Intensive Green Roofs Research Articles

Sustainable Construction in post-industrial Ursus district in Warsaw: Biologically Active Areas on Roofs and Underground Garages

Urbanization leads to the expansion of urban areas and increased population density, which has a negative impact on natural resources, including green spaces. To address these environmental challenges, various green measures and sustainable development practices offer environmental, economic and societal benefits. This article provides an overview of different types of green roofs, discusses their advantages and disadvantages, and outlines current legislation on biologically active areas in new residential developments. A residential project in the Ursus district of Warsaw was used as a case study to compare intensive and extensive green roofs. The project involved the installation of vegetation on the roof of an underground garage and later on the roof of the building, with detailed descriptions of the roof layers and vegetation used. One experiment examined seasonal variations in water runoff from green roofs. Three test sites simulated different seasons, with substrates in containers and vegetation watered twice daily. Results showed that spring, with temperatures around 15°C, provided optimal conditions for green roof establishment, while winter posed challenges due to frost. Both intensive and extensive green roofs have positive environmental, social and economic impacts, supporting the pillars of sustainable development. Examples of global green infrastructure further illustrate these benefits.

The impact of green roofs’ composition on its overall life cycle

Green roof systems have been developed to improve the environmental, economic, and social aspects of sustainability. Selecting the appropriate version of the green roof composition plays an important role in the life cycle assessment of a green roof. In this study, 10 compositions of an intensive green roof for moderate zone and 4 green roof compositions for different climatic conditions were designed and comprehensively assessed in terms of their environmental and economic impacts within the “Cradle-to-Cradle” system boundary. The assessment was carried out over a 50-year period for a moderate climate zone. The results showed that asphalt strips and concrete slab produced the highest total emissions. It was found that most greenhouse gases emissions were released in the operational energy consumption phase and in the production phase. The energy consumption phase (48.78%) for automatic irrigation and maintenance caused the highest Global Warming Potential (GWP) value (758.39 kg CO2e) in the worst variant, which also caused the highest life cycle cost (878.47€). On the contrary, in the best variant, planting more vegetation and lower maintenance and irrigation requirements led to a reduction in GWP (445.0 kg CO2e), but in terms of cost (506.6€) this composition didn't represent the best variant. The Global Warming Potential Biogenic (GWP-bio) compared to the Global Warming Potential Total (GWP-total) represents a proportion ranging from 0.8% to 78% depending on the proposed vegetation. Overall higher biogenic carbon values (up to 1525 kg CO2e) were observed for the proposed tall vegetation of Magnolia, Red Mulberry, Hawthorne, Cherry, and Crab-apple Tree. Based on the results of the multicriteria analysis, which included core environmental & economic parameters, biogenic carbon emission levels, the outcome of this paper proposed optimal green roof composition. Optimal intensive green roof composition was subjected to a sensitivity analysis to determine the impact of changing climatic conditions on CO2 emissions and life cycle costs. The results of the sensitivity analysis show that the optimal variant of the green roof can be implemented in the cold and subtropical zone with regard to CO2 emissions, but not with regard to life cycle costs.

«Green» structures in the urbanized environment: studying the impact of «green» roofs on environmental parameters and rainwater quality. Bibliographic review

A quantitative analysis of the most cited articles published in the Scopus scientometric database by 2023 is carried out. It is shown that most of the publications, the object of study of which are "green" structures, focus on the study of "green" roofs. It is shown that since 1981, the number of studies on green roofs has been steadily increasing: approximately 45% of articles focus on the benefits in terms of thermal impact and thermal insulation, 18% on rainwater drainage, 15% on air quality, 5% on the noise-absorbing properties of green roofs, and 17% on the costs of building and operating green roofs, recreational facilities, fire protection, and other related issues. The requirements and commonly used materials for a standard green roof are described, as well as the percentage of scientific publications, depending on the functions and layers of green roof construction involved. An analysis of the most cited scientific studies on the impact of green roof systems on wastewater quality was conducted. It is shown that the results of the studies presented in these publications indicate the need for further study of the impact of a "green" roof on the amount of pollution in the water flowing from its surface. It is emphasized that further research should focus on the structural layers of the roof (thickness and materials used), namely the thickness and types of substrate layers, as well as on the conditions of plant care (e.g., fertilization), especially on intensive green roofs. In addition, it should be studied and analyzed how the retention of rainwater by plants and the soil layer of a green roof affects the relative humidity of the air near the building during periods without rain. The most cited scientific studies on the reduction of air pollutants by means of green roofs are analyzed. It is concluded that future research should focus on the study of plant species that are well adapted to growing on roofs (in temperate climates) and most effectively carry out the process of photosynthesis, absorbing CO2 and releasing O2 into the atmosphere around the building. The article analyzes the most cited scientific publications on the noise-absorbing properties of green roofs. It is substantiated that it is necessary to maximize the percentage of green roofs implementation on all buildings and structures in the city so that green roofs can significantly affect the quality of the environment in urbanized areas.

Assessing the efficacy of green building design strategies in minimizing energy consumption in commercial buildings of Mumbai: A building performance analysis

This research paper investigates the effectiveness of green building design strategies in minimizing energy consumption in commercial buildings in the bustling metropolis of Mumbai, India. With a rapidly urbanizing and densely populated environment, Mumbai presents a unique setting for assessing green building practices. The research objectives focus on understanding the impact of various green building design features, such as green roofs, solar panels, and floor area optimization, on energy efficiency in commercial structures. The research employs a robust methodology, incorporating regression analysis to analyze data obtained from the Mumbai Municipal Corporation's building energy consumption records. Through this analysis, the study investigates the relationships between green building design parameters, building characteristics, and energy consumption patterns. Key findings indicate that specific green building features, including intensive and biodiverse green roofs and solar panel installations, significantly reduce energy consumption. Additionally, older buildings tend to exhibit lower energy consumption, emphasizing the need for retrofitting existing structures with energy-efficient solutions. The study also underscores the role of occupant density in influencing energy efficiency, with higher occupant rates leading to more efficient space utilization and energy use. The implications of this research are far-reaching, offering insights into tailoring green building strategies to the specific challenges posed by densely populated urban areas. These findings hold significance for sustainable urban development, policy formulation, architectural design, and the global effort to mitigate climate change.

Impact of outdoor heat adaptation on indoor thermal conditions – Combining microscale urban climate and building performance simulation

To what extent can outdoor heat adaptation measures in urban districts help to reduce high indoor temperatures in buildings and thus enhance indoor thermal conditions? To answer this question microscale meteorological simulation (MMS) and building performance simulation (BPS) are combined in a model chain approach. Two existing residential German districts with different urban designs are modelled in the MMS tool ENVI-met. For both districts, a representative residential building (one from the Wilhelminian period and one large panel construction type) is modelled using the BPS tool IDA-ICE. Different scenarios of heat adaptation measures are applied to analyse how changes in urban and building design (e.g. white (cool) roofs (high albedo), white traffic areas (high albedo), intensive green roofs, urban trees, facade insulation or facade greening) affect outdoor and indoor temperatures. The MMS results highlight that the district from the Wilhelminian period is less heat resilient and that the efficacy of heat adaptation measures on heat reduction in open space depends on the urban design and the daytime. Regarding the efficacy of heat adaptation measures on indoor thermal conditions, our findings indicate that the larger share of the indoor cooling effect is not caused by the outdoor air temperature reduction by the outdoor heat adaptation measures but by the change of the building physics in the BPS model (e.g. changing the surface reflectance of the white roofs). White roofs and intensive green roofs show the largest cooling effect by reducing the operative room temperature by more than 1 Kelvin. Our findings also demonstrate that facade insulation can act as both, climate adaptation and mitigation measures.

Water retention and runoff quality of a wildflower meadow green roof with different drainage layers

Extreme meteorological and hydrological phenomena, including high air temperatures and rainstorms, are becoming increasingly dangerous, causing floods and inundations, as well as long periods without precipitation, which lead to droughts. Green roofs may be one of the possible measures providing solutions to these problems. Rainfall, runoff and water quality data from three different intensive green roof models covered with wildflower meadows (WFs) over 20 months have been analysed to establish the extent to which the type of drainage layer affects hydrological performance. The field experiment was conducted at the Warsaw University of Life Sciences Water Centre park from November 2019 to November 2021. The monitoring of the quality and quantity of runoff was carried out on three models of green roofs incorporating wildflower meadows with drainage layers of 2 cm (WF 1) and 4 cm (WF 2) of polypropylene mat, as well as 6 cm of chalcedony (WF 3), in an urbanized area under moderate climate conditions. The model with the 4 cm polypropylene mat drainage layer retained approx. 6 % more rainwater compared to the model with the one made of chalcedony, and 4 % more than the one with the 2 cm polypropylene mat. Phosphates were detected in most of the leachates from all the wildflower-covered green roof models at 0 ÷ 0.459 mg PO4-P/L, 0 ÷ 0.402 mg PO4-P/L, and 0÷0.360 mg PO4-P/L for WF 1, WF 2 and WF 3. This may suggest that the type of drainage layer was not an important source of phosphates in the leachates.

Hygrothermal Performance of simple intensive Green Roofs with Different Irrigation Schemes

Urban mesoclimate is formed by a multitude of factors enhancing climate change characteristics like increasing temperature levels, reduced air moisture content, atmospheric pollution or extreme rain events. All of these factors could be attenuated by green roof structures. Unfortunately, this potential is not being tapped in current building practice. The majority of erected green roofs are built as extensive, i.e. non-irrigated, types. This results in a poor mesoclimatic impact as the water contents of these roof substrate layers are meagre, and vegetation layers are more or less inactive during the dry, hot summer months. Intensive green roofs, on the other hand, require higher load-bearing capacities and costs, both often not eligible for refurbishments. A promising approach is a combination of simple intensive green roof structures featuring a thin substrate layer with reduced irrigation techniques, especially under the usage of grey water. The hygrothermal performance of these structures in comparison between different irrigation schemes and solar radiation levels is shown in this article. Measurements were performed over a period of about two years. Hygrothermal performance shows the importance of an optimised relationship between irrigation scheme, substrate type and thickness in order to achieve a sufficient evapotranspiration and temperature balancing effect.

Perception of Green Roof Users with Their Mental Well-Being

Green roofs have grown popular in developing nations as an additional green space in a city when most of the land is being considered for new building construction but it has received less attention in Malaysia. Green roofs are also publicly accessible which provides a pleasant experience in recreational places that can relieve stress and soothe mind. Thus, this paper aims to determine the level of awareness of green roof adaptation among residents in high-rise residential buildings, as well as to investigate the relationship between intensive green roofs and mental health among residents in green residential buildings. It began by studying the literature on prior research, then collected data from a survey questionnaire on the target population. Statistical Package for Social Science (SPSS) version 27 will use to record and analyse the results of this study’s attempt to address the subject. According to the findings of the studies, the majority of residents are aware of the characteristics of an intensive green roof that influence their feelings. A minority of residents have mental health issues and they prefer five personal controls to keep their minds healthy based on their feelings. The essential conclusion is that a green roof may help in ensuring the preservation of a healthy mental state.

Investigating the cooling effect of a green roof in Melbourne

‘Green Our Rooftop’ aims to transform the rooftop of Treasury Place, a state government building in the inner city of Melbourne, into an intensive green roof under the notion of ‘Garden of Victorian Landscapes’. The concept behind the innovative green roof design is to break down perceived barriers to green roof retrofitting, limit the global temperature rise and help cool the city by advocating modifications in urban infrastructure (e.g. greening projects). This study quantified the cooling effect of the complex green rooftop of Treasury Place (which is characterised by a diverse range of plant types and topographies) by using ENVI-met to assess the air temperature and outdoor thermal comfort at rooftop and pedestrian levels. After verification through field measurements, the study also investigated how the adjustments in the green roof's design settings (e.g. leaf area index [LAI], plant height, soil moisture and additional green coverage) can further improve the green roof's thermal performance. The findings from our study indicate that the implemented green roof configuration effectively lowered the air temperatures at the roof level by 1.5 °C, simultaneously enhancing thermal comfort by 2.38 °C during hot summer days. This optimum performance was achieved when soil moisture levels were set at 0.6, plant height at 0.6, and LAI at 2.5. Our statistical analysis indicates that all these scenarios exhibited equivalent cooling benefits. Thus, a holistic approach optimizing LAI, plant height, soil moisture, and tree coverage combined is essential to maximise cooling impact when integrating green roofs into future developments in inner city areas.

Diagnosing the cause-effect relationship among deterrents to intensive green roof adoption: A hybrid EFDM-FDEMATEL approach

Green Roof (GR) has been recognized as environmentally friendly and practical approach to overcome environmental and societal challenges in urban contexts and contribute toward sustainable development. Nevertheless, various factors hinder GRs' broader adoption, which must be addressed to realize its social, environmental, and economic benefits. Prior studies have reported deterrents in diverse contexts, but not all are relevant to Tehran. The primary objectives of this study are to identify the factors that hinder the Intensive Green Roofs (IGRs) adoption in Tehran, and to analyze their relationship. To this end, a Systematic Literature Review is conducted to identify potential deterrents. Next, a fuzzy based Multi-Criteria Decision-Making approach is utilized to refine and analyze the interrelationships among the refined deterrents. Findings reveal seven novel barriers that have not been discussed in the existing literature and include exchange rate fluctuations, limited access to equipment due to sanctions, low energy tariffs, and low level of confidentiality (aristocracy of neighbors). In addition, the results indicate that the category of ‘cultural and climatic settings’ holds the most influential deterrents. The findings aid researchers and policymakers in devising effective strategies for widespread adoption of IGR in Tehran.

More insect species are supported by green roofs near public gardens

AbstractRapid urbanization is among the factors that decrease insect diversity. However, by offering suitable habitats, green roofs could lessen this adverse effect. Certain factors, like a nearby public garden, could be useful predictor variables to analyze to what extent green roofs can support insect communities. The study aimed to measure the insect diversity on intensive green roofs located near public gardens and on more isolated green roofs, within an urban setting. Insect species richness, abundance, and assemblages on the green roofs near public gardens differed from those on isolated green roofs. Results indicate that green roofs near public gardens will host more species, especially pollinators, consequently lessening urbanization’s negative effect. To properly understand how landscape factors impact insect communities on green roofs, future studies on green roofs’ biodiversity should consider public gardens and their influence on urban biodiversity.Implications for insect conservationThe planning and establishment of a green roof near public gardens would probably enhance biodiversity conservation in an urban setting.

Carbon dioxide reduction from an intensive green roof through carbon flux observations and energy consumption simulations

Green roofs have the potential to reduce carbon dioxide directly through photosynthesis and indirectly through building energy savings. Most previous studies either focused exclusively on the direct or indirect CO2 reduction of GRs, resulting in an incomplete assessment. A comprehensive assessment of the CO2 reduction potential of GRs would aid in promoting their use as carbon credits in the carbon trading market. This study quantifies the total CO2 reductions from a newly built intensive green roof with yearlong carbon flux observations and building energy simulations. Our results indicate that direct and indirect carbon reductions from IGR significantly differ, with the monthly direct and indirect CO2 reduction ratio ranging from 1:5 to 1:130. Direct and indirect CO2 reduction exhibits significant seasonal trends, with peak direct reduction in autumn and peak indirect reduction in summer. Overall, the total annual CO2 reduction from this IGR system is 4355.6 g CO2·m−2, of which 46.6 g CO2·m−2 and 4309 g CO2·m−2 were direct and indirect, respectively. Further research should evaluate the long-term integrated carbon reduction over the life cycle of the GRs. The findings of this study could provide evidence to leverage GRs as a nature-based solution to achieve net-zero carbon emissions.

Green strategies for improving urban microclimate and air quality: A case study of an Italian industrial district and facility

Densely built areas are affected by higher air-pollutant concentrations, representing a significant risk to public health. At the same time, urban settlements have a remarkable environmental impact: cities are responsible for 70% of annual carbon emissions while buildings account for 37% of global energy and process emissions. Moreover, people living in urban areas are frequently exposed to extreme micro-climate conditions caused by the urban heat island effect, related to increased external air temperature and peculiarities of the built environment. Given this framework and considering the Sustainable Development Goals, it is necessary to point out some effective and strategical mitigation measures to ameliorate micro-climate conditions, reduce pollutants concentration and enhance building performance. This paper investigates the potential advantages of green roofs as retrofitting solutions and tree planting on several micro-climate parameters and particulate matter concentration, considering an industrial district located in Italy and using ENVI-met software. The influence of the extensive green roof on energy performance is further investigated at the building level recurring to Design Builder energy models. Results showed that an extensive green roof could reduce external air temperature by up to 1.5 °C, outer surface temperature by up to 15 °C and wind speed by 50% at roof level compared to current state conditions. The application of the green roof let also to achieve energy savings of 15% for both the summer and winter seasons. Focusing on the effect on particulate matter, intensive green roof solutions proved to be more efficient in capturing air pollutants.

Green roof cooling and carbon mitigation benefits in a subtropical city

Green roofs are promoted as an effective nature-based urban heat island mitigation strategy. Green roof cooling and energy-saving benefits have been simulated for various climatic zones, but mainly at the building scale. Due to a lack of fact-based information on neighborhood cooling benefits, green roof construction lags and has rarely been incorporated into urban planning actions. This study investigated the thermal benefits and energy savings of green roofs for the central area of the Xianlin Campus of Nanjing University at the neighborhood scale. Three scenarios were simulated for a hot summer day using a validated ENVI-met model: a base case (S0), extensive green roofs (EGRs) (S1), and intensive green roofs (IGRs) (S2). The air temperature cooling benefit from green roofs extended downwards to the pedestrian level. The EGR scenario achieved a maximum 0.29 °C air temperature reduction at the pedestrian level and 0.37 °C at the rooftop level. The IGR scenario achieved a maximum 0.35 °C air temperature reduction at the pedestrian level and 0.45 °C at the rooftop level. EGRs and IGRs reduced energy demands for air-conditioning by 0.39 kWh·m−2·d−1 and 0.56 kWh·m−2·d−1 and CO2 emissions by 31,997 kg·d−1 and 45,967 kg·d−1, respectively. These results confirm that green roofs yield substantial cooling and carbon mitigation benefits. Our study provides essential data to establish green roofs as mainstream cooling technology in subtropical cities. The results also imply that urban planners and policymakers may need to embrace the implementation of green roofs in long-term planning and building design practices to improve urban thermal environments, reduce building energy demand, and curb carbon emissions.

Potential and Benefit of Green Roof Energy Renovation of Existing Residential Buildings with a Flat Roof in Belgrade

Green roofs are considered to be one of the optimal tools for saving energy and protecting the environment in developed countries. In this paper, an analysis of the possible application of green roofs on existing residential buildings with flat roofs is presented. In the economic analysis, models of existing buildings in Belgrade, with two different types of green roofs, are studied. A key indicator of investment profitability in this investigation is the net present value (NPV) of the green roof project. Besides the private economic impact, other aspects of green roof applications, significant for sustainable development, have been highlighted. The values of the reductions in the annual energy needed for heating and cooling are compared for different scenarios. A maximum energy saving of 22% in the heating season is determined in the building energy simulation program for the model with an intensive green roof. Life cycle profit analysis was based on the probabilistic approach. The corresponding variance-based sensitivity analysis determined the impact of various parameters on the final result. In all models, the first order sensitivity index, which measures the impact of the number of residential units on the NPV, ranges from 12.2% to 63.6%. Sensitivity analysis showed that the benefit of property value increase has the highest influence on the calculated NPV in scenarios that account for this benefit. The obtained results in those scenarios indicate that the most probable NPV at the end of the life cycle is EUR 43/m2 and EUR 82/m2 for extensive and intensive green roofs, respectively.

On the identification of most appropriate green roof types for urbanized cities using multi-tier decision analysis: A case study of Istanbul, Turkey

Green roofs (GRs) have gained considerable attention in recent years as a sustainable solution for densely urbanized cities to mitigate the negative impacts of urbanization on the environment. Hence, this research proposed a hybrid multi-criteria decision-making scheme aiming to determine the best-matched GR formation for metropolitan city of Istanbul. Therefore, fuzzy AHP and TOPSIS were adopted for weighting a total of 16 criteria and performing binary prioritization of intensive GRs (IGRs) and extensive GRs (EGRs) for the focalized region, respectively. Two GR types were examined based on four major dimensions, i.e., financial, technical, knowledge, and environmental aspects. The results highlighted the vitality of financial (35.01%) and environmental (34.91%) facets, followed by the technical (21.83%) dimension, whereas knowledge (8.24%) was the least significant aspect. Also, initial and operational costs (global weight: 17.37%) and stormwater retention capacity (global weight: 16.98%) outperformed their counterparts. Combining the criteria weight computed and the average scores of each factor with regard to the city further illustrated that EGR (CCi: 0.7442) was found as the optimal GR configuration for Istanbul. The key findings of this research aimed to contribute to the growing GR literature by exploring the paradigms regarding the sustainability and resilience of urbanized cities.

Comparison on the stormwater runoff effects of roof greening in different urban functional areas

Global climate change and the expansion of impervious surface in urban areas have increased the risk of urban flood. As a measure with low impact development (LID), roof greening can effectively reduce stormwater runoff, serving as the first barrier to prevent rainwater from entering the urban drainage system. We used the CITYgreen model to simulate and analyze the impacts of roof greening on hydrological parameters (e.g., surface runoff) in the new and old residential areas and the commercial areas in Nanjing City, and further investigated the variations in stormwater runoff effects (SRE) among these functional areas. We compared the SRE between different green roof types, and between green roofs and ground-level green spaces. The results showed that the proportion of permeable surface would increase by 28.9%, 12.5% and 49.2% respectively in the old residential area, new residential area and commercial area if all building roofs were greened. In a rainfall event with a return period of two years and a duration of 24 hours (precipitation=72 mm), the implementation of roof greening in all buildings in the three sampling areas could reduce surface runoff by 0-19.8% and reduce peak flow by 0-26.5%. The reductions in runoff by green roofs could be translated to a rainwater storage capacity of 223-2299 m3. The commercial area had the highest SRE by installing green roofs, followed by the old residential area, while the new residential area had the lowest SRE. The rainwater storage volume by per unit area of extensive green roof was about 78.6%-91.7% that of the intensive green roof. The storage capacity by per unit area of green roof was 31%-43% of that in the ground-level greenery. The results would provide scientific references for the site selection, sustainable design and incentive development of roof greening from the perspective of stormwater management.

Energy consumption for space cooling and heating depending on flat roof structures renovation. Case study of the Healthcare center Nis

Since the reduction of energy consumption and efficient energy use, particularly in the building stock, is the priority for contemporary societies, the ways of how to improve the existing buildings should be examined. Flat roofs, as a part of the existing building thermal envelope, are recognized as a field of intervention for improving efficient energy use for space cooling and heating. The topic of the paper is to determine to what extent different improved roof structures affect energy consumption intended to achieve thermal comfort. Comparative analysis of four roof structures was conducted for the building of Healthcare center Nis in Serbia, one improved non-walkable flat roof structure and three green roof systems. Urbancsape extensive green roof system was used in all tested green roof models: non-walkable extensive green roof, walkable extensive green roof, and extensive and intensive green roof systems within walkable terraces. DesignBuilder software was used for energy modeling. The obtained results indicate a slight decrease in energy consumption for building models with green roofs compared to the building model with the improved non-walkable roof structure, along the cooling period, by approximately 1,5%, which is correlated with previous studies in similar conditions. On the other hand, the reduction of energy consumption over the heating period was negligible (less than 1%). Considering the results and predominant usage of commercial Urbanscape extensive green roof system in all green roof models, being characterized by small thickness (10.64 cm) and light structure, and which is predicted to be installed over the already well-insulated roof, the system?s role as an additional thermal mass was confirmed.

Capturing Carbon Dioxide from Human-Driven Vehicles by Green Structures for Carbon Neutrality

For carbon neutrality of cities, we should compensate carbon dioxide gains from vehicles. Human-driven ones are not carbon-free because cyclists perform hard work. Green roofs are an adequate carbon-capturing facility, especially for the dense building. We used the previous author’s data for carbon dioxide sequestration of them. The carbon dioxide gained from a cyclist is calculated using aggregated indicators for hard work and rest. Also, the experimental data for a cyclist on an exercise bike is used as an alternative. For recumbent bicycles, drag is 0.2÷0.3 of drag for classical ones. This allows estimation of the carbon dioxide gain for this promising technology. The results show that road bicycles require only 4.4 m2 of extensive and 1.37 m2 of intensive green roofs per cyclist. Recumbent bicycles need two-time fewer areas. Electric public conveyances and cars require one-two order of magnitude more area.

Investigation of spatial variability of soil hydraulic properties for application in intensive green roofs

Investigation of spatial variability of soil hydraulic properties for application in intensive green roofs