 mg/L, 0.002 mg/L and 0.018 mg/L, respectively, which were all well below the pollutant concentrations of artificial rainfall. With reference to the rainfall chemical characteristics of Shanghai, a combination of a 200 mm thickness, proportions of 1:1:2 of Loam: Perlite: Cocopeat and 2 g/L sodium polyacrylate content was suggested for the design of an extensive green roof substrate to purify NH4+-N, Pb and Zn. [ABSTRACT FROM AUTHOR]

Extensive green roofs are a promising type of urban green that can play an important role in climate proofing and ultimately in the sustainability of our cities. Despite their increasingly widespread application and the growing scientific interest in extensive green roofs, their aesthetics have received limited scientific attention. Furthermore, several functional issues occur, as weedy species can colonize the roof, and extreme roof conditions can lead to gaps in the vegetation. Apart from altering the function of a green roof, we also expect these issues to influence the perception of extensive green roofs, possibly affecting their acceptance and application. We therefore assessed the preferences of a self-selected convenience sample of 155 Flemish respondents for visual aspects using a discrete choice experiment. This approach, combined with current knowledge on the psychological aspects of green roof visuals, allowed us to quantify extensive green roof preferences. Our results indicate that vegetation gaps and weedy species, together with a diverse vegetation have a considerable impact on green roof perception. Gaps were the single most important attribute, indicated by a relative importance of ca. 53%, with cost coming in at a close second at ca. 46%. Overall, this study explores the applicability of a stated preference technique to assess an often overlooked aspect of extensive green roofs. It thereby provides a foundation for further research aimed at generating practical recommendations for green roof construction and maintenance. [ABSTRACT FROM AUTHOR]

Extreme weather events caused by climate change intensify the heat island effect, and a lack of greenery in urban areas increases the psychological stress and anxiety of city dwellers. This study compared the temperature reductions and heat amplitude reductions provided by four types of green roofing that can cover bare rooftops. The four types of plants grown on extensive green roofs in this study were: shrubs, perennial herbs, vines, and groundcover; these are potentially healing plants. Furthermore, this study investigated the effects of air temperature, relative humidity, and solar radiation on temperature reduction of the rooftop. Four-stage field experiments under various ambient temperatures were conducted on the roof of a typical residential townhouse in the Taichung metropolitan area, in central Taiwan, which has a warm oceanic climate/humid subtropical climate (Cfa). The results indicated that the bottom temperature of the perennial herb, shrub, vine, and groundcover green roofs were lower than the bare rooftop temperature by 17.75 °C, 12.57 °C, 11.55 °C, and 9.31 °C, respectively. The heat amplitude reductions of the bare rooftop were defined as 1 minus the result of dividing the experimental temperature fluctuation by the rooftop temperature fluctuation; the heat amplitude reductions attributed to the shrub and perennial herb green roofs were similar (83.32% and 82.58%, respectively); smaller reductions were produced by the vine (79.78%) and groundcover (74.88%) roofs. Moreover, air temperature and solar radiation were positively related to temperature reduction of the bare rooftop, and relative humidity was negatively related to temperature reduction. Finally, plants in extensive green roofs can further reduce the surface temperature of a bare rooftop when compared with that of bare soil roofs. [ABSTRACT FROM AUTHOR]