Green Roofs Research Articles

The Contribution of Green Roofs in the Achievement of Sustainable Development Goals

Green roofs are eco-friendly systems designed to deliver environmental, economic and social benefits while they enhance the aesthetic appeal of buildings. Their construction on rooftop of buildings in urban communities is important for the local residents and the environment. The Sustainable Development Goals are a set of 17 global objectives established by the United Nations in 2015 serving as a blueprint for developing a more sustainable, equitable and prosperous world by 2030, focusing on environmental, economic and social progress. The multiple benefits of green roofs are related with the achievement of the sustainable development goals. Creation of green roofs in urban areas facilitates the achievement of the SDG3 related with good health and well-being as well as SDG11 related with sustainable cities and communities, SDG13 related with climate action and SDG15 related with life on land. Therefore, the development of green roofs in urban areas is very useful and beneficial for the buildings’ residents, the environment and the local community. Due to multiple external benefits of green roofs their construction should be promoted with financial and non-financial incentives by municipal and regional authorities combined with removal of several barriers hindering their adoption and development.

The Shift Towards Green Construction: A Review of Environmental Management Strategies and Sustainable Materials in Developed Countries

Green materials have proven to be highly effective in managing environmental impacts when implemented in construction activities. The aim of this review paper is to critically examine the shift towards green construction practices in developed countries, with a focus on the integration of environmental management strategies and the use of sustainable materials. Currently, developed countries such as Switzerland, Japan, and China have significantly benefited their local environments by implementing these practices in the construction industry. Authorities and governments in these nations have taken proactive steps to establish standards and policies for the construction sector, encouraging more industries to participate in environmental management and protection efforts. The enforcement of rules and regulations in these developed countries has led the construction industry to prioritize environmental management and protection. The use of green materials in construction projects, including autoclaved aerated concrete blocks and green roof technology, has shown positive trends in advancing environmental protection and management. Developing countries are encouraged to adopt similar initiatives and utilize green materials in their construction industries to help secure the importance of environmental sustainability.

Is LCZ Enough? Physical Properties, Thermal Environments and Cooling Effects of Green Roofs in High-Density Urban Industrial Blocks

With rapid worldwide urbanization, the urban heat island (UHI) effect is becoming more and more serious. The UHI effect is more intense in industrial areas. Green roofs are an effective way to mitigate UHIs in high-density cities, which calls for thorough examination. This study explored the associations between the block characteristics and block thermal environment in high-density industrial areas based on the widely accepted Local Climate Zone (LCZ) scheme. The pedestrian air temperature comparisons before and after virtual green roof installations presented the cooling effects of green roofs. Thirty-six typical industrial blocks were involved in the study and the simulations were conducted utilizing ENVI-met. The results showed that (1) the air temperature in LCZ4 is significantly lower than those in LCZ2 and LCZ6, but no significant differences were identified between other pairs of LCZ types; (2) the cooling effect of green roofs significantly differs among LCZs, and is associated with sky view factor (SVF), average building area (ABA) and average building shape index (ABSI); (3) in high-density urban areas, additional functional parameters and building-volume indices should be included to better address the physical characteristics, thermal environment, and green roof cooling effect of industrial blocks. This study could improve the validity of LCZ classification for high-density industrial blocks and may provide direct implications for green roof planning.

Capacity Assessment of a Combined Sewer Network under Different Weather Conditions: Using Nature-Based Solutions to Increase Resilience

Severe weather conditions and urban intensification are key factors affecting the response of combined sewer systems, especially during storm events. In this regard, the capacity assessment of combined sewer networks under the impact of rainfall storm events of different return periods was the focus of this work. The selected case study area was a mixed-use catchment in the city centre of Thessaloniki, Greece. The hydraulic performance of the examined sewer network was assessed using an InfoWorks ICM model. The results indicated that mitigation strategies, such as the application of nature-based solutions (NBSs) or low-impact developments (LIDs) are considered essential for controlling combined sewer overflows. A multicriteria analysis was conducted to select the most appropriate NBSs/LIDs to be located in the study area to enhance the system’s capacity. The results of this multicriteria analysis were used to propose a combined sewer overflow mitigation scenario, based on the installation of green roofs, as the most highly ranked solution in the analysis performed. Incorporating the proposed NBS/LID in the hydrologic-hydraulic model significantly increased the performance of the studied combined sewer network.

Thermographic Analysis of Green Wall and Green Roof Plant Types under Levels of Water Stress

Urban green infrastructure (UGI) plays a vital role in mitigating climate change risks, including urban development-induced warming. The effective maintenance and monitoring of UGI are essential for detecting early signs of water stress and preventing potential fire hazards. Recent research shows that plants close their stomata under limited soil moisture availability, leading to an increase in leaf temperature. Multi-spectral cameras can detect thermal differentiation during periods of water stress and well-watered conditions. This paper examines the thermography of five characteristic green wall and green roof plant types (Pachysandra terminalis, Lonicera nit. Hohenheimer, Rubus tricolor, Liriope muscari Big Blue, and Hedera algeriensis Bellecour) under different levels of water stress compared to a well-watered reference group measured by thermal cameras. The experiment consists of a (1) pre-test experiment identifying the suitable number of days to create three different levels of water stress, and (2) the main experiment tested the suitability of thermal imaging with a drone to detect water stress in plants across three different dehydration stages. The thermal images were captured analyzed from three different types of green infrastructure. The method was suitable to detect temperature differences between plant types, between levels of water stress, and between GI types. The results show that leaf temperatures were approximately 1–3 °C warmer for water-stressed plants on the green walls, and around 3–6 °C warmer on the green roof compared to reference plants with differences among plant types. These insights are particularly relevant for UGI maintenance strategies and regulations, offering valuable information for sustainable urban planning.

BIM-based parametric energy analysis of green building components for the roofs and facades

Buildings are distinguished by their high energy demand over their lifespan. Iimproving energy efficiency in buildings necessitates mitigating the operation energy performance by evaluating more sustainable building components such as green infrastructures. The novelty herein is to conduct a BIM-based parametric energy analysis of green building components for the roofs and facades, taking into consideration the climate classification and orientation of the building. The proposed framework of this study uses Autodesk Revit software and Autodesk Green Building Studio as BIM tools, and Minitab software as a parametric analysis tool to estimate the energy performance of several alternative components based on Energy Use Intensity (EUI) and Annual Peak Demand (APD). A case study of a residential building is examined in four cities within different climate zones in Brazil; Rio de Janeiro (climate zone 08), Macaé (climate zone 05), Petrópolis (climate zone 03), and Nova Friburgo (climate zone 02). The base model design of components of the building includes a reinforced concrete roof and ceramic masonry façade. The utilized alternatives are roof components (i.e. green roofs and expanded clay roofs), and green façade. This work insight using green façade for all elevations and green roofs to enhance energy efficiency in terms of EUI by (10,17 %) in Rio de Janeiro, (6,67 %) in Macaé, (11,43 %) in Pertópolis, and (16,43 %) in Nova Friburgo. While the efficiency in terms of APD would be about (28,07 %) in Rio de Janeiro, (22,79 %) in Macaé, (21,67 %) in Pertópolis, and (12,58 %) in Nova Friburgo. When the construction project is designed to install a green façade to the main elevation only, this work recommends using green roofs rather than the expanded clay roof or the base model design roofs to increase energy efficiency in such types of buildings. This work contributes to integrating green building components into building designs to improve energy efficiency and empower decision-making and sustainability in buildings.

Comparative Evaluation of Evapotranspiration and Optimization Schemes for Green Roof Runoff Simulations Using HYDRUS-1D

The use of green roofs, a low-impact development practice, can be an effective means of reducing direct runoff in urban centers. Green roof modeling can enable efficient design by preliminarily grasping the behavior of the green roof system according to specific configurations. In this study, we aimed to find appropriate evapotranspiration and parameter optimization schemes for HYDRUS-1D, a commonly used modeling tool for green roofs. Comparative studies of this sort in the context of green roof runoff modeling have not been conducted previously and are important in guiding users to overcome the difficulties of choosing the right numerical schemes for an accurate prediction of runoff from a green roof. As a study site, the Portland Building Ecoroof in Portland, Oregon, USA, was chosen, as green roof configurations and observed data for climate and runoff were available. From the simulation results of the runoff volume, the Blaney–Criddle method, which was considered an alternative, was found to be appropriate for calculating evapotranspiration from a green roof (R2 = 0.82) relative to the Hargreaves method built in HYDRUS-1D (R2 = 0.46). In addition, this study showed that the optimization method using the harmony search algorithm, which was proposed as an alternative optimizer, was better (R2 = 0.95) than that of the HYDRUS-1D’s own optimization module (R2 = 0.82) in calibrating HYDRUS-1D for green roof runoff. The findings are thought to be useful in guiding modelers who are considering using HYDRUS-1D for green roof runoff simulations.

Measurement of Innovative Green Façades in the Central European Climate

Green structures, such as green roofs or green façades, are great examples of climate change mitigation. Their impact is mainly focused on roofs in the area of overheating reduction. In this paper, initial measurement results of a green façade experimental test setup are provided. The green façade uses an innovative board from recycled materials with vegetation rooted directly on the board. The tested green façade is divided into three segments. These segments differ from each other in their watering regimes, which are crucial for cooling effectiveness. Watering operates with the assistance of gravity; water flows from the top gutter through the boards. In this paper, these three segments are compared to each other with respect to temperatures on the surface of a regular external thermal insulation composite system façade (ETICS) during two summer days. The green façade showed an impact on the temperature in the ventilated air gap, where the temperature is almost the same as the outdoor air temperature in the morning with direct solar radiation on the façade and lower than the outdoor air temperature in the afternoon. At the peaks, the surface temperatures within the air cavity surface are up to 8 °C lower than those on a new white ETICS coating. This demonstrates a cooling potential, although the surface temperatures are always higher than the outdoor air temperatures during daylight hours.

Sustainable Water Management Through Green Infrastructure

This research explores the implementation of sustainable water management practices through green infrastructure (GI) solutions. As urbanization intensifies, traditional water management systems face challenges such as flooding, water pollution, and reduced biodiversity. Green infrastructure, which integrates natural processes into urban planning, offers innovative strategies for stormwater management, water quality enhancement, and habitat restoration. This study examines various GI techniques, including rain gardens, permeable pavements, and green roofs, assessing their effectiveness in mitigating urban water challenges. Case studies from multiple cities demonstrate the benefits of GI in promoting resilience against climate change while enhancing community well-being. The findings underscore the potential of green infrastructure as a viable alternative to conventional water management methods, advocating for its broader adoption in urban environments. Key Words: Sustainable water management, Green infrastructure, Stormwater Management, Urbanization, Climate resilience, Water quality enhancement

A Water-Energy-Carbon Nexus Approach for the Optimal Design and Configuration of Green Roofs and Photovoltaic Systems

A Water-Energy-Carbon Nexus Approach for the Optimal Design and Configuration of Green Roofs and Photovoltaic Systems

Influence of urban morphology on potential of green roofs in regulating local microclimate: A case study of Liège, Belgium

Urban microclimate varies for different urban morphologies in a city necessitating the assessment of impact of green roofs on the local microclimate in such typical morphologies. This paper explores the role of roof greening in regulating the local microclimate in Liège, Belgium, for nine realistic and unique urban morphological archetypes during a heatwave. The urban morphological archetypes are obtained based on a systematic data-driven approach using an extensive list of morphological parameters. Nine scenarios without green roofs and nine scenarios with green roofs are simulated using Solene-microclimat model. Green roofs are introduced only on the existing flat roofs identified using remote-sensing to analyse the realistic impact of roof greening. Our findings suggest that distinct morphologies in the archetypes result in distinctive impact of roof greening on these archetypes. For instance, green roofs can reduce surface temperature effectively in compact high-rise archetypes, whereas green roofs' potential to reduce air temperature is limited. While green roofs can effectively reduce surface and air temperature in compact low-rise archetypes, most compact low-rise archetypes are residential and have fewer flat roofs to green. However, large low-rise archetypes, which are predominantly industrial/commercial, can be retrofitted with green roofs, considering large potential of roof greening. This study provides insight into the interplay between urban morphology, realistic roof greening potential, and the UHI effect on local microclimate, improving our understanding of microclimate regulation with green roofs.

Maintenance, operational costs, and plant performance in three extensive green roof designs from Northwest México

Green roofs (GR) are nature-based solutions for climate change adaptation and mitigation in buildings and cities. However, few GR maintenance, installation, and challenge-solving guidelines are available for semiarid climates. We present how three case-study types of GR (urban gardens (UGR), native gardens (NGR), and wetland roofs (WR)) varied in installation costs, irrigation volumes, maintenance times, vegetation cover, survival, biomass and yield, in Ensenada, México, from 2022 to 2023. In UGR, nine edible species were cultivated to yield produce; in NGR, six native plants were planted, and four were grown in WR. UGR installation costs were 31 % and 21 % lower, but maintenance costs were four and 1.5 times higher than NGR and WR, respectively. UGR consumed 17 % more water annually than NGR and 42 % less than WR. Likewise, UGR demanded 94 and 92 % more annual maintenance time than NGR and WR. WR presented the highest survival, height, cover, and biomass values, followed by NGR (except for biomass) and UGR. Our results point to different GR solutions for distinct types of applications and users, demonstrating their versatility in design. All GR categories are suitable to reduce the ecological footprint of buildings; however, we emphasize that each GR design involves different economic, time, and challenge-solving commitments that should be considered before installation and operation.

Heating, cooling and energy management of cold climate educational built environments using green roofs

Educational spaces in the world with a student population of about 600 million people are significant energy consumers. Also, 66 percent of schools are among energy consumers in the lower categories of energy consumption management. Meanwhile, the world's student population is expanding while nonrenewable energy sources are running out. Recent investigations highlight schools’ focus on energy efficiency in construction, which is driven by escalating energy expenses and depleting resources. This study presents a model of green schools featuring green roof coverings interconnected with controllable window atriums, leveraging green architecture as a renewable energy solution. It assesses the impact of green roofs coupled with atriums on summer ventilation and winter heat control in cold climate regions, contrasting with conventional school designs. This study aims to improve the thermal performance of schools, reduce heat losses from the roof and walls of schools, and also help improve natural ventilation in classrooms. The research followed a descriptive-analytical approach and employed simulation techniques. The model is simulated using the Carrier HAP, and its analyses are validated by the U.S. Green Building Council's LEED certification. Then, a comparison is made between the thermal loads of the proposed model and the thermal loads of the conventional school model in this climate. The results demonstrate the advantage of using green roofs in improving thermal loads in winter and cooling loads in summer in classroom models with green roofs connected to atriums compared to classrooms with conventional 40 cm thick roofs or 66 cm thick roofs without greenery. Energy savings are achieved by creating schools with green roofs associated with atriums while maintaining students' connection with nature and utilizing this cover as an auxiliary learning space. Energy savings are 54.95 % in winter and 76.11 % in summer compared to conventional 40 cm thick roofs and 66 cm thick roofs without greenery.

Unirrigated Extensive Green Roofs in Humid Subtropics – Plant Selection and Substrate Design for Low Maintenance and Climate Resilience

Low-maintenance extensive green roofs hold the potential for adapting to climate change, but there is a limited understanding of their effective design in humid subtropical regions. In this study, we aimed to investigate low-maintenance green roof ecosystems capable of thriving under heat stress. Plant growth performance was evaluated in the second year of an experimental green roof in southwest China. This green roof was unirrigated and involved two plant communities (forbs and grasses) cultivated in four substrate types. Metrics of growth performance, including plant survival, green coverage, visual appearance, leaf stomatal conductance, and substrate volumetric water content were used to analyze the impact of substrate on plant growth. ESP substrate, comprising 30%v (percent of volume) expanded shale, 25%v perlite, 25%v vermiculite, and 20%v compost, featured the highest porosity and optimal growth of forbs, achieving an average green coverage of 66.76% and average visual appearance value of 3.56 throughout the monitoring period. The high total porosity of this substrate could be critical in facilitating root development and drainage. Moreover, during the summer’s heat and drought, while substrate water content is not a limiting factor for the survival of some established forbs, it remains crucial for the growth of grasses. Additionally, the same substrate impacts different plant communities variably. Four particularly well-performing forb species, namely Lycoris chinensis, Tradescantia pallida, Liriope muscari, and Salvia farinacea, demonstrated survival rates closed to 100% and an average visual appearance value exceeding 3 was noted, and thus, they are recommended as plant candidates for unirrigated green roofs. The distinguished performance of these species is attributable to their adaptation to heat and drought through specific physiological traits. Our findings provide insights into vegetation selection and substrate optimization for the successful establishment of extensive green roofs that can be feasibly developed without irrigation in the humid subtropical regions.

Carbon dioxide emission evaluation of biochar based vegetation concrete for ecological restoration projects

Vegetation concrete is increasingly being used for slope stabilization in highways, green roofing in urban developments, and erosion control in coastal areas due to its sustainable solutions for enhancing landscape aesthetics, mitigating pollution, and protecting the environment. However, the environmental and economic impacts of different mix proportions, particularly concerning CO2 emissions, remain insufficiently explored. This study aimed to identify the optimal mix proportions of vegetation concrete through laboratory testing that minimize CO2 emissions while ensuring compatibility with plant growth and cost-effectiveness. The vegetation concrete mix were prepared using different quantities of biochar (5 %, 10 %, and 15 %) and cement content (4 %, 8 %, and 12 %) by weight to evaluate their impact on porosity, unconfined compressive strength (UCS), alkalinity, plant compatibility, cost-effectiveness, and CO2 emissions from raw materials. The results indicate that increasing the biochar content from 0 % to 15 % led to a 16 % reduction in porosity and a 92 % increase in UCS of vegetation concrete. Similarly, increasing the cement content from 0 % to 12 % resulted in an 11 % decrease in porosity and a substantial 200 % increase in the UCS of vegetation concrete. Moreover, the addition of 5 % biochar had a beneficial effect on plant growth, however, increasing the biochar content beyond this level adversely impacted plant development. Based on laboratory test results, the recommended optimal mix for vegetation concrete includes a mix of 5 % biochar, 8 % low-alkaline sulfoaluminate cement, 6 % sawdust, and 6 % ferrous sulfate. The analysis of CO2 emission of the materials studied showed that cement contributed the most to CO2 emissions, followed by biochar, sawdust, water, and soil. Notably, the utilization of sulfoaluminate cement led to a 31.8 % reduction in CO2 emissions compared to Portland cement, while also lowering the overall cost of vegetation concrete by 24.7–33.8 %. This research underscores the necessity of scientifically establishing relationships between the composition of plant-based concretes and their environmental and economic performance. In summary, this study identifies optimal mix proportions for vegetation concrete, leveraging low-alkaline sulfoaluminate cement and biochar to minimize CO2 emissions, enhance landscape aesthetics, and ensure compatibility with plant growth, thus emphasizing its potential as a sustainable and cost-effective construction material.

Green buffer areas and green roofs: performance design to improve the urban water cycle

Abstract While in all Europe the land use does not decrease – contrary to EU soil strategy that would actualize the zero net land use by 2050 – cities are plagued by problems such as air pollution, urban heat island effect and uncontrolled run-off following intense rain events, which degrade the environment threatening the health and the safety of inhabitants. The impermeable materials and are responsible for the worsening of the urban water cycle and, at the same time, for the increase in summer air temperatures: both those effects can be mitigated by nature-based and draining solutions. The paper explains the hydrological phenomena of the urban impervious surfaces, highlighting the typical functional defects, providing then a list of various green technologies suitable to overcome the common issues of city centers like high density / reduced spaces, irreversible impervious surfaces, undersized drainage, presence of sub-structures / sub-systems, conservation of architectural heritage. The technical green solutions on the ground (bio-retention systems, rain gardens, trees, pervious pavements…) and on the roofs, specifically designed, behave 1) as a buffer for the stormwater and superficial run-off, being able to collect water, 2) as providers of side effects that can affect water quality, biodiversity, amenity in cities. Experimental results from a rain simulation are presented in order to argue potentials and limitations of these solutions, often narrated as salvific, or, on the contrary, underestimated in their technological specificities.

A study on the path planning and optimization of carbon peaking and carbon neutrality in the highway service area

The transportation sector is a major source of greenhouse gas emissions. Reducing emissions of the Highway Service Area (HSA) can help decrease the sector's carbon footprint and serve as a model for green transformation. Consequently, this study firstly employs the Life Cycle Assessment (LCA) to calculate the carbon emissions during the operational phase of a certain HSA in 2022, and then analyses the emission structure. Subsequently, four emission reduction pathways are identified, including Photovoltaic (PV) power generation, electrification retrofitting, forestry carbon sinks, and green roofs, in terms of both Three 100 Initiatives and carbon neutrality measures. On this basis, the planning of carbon peak and carbon neutral strategies for this service area under different scenarios are carried out, taking into account the dual carbon targets and relevant policies. The findings indicate that: (1) the HSA emitted approximately 766.84 tons of carbon emissions in 2022, with 96.53 % from purchased electricity. (2) PV power generation offers the optimal emission reduction benefits among four emission reduction pathways. (3) In carbon peaking scenarios, initiating PV construction is the optimal emission reduction strategy. (4) In most carbon neutrality scenarios, the simultaneous implementation of PV construction and bamboo planting can meet the neutrality requirements by 2060. However, if the HSA continues to develop economically after 2030, the economy could grow until 2035 to meet neutrality requirements. These findings can guide emission reduction strategies for other HSAs, accelerating the sector's transition to low-carbon emissions while supporting the development of policies for zero-carbon HSAs.

How green can it be? A methodology for calculating green roof retrofit potential in Valencia

Cities are accountable for more than 70% of global CO2 emissions and consume around 65% of the world's energy. In the pathway towards urban decarbonisation, nature-based solutions rise as a promising opportunity. They improve a city's resilience, stabilise temperatures and capture CO2, both mitigating climate change effects and adapting to them. This paper presents a novel methodology to assess the potential effects of green roof retrofit in urban areas, selecting suitable buildings for greening and estimating their decarbonising capacity. The proposed method combines the use of Geographic Information Systems (GIS) and artificial vision algorithms to select the roofs. Once selected, direct carbon sequestration and energetic savings are estimated based on empirical results. This methodology is successfully applied to the L'Illa Perduda neighbourhood of Valencia (Spain) as a case study. The GIS analysis shows that about 50% of the roofs' surface could be greened, directly absorbing around 350 tCO2yr−1 and reducing the energetic emissions of the neighbourhood in about 100 tCO2yr−1 by improving the insulating envelope of the buildings. The artificial vision computation selected 38% of the surface of the neighbourhood residential buildings.

Ruderal Plant Diversity as a Driver for Urban Green Space Sustainability

Urban development in south-eastern Europe has significant ecological consequences, such as a reduction in native plant diversity, the introduction of non-native species, and increased maintenance costs of urban green spaces. Achieving sustainable urban development requires a thorough understanding of the inventory of native plant species to better manage and conserve these areas. This study analyzed 806 vegetation surveys conducted in rural and urban areas over a 30-year period, identifying 450 plant species from 39 distinct plant communities. Our findings revealed generally low dominance index values in all communities, while Shannon diversity index values were particularly high, indicating rich species diversity despite urbanization pressures. Equality index values varied slightly, reflecting differences in species distributions. Principal component analysis (PCA) identified a substantial group of species with low abundance, which is essential for understanding and managing urban biodiversity. These findings have significant implications for urban planning and plant species conservation. Low dominance and high diversity suggest opportunities to improve urban green spaces by integrating diverse native species. In addition, the ecological and practical value of ruderal species, plants that thrive in disturbed environments, was emphasized, as well as their potential in medicine, phytoremediation, green roof design, and pollination services. Through directly correlating biodiversity indices with urban sustainability goals, our study provides useful insights for urban biodiversity management and the strategic integration of native plant species into urban landscapes.

Exploring the role of pedological and climatic aspects in the medium-term decline of green roofs hydrological performance: an experimental study in a Mediterranean environment

ABSTRACT In the realm of sustainable strategies for urban flooding risk mitigation, green roofs (GRs) emerge as a key solution. The complex relationship between hydrological, pedological, and climatic aspects poses several challenges in the definition of GRs’ medium-term behaviour, emphasizing the imperative for further research. Embedding pedological and climatological evidence, this study focuses on relevant observed changes in the hydrological performance and behaviour of two extensive GR test beds located in southern Italy over a 7-year monitoring period. Experimental rainfall and runoff data, at the event scale, point to a reduction of approximately 12% in the stormwater retention capacity (RC) of monitored GRs. Additionally, a comparative analysis of RC values in two specific time windows revealed how, in an early stage, it was controlled by soil moisture content whereas it is currently (aged state) mainly related to rainfall characteristics. After excluding climate variability as a potential driver for observed RC changes, a pedological experimental campaign highlights variations in the physical and hydraulic parameters of the peat substrate, which, in turn, is addressed to affect the retention and detention capabilities of the GRs.