Assessing Ecological and Economic Sustainability of Green Roof Systems in Semi-Arid Urban Landscapes

Abstract

With an emphasis on the thermal performance (TP) and energy efficiency (EE) of green roof (GR) systems, this study explores these systems' ecological and economic sustainability in urban settings. A simplified methodology was created to assess the TP of both extensive and intensive green roof variations. The findings underscore the critical function of GRs in reducing heat flux in buildings with insufficient insulation, stressing that larger roof substrates result in more significant heat reduction. Drier soil conditions provide better thermal insulation. Other important elements included soil moisture content and its effect on evapotranspiration. Specifically, the broad and intense green roof systems improved energy and environmental performance and dramatically lowered temperatures by roughly 3.3 and 3.5 degrees Celsius, respectively. The temperature drops affect roofs' outside surface temperature and contribute to alleviating the urban heat island (UHI) effect. Intensive green roofs IGRs, in particular, showed better thermal performance because of their higher Leaf Area Index (LAI) and thicker substrate. A multi-criteria analysis comparison was carried out to evaluate different GR systems' energy and environmental performance. The findings ascertain that the technique of IGR is a feasible option for lowering the building cooling energy requirements and lessening the effects of UHI, especially in semi-arid climates. This study offers helpful information for architects, legislators, and urban planners on how to use GR systems to improve ecological sustainability and economic benefits in urban settings.

Introduction

Many countries in the world have turned to urbanization due to rapid population growth and economic progress, and urban development is an indicator of the health of the local economy, especially when land use shifts from private to business to rustic regions on the edges of urban communities (Mihalakakou, Souliotis, et al., 2023; Prall, Olazabal, et al., 2023). In addition, urban development faces many challenges, including the lack of farms and forests, poor air and water quality, the social and economic consequences of economic imbalance, social dispersion, and foundation costs. Thus, urbanization directly affects land use modification (Aini, Wikantiyoso, et al., 2025; Mihalakakou, Souliotis, et al., 2023; Prall, Olazabal, et al., 2023). Furthermore, urban communities are hotter than their surrounding rural areas because of the way energy and water are exchanged between the land and the environment. This results from more extensive asphalting in urban communities, and thus urban residents are more powerless to the hurtful impacts of a more widespread warming climate (Abdulrazzaq, 2025; Malamis, Katsou, et al., 2016; Pumo, Alongi, et al., 2023).

By 2050, 9.2 billion people will own land, and almost every one of them will live in urban communities in emerging countries, according to UN measures. Thus, the rapid urbanization of the planet has modified radiant, warm, humid, and streamlined surface properties as well as the urban climate (Kim and Brown, 2021; Qian, Meng, et al., 2023; Yousaf Raza, Hasan, et al., 2023; S. Zheng, Chen, et al., 2023). In addition, the expression for distinction in temperature is the Urban Heat Island (UHI) (Wikantiyoso and Tutuko, 2013), a deep-rooted human-caused environmental change (S. Zheng, Chen, et al., 2023). The Iraqi capital, Baghdad, has seen its population increase every decade at a rate higher than 45% over the past 60 years. The comparative development of urban foundations has led to a dramatic expansion of anthropogenic heat emissions and asset dependence (Kim and Brown, 2021; Qian, Meng, et al., 2023; Yousaf Raza, Hasan, et al., 2023; S. Zheng, Chen, et al., 2023).

Throughout the course of recent years, GR (green roof) frameworks have developed from hurriedly made, case-explicit plans to painstakingly arranged roofing frameworks that integrate developing media, a waste layer, channel material, and other particular plants with elements of an upset roof. GR frameworks have been effectively utilized in a couple of explicit conventional development applications for millennia, tracing all the way back to old Mesopotamia (Hussien, Jannat, et al., 2023; Talwar, Verma, et al., 2023). The idea of a "green roof" is not new; its fundamental components have been used by people for a long time. In later times, expanding urbanization and the infringement of "urban spread" onto green belt regions have come about in a "turning gray" climate and a decreased open space. Developing urban thickness to forestall urban spread, environmental mindfulness, and the resulting loss of geographic personality have all added to the expanded understanding of the upsides of GRs. Among the types of GRs are intensive and extensive roofs (Abdulrazzaq, Ahmed, et al., 2020; Wei, Xiong, et al., 2023; Zuberbier, Stevanovic, et al., 2024). These roofs are useful for herbs and plants that are tolerant in the dry season, such as beautiful flowers. They are developed with a substrate depth of less than 15 cm, cost less than an extensive green roof (EGR), and are lighter in weight. While intensive green roofs (IGR) need a substrate depth of more than 15 cm and can uphold a more prominent scope of vegetation, including small trees and hedges (Fei, Fu, et al., 2023; Kazemi, Rahif, et al., 2023; Mihalakakou, Souliotis et al., 2023).

In addition, IGRs require comparative support to ground-level finishing since they are intended to be public spaces. GR frames designed to mitigate the effects of the UHI effect are demonstrated. GRs improve the amount of evapotranspiring plants in the constructed climate, capture airborne particles, absorb gaseous pollutants such as carbon dioxide (CO₂), and diminish the amount of surfaces accessible for sun-powered energy reradiating. Together, these cycles make an air that is, in many cases, cooler and less affected by contamination (Jumaah, Abdulrazzaq, et al., 2021; Liu, Kong, et al., 2021; Tan, Kong, et al., 2023; X. Zheng, Kong, et al., 2023). GRs assist with bringing down inside building temperatures in warm environments by lessening the warm changes that the roofing framework imparts much of the time, resulting from cyclical heating and cooling. This is because they safeguard building rooftops from direct sunlight (Borghei, Niroumand, et al., 2025; Jamei, Chau, et al., 2023; Salvalai, Marrone, et al., 2023; Seyedabadi, Eicker, et al., 2021). Studies have shown that all through the colder time of year, GRs give discernibly more protection. Due to the rising impacts of an unnatural weather change, it is currently desirable to consider how GRs could keep cool in the mid-year (Jamei, Chau, et al., 2023; X. Zheng, Kong, et al., 2023). Rooftop gardens can significantly further develop urban air quality and carry it nearer to normally vegetated places in light of the plant's ability to retain CO₂ and other greenhouse gases (GHG) from the surrounding air. A 1-square-meter fixture of grass-covered roof assured the potential elimination of 0.2 kg of airborne poisons yearly and provide people 70% of the expected oxygen (Mahmoudi, Mousavi, et al., 2021; Viecco, Jorquera, et al., 2021).

The main objective of this study is to evaluate the environmental and economic sustainability of GR systems and apprise them of the potential benefits and viewpoints of GR systems in subtropical climates. Specifically, this study will examine the TP of common EGR and IGR systems under varying climatic conditions.

1. 2.   MATERIAL AND METHODS
   1.    Climate of the study area

Baghdad city is located at latitude 33.312805°N and longitude 44.361488°E, it covers an area of 20.42 hectares, the city's climate is semi-arid, subtropical, and hot in the summer. The research region receives 723.24 mm of rainfall on average annually, with 59.9% of the total falling during the Northeast monsoon. The average temperature peaks at around 41.5°C between April and May, while it drops to its lowest, approximately 21.4°C, during December and January. During the day, the relative humidity ranges from 41% to 81%.

Functional Element of Green Roofs

One of the vital advantages of GRs is the administration of stormwater through better water maintenance, which diminishes the volume of water released to storm sewers. Precipitation is either accumulated by plants and afterward vanishes in the developing substrate of the GR, or it is gathered and put away in reservoirs, downpour barrels, or on-location capacity tanks. Stormwater maintenance on location can decrease consolidated sewer spills that defile surface water quality and may try and eliminate land-based stormwater lakes (Buckley, Connolly, et al., 2023). All the more significantly, GRs can likewise work on the nature of stormwater by lessening runoff temperatures and separating the water through soil media. A subsequent report in Portland, Oregon, found that the utilization of GRs to divert runoff has been fruitful in protecting and resuscitating the nearby Coho, Chinook, and steelhead salmonid populaces in the Willamette Stream (Abdulrazzaq, Al-Abdaly, et al., 2024; Li and Liu, 2023; Pumo, Francipane, et al., 2023; Wooster, Fleck, et al., 2022). An extra benefit of having a GR is energy preservation. Studies have shown that all through the colder time of year, GRs give discernibly more protection. Be that as it may, given the rising impacts of an unnatural weather change, it is currently desirable to consider how GRs could keep cool in the mid-year (Jamei, Chau, et al., 2023; X. Zheng, Kong, et al., 2023). The possibility that urban communities and metropolitan regions experience higher temperatures than provincial and suburban regions is known as the "heat island impact" in urban settings. This 2 to 5 °C temperature contrast is particularly observable in the late spring and may add to recognizably higher contamination levels (Dwivedi and Mohan, 2018). This is essential because of the hard rooftops of metropolitan regions, which can trap heat and mirror light. Therefore, cooling structures with level roofs are connected to an outstanding ascent in energy use. By covering the rooftop with vegetation, GRs assist with diminishing temperatures, as per studies intended to recreate the impacts of a heat island (Jamei, Chau, et al., 2023; Taguchi and Kikuchi, 2015; X. Zheng, Kong, et al., 2023).

Components of GRs

A layered roofing framework is usually utilized in GR plans, which are planned to support vegetation growth and retain water for plant take-up while also minimizing surface water accumulation and reducing the risk of ponding. The roofs are made so that water channels through the media in an upward direction, then, at that point, evenly down a layer of waterproofing, and lastly, out the power source. A typical GR consists of several key layers, including: (1) vegetation, (2) growing medium or substrate, (3) channel texture, (4) seepage layer, (5) root obstruction, (6) waterproofing membrane, and (7) the roof deck. Figure 1 presents a schematic illustration of the GR system.

Figure 1. Schematic representation of green roof layers

1.    Steel support: To help the heaviness of the different layers of a GR framework, for example, the developing media, root hindrance, waste layer, channel layer, roof deck, and watertight film, steel upholds an estimated 1m × 1m × 0.5m, see Figure 2.

Figure 2. Provision of concrete roof deck with steel support

1. b.   Roof deck: Serving as the structural base of the GR system, the roof deck is engineered to have satisfactory underlying respectability and capacity to securely endure all heaps, burdens, and impacts that might be sensibly expected. Five precast, built-up substantial chunks with aspects of 1m × 1m × 0.05m each were created as the roof deck (1:1.5 :3). One precast, built-up substantial piece was picked as the reference roof out of the five aggregates. Figure 3, individually, accommodates the arrangement of a substantial roof deck with steel support and the covering of said roof deck with PVC sheet.

Figure 3. Provision of coverage of concrete roof deck with PVC sheet

1. c.   Water proofing layer: Positioned directly above the roof deck, the waterproofing layer functions as a protective barrier to protect from water harm through the deck layer. Its specific estimations were 1m × 1m × 0.005m; the waterproofing layer is totally waterproof and is intended to endure longer than some other parts of the green roof framework.
2. d.   Root barrier: One more layer of a green roof framework is known as a root boundary. Contingent upon the framework, it is set over the waterproofing layer and effectively holds roots back from infiltrating the waterproofing film. The layer is estimated to be 1m × 1m × 0.003m.
3. e.   Drainage layer: The thermo physical properties of GR consisting of several layers: a waterproofing layer, a root barrier, a drainage layer, and a filter layer. The thermo physical properties of the GR are shown in Table 1.

Table 1. Thermo physical properties of green roof layers

Layer	Thermal conductivity l (w/m K)	Density r(Kg/m3)	Specific heat Cp (J/Kg K)
Waterproofing layer	0.17	120.00	920.00
Root barrier	0.03	90.00	990.00
Drainage layer	0.08	500.00	920.00
Filter layer	0.06	160.00	2500.00

1. f.   Growing medium or substrate: Vermi compost was utilized in a 1:1 ratio to generate two different kinds of growth media or substrates. Over the few layers of the channel layer, seepage layer, root obstruction, waterproofing layer and precast supported substantial chunk, with an area of one square meter, there were “soil” (sandy mud topsoil) and “soilless” (coco peat) substrates. In light of the powerful root profundity of the tomato and marigold crops, the substrate profundities of endless soilless substrate were estimated; these profundities were 30 cm and 15 cm, separately. In green roof systems, the wood cover was used to support the substrate. Table 2 lists the physical characteristics of both soilless and soil substrate.

Table 2. Physical properties of substrate

Properties	Soilless substrate	Soil substrate
Bulk density (g/cc)	0.12	1.40
Particle density (g/cc)	1.20	2.40
Porosity (percent)	90.00	42.00
Water holding capacity (percent)	70.00	30.00

1. g.   Vegetation: To assess the warmth exhibited by GR frameworks, vegetable and blossom crops were analyzed. The yields were established simultaneously in a 1 m² segment of the GR utilizing both soil-based and soilless growing media. The foliage coverage of marigold and tomato plants on the HGR with soil substrate and without soil is displayed separately in Figures 4 and 5. Subtleties of the extraordinary and broad GR tests, as well as the harvest trial, are given in Table 3.

Figure 4. Foliage cover of tomato crop in intensive green roof with soil substrate

Figure 5. Foliage cover of marigold crop in extensive green roof with soil substrate

Table 3. Crop experiment details

Component	Details
Crop	Tomato	Marigold
Variety	Co.3	MDU.1
Spacing	30cm×30cm	30cm×45cm
Duration	110 days	120 days
No. of Plants	12	9

Energy Balance of Green Roof

The Fast All Season Soil Strength (FASST) model served as the foundation for the energy balance model used in the current investigation of the GR experiment. A single layer of plants on a growth medium is the paradigm for the GR. The vegetation layer is modeled as a steady-state, semi-infinite planar surface that influences the intensity trade between the substrate layer and the encompassing air. It is characterized by emissivity, albedo, level, and leaf or plant partial inclusion. A homogenous layer that permits both reasonable and inert intensity streams is the model for the substrate layer. Emphasis was placed on the most important characteristics of the GR model, which are the exchange of two types of radiation, longwave and shortwave, inside the foliage or vegetative layer, heat conduction and storage in the substrate layer, evaporation, and the impact of vegetation on convective heat transmission. Two energy balance conditions including substrate temperature (qg) and foliage temperature (qf) are all the while settled at the substrate (Fg) and foliage (Ff) levels to decide the intensity course through a GR. Figure 6 shows the terms of the situations for energy balance.

Figure 6. Energy balance for a green roof

Environmental Benefit

Several measurements were performed to determine how beneficial a GR system is to the environment. The thermal resistance (R-value), conduction transfer coefficient (U-value) μ(w/(m²K)), and heat flux (W/m²) were measured by several equations as described in previous Studies (Mahmoodzadeh, Mukhopadhyaya, et al., 2020; Tighnavard Balasbaneh, Sher, et al., 2024; Wong and Jim, 2015).

•    Thermal resistance (R-value)

R-value is a measure of thermal resistance metric used in roofing design. It represents the layer thickness ratio to substrate thermal conductivity per unit area per unit time under uniform conditions.

$ThermalresisanceR=\frac{Thicknessoflayers\left(m\right)}{Thermalconductivity\left(\frac{W}{mK}\right)\times Surfacearea\left(m^2\right)}$ (1)

•    Conduction transfer coefficient (U- value)

The conduction transfer coefficient, or U-value, is the inverse of R-value; it shows how well a roof conducts heat or the pace of intensity moving (in watts) through one square meter of roof structure.

$Conductiontransfercoefficient\mu \left(\frac{w}{m^{2}K}\right)=\frac{1}{Thermalresisance\left(R\right)}$ (2)

•    Heat flux through roof

Heat flux or thermal flux is the rate of heat transfer through a given roof, per unit area and unit time.

$Heatflux\left(\frac{W}{m^2}\right)=\mu \times \Delta T\left(temperaturedifferencebetweenlayers\right)$ (3)

The temperature was measured using a digital temperature meter, and a solar cell-based pyranometer was used to measure solar radiation at the foliage canopy and ground level of the substrate with a resolution of 1 w/m². A digital infrared radiative meter was used to determine infrared radiation, and a digital heat flux meter was used to measure the latent heat (L) of vaporization, in addition to measuring wind speed. An anemometer was used, and this speed was measured at a height of two meters above the roof slab.

1.    Statistics
   1.    Mann-Kendall test (MK test)

To investigate hydrologic information, the non-parametric (Mann-Kendall test) may be utilized to recognize monotonic designs, yet not directly 100% of the time. It is primarily used to identify trends in time series data. It is helpful for environmental data, climate studies, and other disciplines where data often deviates from a normal distribution. This test is appropriate for the nature of the study data. While it is powerful and frequently applied, it does have certain limitations—particularly when dealing with autocorrelated data or short time series, where trend detection may be less reliable. Despite these constraints, the Mann-Kendall test was selected for this study due to its effectiveness with non-normally distributed datasets, resilience to missing values, and its established use in similar environmental trend analyses. According to Donald, Jean, et al. (2011), the Mann-Kendall test has been used mainly on critical patterns where uncertainty in predictability is unnecessary.

The formula in Equation 4 is utilized to compute the MK test statistic, S.

$S={\sum }_{i=1}^{N-1}{\sum }_{j=i+1}^{N}sgn(x_j-x_i)$ (4)

Here, $x_j$ and $x_i$ represent the annual values for years j and i, j>i respectively, and N denotes the total number of data points. The function $sgn(x_j-x_i)$ is evaluated as follows:

$sgn(x_j-x_i)=\{\begin{array}{c}\hfill 1if(x_j-x_i)>0\hfill \\ \hfill 0if(x_j-x_i)=0\hfill \\ \hfill -1if(x_j-x_i)<0\hfill \end{array}$ (5)

This measurement addresses the quantity of positive contrasts, short the quantity of negative contrasts for every one of the distinctions considered. For enormous examples (N>10), the test is conducted utilizing an ordinary estimate (Z measurements) with the mean and variance calculated as follows:

$Var\left(S\right)=\frac{1}{18}[N(N-1)(2N+5)-{\sum }_{p=1}^q{t}_p(t_p-1)(2t_p+5)]$ (6)

The parameter q represents: the number of tied groups, where there is no differentiation between analyzed values, while tp denotes the number of data values within the pth group. The sample statistic Z is calculated using the advantages of S and VAR (S) along with other relevant factors.

$Z=\{\begin{array}{c}\hfill \frac{S-1}{\sqrt{}Var\left(S\right)}ifS>0\hfill \\ \hfill 0ifS=0\hfill \\ \hfill \frac{S+1}{\sqrt{}Var\left(S\right)}ifS<0\hfill \end{array}$ (7)

When a trend's Z value is positive, it indicates an ascending trend; when it is negative, it indicates a descending trend. This method is used to assess if a trend is statistically significant. The statistic Z has a normal distribution. Z₁-α/2, obtained from conventional normal cumulative distribution tables must be larger than Z₀ to determine the presence of a significant level at the α by conducting a two-tailed test to ascertain a monotonically growing or decreasing trend. Z is greater than Z₁, in which case H₀ is denied. The Z values were examined when the significance level of 0.05 was reached.

1. 2.   Sen’s slope estimator

Sen’s non-parametric estimator was employed to calculate the magnitude of trends in both seasonal and annual time series data (Sen, 1968). This method is applicable when the trend is assumed to be linear, as in the following conditions:

$Q_i=\frac{x_j-x_k}{j-k}$ (8)

Sen's gauge of slant is a strategy for evaluating patterns in time series information. It works out the incline between sets of pieces of information (xj and xk) where j>k. A period series with n esteems yields N= n(n-1)/2 slant assessments. To find the median, all N Q_i values are positioned from littlest to biggest. This strategy gives a steady gauge of the information's pattern by considering different pairwise slants, making it helpful for pattern examination in time series information.

$Q=Q_{\left[\frac{(N+1)}{2}\right]}$ , if N is odd (9)

$Q=\frac{1}{2}(Q_{\frac{N}{2}}+Q_{\left[\frac{(N+2)}{2}\right]})$ , if N is even (10)

The assessment of parameter B in condition f(t) was done by computing the distinctions between the noticed qualities x_i and the comparing gauges Qt_i. To get a gauge of B, the median of these distinctions, registered as n values, was used. The cycle was smoothed out through the Succeed layout program Makesens, which calculated significant measurements like the MK measurement S, Sen's incline Q, and the capture B for the analysts.

1. 3.   RESULTS AND DISCUSSION
   1.    Temperature trend of Baghdad

Seasonal and yearly temperature trends were examined for the mean maximum temperatures (TXM) and mean minimum temperatures (TNM) across three stations, including Baghdad. The trend analysis was conducted in three distinct steps. The annual and seasonal precipitation time series are examined in three periods: First, the non-parametric MK test was applied to determine whether there was a monotonically increasing or decreasing trend; second, Sen's non-parametric slope estimator was used to estimate the magnitude or slope of the linear trend; and third, regression models were created.

Significance of Trend Analysis

Significance trend analysis was analyzed by the MK test, which MS Excel predicted; the result of the Mann-Kendal analysis to deduct the trend is given in Table 4.

Table 4. Summary of the MK analysis

Annual and Season	Man-Kendall analysis
	Baghdad	Sulur	Kinattukkadavu
Mean maximum temperature
Winter	0.92	1.54	0.47
Summer	1.67 +	2.58	3.13
Monsoon	0.91	3.97	2.94
Post monsoon	1.61	2.69	2.16
Annual	4.67	3.03	2.94
Mean minimum temperature
Winter	0.37	0.79	2.77
Summer	2.16*	3.94	3.88
Monsoon	0.66	0.45	3.97
Post monsoon	1.15 +	2.6	2.81
Annual	3.6	2.16	4.23

The results obtained for the temperature trend in Baghdad, Sulur, and Kinattukkadavu for the MK analysis of TXM and TNM in different seasons are shown in Table 4. Where the values of the Kendall tau correlation coefficient (τ) indicate the strength and direction of these trends, a positive τ value indicates an upward trend, while a negative value indicates a downward trend and τ values close to zero indicate no significant trend. For Baghdad, the results show through positive τ values that there is an increasing trend in TXM during the summer, monsoon, and post-monsoon. Similarly, Sulur witnessed an increasing trend in TXM during the summer and post-monsoon seasons. At both locations, the TNM in summer shows a notable significant upward trend. While Kinattukkadavu experiences a more pronounced warming trend, the TXM show a positive τ value throughout all seasons. In addition, the TXM values in Kinnatukadavu indicated a strong increasing trend, especially during the summer season. When looking at annual trends, the results showed that the three regions studied showed an upward trend in TXM, with The Kinatukadavu district showing the largest increase. Regarding annual TNM trends, the results for Sulur and Kinattukkadavu show an increasing pattern, with Kinatukdavu experiencing the most pronounced warming. In this study, Baghdad showed an upward trend in average maximum temperatures. This may be a result of population expansion, buildings that lack thermal insulation, and concrete blocks that cover many areas at the expense of green spaces (Anas and Yahya, 2023).

Structural Capacity of Green Roof Systems

The structural capacity of several types of GR systems was examined, including extensive and intensive systems. The structural load capacity was sufficient to maintain the soil, plants, and other layers. The structural capacity of all elements was determined by multiplying the element's density by its depth. The structural capacities of treatments T₁ and T₂ were examined as shown in Table 5. The results indicated that the loads on the concrete slab, filtration layer, root barrier, drainage layer, and waterproofing layer were the same as on the entire section. The results also showed that GR system treatments have structural capacities for substrate load and vegetative load that vary according to the soil layer depth and the type of vegetation cover used. This is because the GR system and its classifications are directly influenced by the type of vegetation cover and the depth of the growing medium (soil layer) (Anas and Yahya, 2023; Harris, 2014).

Table 5 shows the analysis results of the structural capacities associated with various GR system types, specifically intensive and extensive GRs. In addition to presenting the various structural load components that these systems must support, the results showed that these components of the structural load contribute to the total load borne by the GR system. The findings indicated that the total load of the IGR system was 65.61 kg.f/m², and the factorial load reached 78.73 kg.f/m², which is a more comprehensive assessment of the bearing capacity. This indicates that the structural elements of the IGR system must be able to support this load without encountering structural problems. While the results indicated that the EGR system has a total load of 97.61 kg.f/m², and a factorial load of 117.13 kg.f/m², which are higher compared to the loads of the IGR system. This indicates that the EGR system must be designed to handle a greater load, which includes factors such as vegetation and soil, without compromising its structural integrity. These results confirm that the EGR system is better than the IGR system. This is explained by the fact that the IGR system has a complex structure and requires measures and care to maintain it, in addition to the expense of such maintenance (Lee and Jim, 2020; Perivoliotis, Arvanitis, et al., 2023).

Table 5. The structural capacity of the green roof systems

Structural load capacity (kg.f/m2)	Intensive green roof system	Extensive green roof system
	T1	T2
Concrete slab load	47.50	47.50
Vegetation load	9.76	9.76
Soil load	3.00	35.00
Filter layer load	0.48	0.48
Drainage layer load	4.00	4.00
Root barrier load	0.27	0.27
Waterproofing layer	0.60	0.60
Total load	65.61	97.61
Factorial load	78.73	117.13

Rate of Heat Flux at Substrate

Sensible heat flux (H) (convection), latent heat flux (LE) (evaporation), long-wave thermal radiation exchange between leaf surfaces and the atmosphere, and conductive heat flux within the substrate collectively contribute to balancing incoming solar radiation within the GR system. Figure 7 shows the heat flux rate of a soilless substrate under IGR. The heat flux rate of each component in the substrate energy balance equation for the IGR (T₁) and the EGR (T₂) are shown in Figure 7, respectively. Figure 7 shows that all energy balance components in both treatments progressively decrease from the initial stage to the harvest stage. This may be due to there being less plant covering to allow water molecules to drain from the substrate (Chen, 2022; He, Yu, et al., 2017), as the EGR and IGR systems exhibited the lowest heat flux during the initial and flowering stages and the highest heat flux during fruiting as shown in Figure 7. This may be due to the depth of the substrate being one of the most important factors that affects the amount of heat absorbed by the GR, in addition to the average humidity (He, Yu, et al., 2017). The heat flux was at its highest levels in the initial stage and then decreased over time. This is because the substrate is initially exposed to direct sunlight and thus heats up more, but as the plants grow, they begin to shade the substrate, reducing the amount of heat that is absorbed (Mihalakakou, Souliotis, et al., 2023). Also, the heat flux differed depending on the type of heat, as the heat flux from sensible heat was higher than the heat flux from latent heat. From Figure 7, it is clear that heat flux is affected by soil conductivity and is higher in soils with high conductivity. Research has established a strong correlation between soil properties and the TP of GR in terms of their thermal ability to conduct heat and store heat (Berardi, GhaffarianHoseini, et al., 2014; Mihalakakou, Souliotis, et al., 2023). In both concentrated and broad GR frameworks, the pace of intensity transition of the soilless substrate is at half during the blooming stage (broad green roof) and the last stage because negligible foliage inclusion is answerable for unfolding water particles from leaves, while foliage inclusion and its concealing impact decrease reasonable intensity motion and sun powered radiation discharged by the substrate from the underlying stage to the reaping stage.

Figure 7. Rate of heat flux of soilless substrate under intensive green roof

Temperature Variations at Flowering Stage

The analysis results related to temperature variations at the flowering stage were obtained for all treatments (Figure 8), and it gradually increased from 0 am to 12 am, then peaking at 12 am to 2 pm, then decreased from 2 pm to 10 pm for both IGR and EGR with different treatments T₁ and T_2. Maximum substrate and foliage temperatures were 31.8°C (2 pm) and 30.3°C (2 pm) for treatments T₁ and T_2, respectively, during the IGR flowering stage. This confirms that EGR help reduce the temperature and thus cool the roofs during summer days (Huang, Chen, et al., 2018). The results from Figure 8 showed that the substrate temperature was higher than the foliage temperature and ambient temperature. This is because the substrate is exposed to direct sunlight and heated more. The foliage temperature is slightly higher than the ambient temperature because the foliage absorbs heat from sunlight. The temperature of the substrate and foliage decrease over time. This is because plants initiate transpiration which helps cool the plants while the ambient temperature remains relatively constant throughout the day.

Figure 8. Temperature variations at initial stage under EGR with soilless substrate

Intensive Green Roof (IGR)

The results of investigations into agricultural yield, energy balance, and temperature changes, especially related to the IGR systems, are presented to evaluate the economic sustainability of GR systems in Baghdad. The results indicated that until 2014, there was a specific increase in maximum and minimum temperatures throughout Baghdad. The results of some previous studies have confirmed that the temperature in Baghdad is increasing due to the lack of interest in GR systems (Anas and Yahya, 2023; Hassan and Husain, 2020). IGR systems reduce the temperature of bare roofs in summer. The LAI is recognized as one of the key plant characteristics that effectively affects the cooling performance of GRs. An increase in LAI enhances both LE and solar shading (Convertino, Schettini, et al., 2022). LAI observational data of tomato crop growth were used to study the cooling effect of IGR. LAI rose with crop growth in all treatments inside the IGR system where tomato crops were grown, according to observations. For both soilless and soil medium treatments, the maximum LAI values of 2.3 and 2.0 were attained during the harvesting stage, respectively. Subsequent research will examine the energy balance at the foliar level, taking into account elements like radiation exchange, sensible and latent heat flux, radiation absorption, and emission. It was observed that as the tomato crop progressed from the first to the harvesting stage, all of these components rose, with the latter stage showing the greatest values due to variables like increased LAI and L of vaporization at the foliage. These results are consistent with the results indicated by some studies, where they confirmed that as the LAI percentage increases, evaporation and shading increase, and thus the temperature decreases and cooling increases (Convertino, Schettini, et al., 2022; Dahanayake, Chow, et al., 2017).

Substrate conduction, radiation exchange, sensible and latent heat fluxes, and the energy balance at the substrate level were all investigated. According to the study, all of these factors declined as the tomato crop developed from the starting to the harvesting stages, with lower LAI initially leading to greater values being seen. In conclusion, the study looked at how the IGR system mitigates the UHI effect. The study found that the greatest temperature reductions occurred at 2:00 p.m. during the harvesting stage, with decreases of 3.5°C and 3.3°C observed in soilless and soil substrate media, respectively. Due to particular climatic conditions, the lowest heat flow (Q) through the roof was also measured at 2:00 pm, with greater values noted for soilless substrate. As far as harvest creation and water effectiveness, the investigation discovered that the soilless substrate treatment delivered the greatest tomato yield (4.4 kg/m²), while the dirt substrate treatment delivered 3.8 kg/m². Moreover, the treatment using soil substrate displayed predominant water productivity, estimating 0.86 kg/mm/m² rather than 0.74 kg/mm/m² for the treatment using soilless substrate.

Finally, tomato plants were chosen for this study to evaluate the cooling effects of IGR, as they exhibit rapid growth, produce dense canopy cover, and have a high rate of transpiration-all of which contribute significantly to evapotranspirative cooling. These characteristics make tomatoes an ideal model for assessing vegetation-driven thermal regulation in GR systems (Yang, Liu, et al., 2022).

Extensive Green Roof (EGR)

A number of important conclusions were made regarding the EGR used to grow marigold crops. As with the IGR, observations showed that the LAI increased with crop growth in all treatments. At the harvesting stage, the maximum LAI was roughly 0.5 for soil substrate treatments and 0.6 for soilless substrate treatments. In terms of energy balance components at the foliage level, the study found that, in the HGR with a soilless substrate, the greatest upsides of radiation trade among foliage and substrate, reasonable heat flux, LE at foliage, and long and short-wave radiation assimilated and transmitted by foliage were, separately, 184.6 W/m², 1.2 W/m², 5.2 W/m², and 935.7 W/m². The equivalent maximum values in the large-scale GR with soil substrate were roughly 178.2 W/m², 1.1 W/m², 4.0 W/m², and 782.9 W/m², in that order. Because soilless substrate treatments have higher LAI and L of vaporization at the leaves, they consistently show higher values in these energy balance components. The net Q was examined throughout the crop growth phases for treatments involving soil and soilless substrate. According to the study, the highest values were reached during the harvesting stage, coinciding with an increased temperature differential between the foliage and the substrate; the soilless substrate reached roughly 1126.0 W/m² and the soil substrate reached 966.2 W/m². These findings highlight the significant influence of LAI, enhanced plant growth, and substrate depth on energy conservation during both heating and cooling seasons (Silva, Gomes, et al., 2016).

The EGR with soilless substrate showed greatest upsides of 65.4 W/m², 40.0 W/m², 162.3 W/m², 672.1 W/m², and 4.4 W/m² for radiation trade among foliage and substrate, reasonable intensity motion, idle intensity transition, and substrate conduction, separately, as far as energy balance parts at the substrate level. For the HGR with soil substrate, the greatest qualities were generally 59.8 W/m², 36.0 W/m², 108.1 W/m², 610.2 W/m², and 3.8 W/m², in respective order. Again, soilless substrate medicines showed higher qualities, which were made sense of by various elements, including a smaller temperature gradient between the substrate and foliage, a more noteworthy shade impact, a reduction in wind speed, and idle intensity of vaporization at the substrate. The greatest qualities, estimating generally 488.8 W/m² for soilless substrate and 372.7 W/m² for soil substrate, were recorded at the underlying stage, as per the investigation of net intensity transition at the substrate level. This was principally a direct result of the concealing impact and the diminished temperature contrast among foliage and substrate at this stage.

Marigold was selected for this study on the effects of EGR due to its significant morphological diversity, rapid growth, adaptability, and high rate of transpiration, which can enhance the cooling effects of GRs. These characteristics are advantageous for GR applications (Cominelli and Patrignani, 2022; Sooriyapathirana, Ranaweera, et al., 2021).

Comparison of Two Green Roof Systems

At 2:00 pm, the IGR showed the greatest reduction of the UHI effect, much like the intensive one did. At the marigold crop's harvesting stage, temperature decreases of 2.8^oC and 2.6^oC, respectively, were noted for soilless and soil substrate media throughout this period. Furthermore, at 2:00 pm, the lowest heat flux through the roof was recorded, showing that soilless substrate conditions are crucial in producing these effects. The measured heat flux values were 8.6 W/m² for the soilless substrate and 6.3 W/m² for the soil substrate media.

To sum up, this study has produced insightful information, especially on GR systems and how they affect thermal performance and energy efficiency. A streamlined approach was created to evaluate the thermal behavior of various GR systems, emphasizing extensive and intensive variations. The results highlight how important GRs are for reducing heat flux in poorly insulated buildings, with larger roof substrates resulting in more heat reduction. It was discovered that the amount of moisture in the soil and how that moisture affected evapotranspiration were important variables, with dryer soil types providing better thermal insulation (Mahmoodzadeh, Mukhopadhyaya, et al., 2020). Both comprehensive and IGR solutions improve energy and environmental efficiency, according to the study. It has been demonstrated that both systems dramatically lower temperatures by roughly 3.5 and 3.3^oC, respectively, which helps to mitigate the UHI effect and affects the roof's outer surface temperature. Because of their higher LAI and thicker substrate, IGR, in particular, has shown greater thermal efficiency in terms of reducing heat flux through the roof and the UHI effect. A multi-criteria comparison was carried out to assess the energy and environmental performance of the two GR systems. Based on a comparative investigation, IGRs are the most efficient technique for lowering building cooling energy demands and mitigating the effects of UHI, especially in semi-arid climates like Baghdad.

The results indicate that GRs have an effective and positive role in the ecology or economy and extend over long periods.

The most important of these ecological benefits is that GRs help reduce CO₂ emissions and GHG emissions. GRs also help reduce temperatures by covering the roofs and providing insulation, which allows winter heating or summer cooling. Green roofs reduce rainwater runoff, which helps relieve pressure on sewage drains. They play a role in improving and purifying air quality. These roofs provide space for food production, biodiversity, and beautiful environmental views.

The most important of these economic benefits is the saving of energy through insulation. Additionally, the presence of these roofs extends the life of buildings by protecting them from ultraviolet rays and temperature changes. Also, air quality and purity play a role in the overall health of the people living in these buildings, reducing the need for health care and spending money (Li and Babcock, 2014; Perivoliotis, Arvanitis, et al., 2023; Shahmohammad, Hosseinzadeh, et al., 2022; Wang, Guo, et al., 2024).

While the single-layer vegetation model offers a simplified representation of GR systems, it effectively captures essential thermal processes and serves as a solid foundation for evaluating baseline performance. To enhance thermal predictions-especially in green roofs with high biodiversity or complex architectural features, future studies could integrate multi-layer vegetation dynamics and species-specific physiological traits. Advanced energy balance models such as SVAT, ENVI-met, and CFD have been employed in numerous studies to simulate the intricate interactions and vertical structure of multilayered green roofs with varied vegetation types (Alexandri and Jones, 2008; Iwata and Shimoda, 2024; Perini and Magliocco, 2014; Vilar, Tello, et al., 2021). In contrast, this study utilized the single-layer model due to its emphasis on fundamental thermal behavior and certain constraints related to computational and data resources.

While this study primarily examined thermal performance and structural capacity, these findings directly support potential economic benefits, particularly in reducing energy demand and prolonging roof lifespan. Future work should integrate detailed cost-benefit analyses, including installation, maintenance, and operational savings, to fully capture the long-term economic sustainability of GR systems in arid and semi-arid contexts.

Conclusion and Future Work

The current study focuses on evaluating the ecological and economic sustainability of GR systems, including HGR, IGR, and EGR. The results obtained confirmed that GRs play an important role in reducing heat flux in buildings with insufficient insulation and stressing that larger roof substrates result in more significant heat reduction. In addition, it was found that soil moisture and LAI significantly affect latent heat evaporation, thus increasing the cooling effect of GRs. Furthermore, the results confirmed that GRs with IGR, and EGR significantly improve environmental and energy performance and reduce temperatures, as these lower temperatures affect the external surface temperature of the roofs and help mitigate the UHI effect. The results of evaluating green roof systems' energy and environmental performance also showed that IGRs have better thermal performance than other GRs due to the higher LAI and thicker substrate. Finally, according to the results of this study, IGRs are a more practical technology for reducing building cooling energy requirements and reducing UHI impacts, especially in semi-arid climates such as Baghdad.

Although this study offers strong evidence of the thermal and energy efficiency advantages of IGR systems, especially within semi-arid urban settings, broadening future investigations to include a wider range of urban environments could enhance the dataset and strengthen the generalizability of the results. Such an expansion would offer more nuanced understanding of regional differences and reinforce the real-world relevance of implementing green roofs on a larger scale. Undertaking a thorough analysis of GRs with respect to their thermal efficiency and financial feasibility on freshly built or existing roofs on a wider scale may provide insightful information and useful applications. A major area of future research is investigating different models of energy balance. Through the utilization of various models, it is feasible to maximize the thermal advantages of green roof systems, augmenting their efficacy and efficiency in reducing heat flux. There would be great opportunity for a biometric study that focuses on the various vegetation layers found on green roofs. Researching the precise function that different plant species and their combinations play in lowering heat flux inside the roof structure might help designers create green roofs that are more specialized and efficient. All parameters that must be considered, as well as these new avenues for research, should help us better understand the TP, EE, and environmental impact of GRs. Although this study was limited to a single-layer vegetation system, it provided valuable baseline insights into species-specific contributions to heat flux reduction under semi-arid conditions. However, GRs in practice often feature multi-layered, mixed-species plantings that interact in complex ways to enhance cooling and resilience. Therefore, future research should prioritize stratified vegetation designs and species groupings, particularly in climates subject to extreme heat and water scarcity. Understanding these plant interactions will be critical for optimizing GR design and maximizing thermal performance and resource efficiency.

Researchers also recommend conducting future studies over long periods of time and linking their results to the results of this study, and creating a timeline that shows the ecological and economic impacts of GRs in order to benefit from them in the future.

Author Contributions

Conceptualization, methodology, software, investigation, resources, data curation, writing-original draft preparation, writing-review and editing and supervision, Z.M.A., M.T.A. and A.K.A. All authors have read and agreed to the published version of the manuscript.

Ethics Declaration

The authors declare that they have no conflicts of interest regarding the publication of the paper.

Funding

This research received no external funding.

References

•  Abdulrazzaq,  Z. (2025). "Sustainable landscape design and planning for campus: a comparative study of implementation strategies". Anbar Journal of Agricultural Sciences, 23(2).
•  Abdulrazzaq,  Z.,  Ahmed , M. S., et al. (2020). "Rock gardens planning and designing-theory and application". Indian Journal of Ecology, 47, 85–91.
•  Abdulrazzaq , Z. M.,  Al-Abdaly , H. M., et al. (2024). "Sustainable Outdoor Spaces and Their Achievement Mechanisms at the University Campus Case Study - University of Anbar". AIP Conference Proceedings, 2885, 020016. doi: https://doi.org/https://doi.org/10.1063/5.0181570
•  Aini,  N.,  Wikantiyoso,  R., et al. (2025). "Monitoring urban microclimates using Computational Fluid Dynamics ( CFD ) simulations". International Review for Spatial Planning and Sustainable Development, 13(2), 219–234.
•  Alexandri,  E., and  Jones,  P. (2008). "Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates". Building and Environment, 43(4), 480–493. doi: https://doi.org/10.1016/j.buildenv.2006.10.055
•  Anas,  K., and  Yahya, I, . (2023). "The Effect of Green Roof on Thermal Comfort of Individual Housing Units in Hot and Arid Climates (A Case Study in Baghdad -Field Application)". AIP Conference Proceedings, 1–14.
•  Berardi,  U.,  GhaffarianHoseini,  A., et al. (2014). "State-of-the-art analysis of the environmental benefits of green roofs". Applied Energy, 115, 411–428. doi: https://doi.org/10.1016/j.apenergy.2013.10.047
•  Borghei,  S.,  Niroumand,  N., et al. (2025). "The Impact of Green Roofs and Internal Patios on Energy Consumption in a School Building". International Review for Spatial Planning and Sustainable Development, 13(2), 7–24. doi: https://doi.org/10.14246/irspsd.13.2_7
•  Buckley,  S.,  Connolly , C. L., et al. (2023). "Carbon, indoor air, energy and financial benefits of coupled ventilation upgrade and enhanced rooftop garden installation: An interdisciplinary climate mitigation approach". Sustainable Cities and Society, 97, 104792. doi: https://doi.org/10.1016/j.scs.2023.104792
•  Chen,  P.-Y. (2022). "Effects of meteorological variables and substrate moisture on evapotranspiration and thermal performance of a green roof in a subtropical climate". Ecological Engineering, 180, 106663. doi: https://doi.org/10.1016/j.ecoleng.2022.106663
•  Cominelli,  S., and  Patrignani,  A. (2022). Transpiration response of palmer amaranth (Amaranthus palmeri) to drying soil in greenhouse conditions. Frontiers in Agronomy, 4, 1018251.
•  Convertino,  F.,  Schettini,  E., et al. (2022). Effect of Leaf Area Index on Green Facade Thermal Performance in Buildings. Sustainability, 14(5), 2966.
•  Dahanayake , K. C.,  Chow , C. L., et al. (2017). Selection of suitable plant species for energy efficient Vertical Greenery Systems (VGS). Energy Procedia, 142, 2473–2478. https://doi.org/https://doi.org/10.1016/j.egypro.2017.12.185
•  Donald , W. M.,  Jean,  S., et al. (2011). "Statistical analysis for monotonic trends". Tech Notes 6. Developed for U.S. Environmental Protection Agency by Tetra Tech, Inc. Availabel at https://www.epa.gov/polluted-runoff-nonpoint-source-pollution/nonpoint-source-monitoringtechnical-notes
•  Dwivedi,  A., and  Mohan , B. K. (2018). "Impact of green roof on micro climate to reduce Urban Heat Island". Remote Sensing Applications: Society and Environment, 10, 56–69. doi: https://doi.org/10.1016/j.rsase.2018.01.003
•  Fei,  Y.,  Fu,  D., et al. (2023). "Component design optimization of green roof substrate layer based on the assessment of multifunctional performance". Environmental Research, 238, 117190. doi: https://doi.org/10.1016/j.envres.2023.117190
•  Harris,  M. (2014). "The GRO Green Roof Code-Green Roof Code of Best Practice for the UK 2014". Groundwork Sheffield, 1–35.
•  Hassan , S. A., and  Husain , S. I. (2020). "The effect of green roof on improving the environmental efficiency for the residential buildings in Baghdad city". IOP Conference Series: Materials Science and Engineering, 928(2), 022011. doi: https://doi.org/10.1088/1757-899X/928/2/022011
•  He, Y.,  Yu,  H., et al. (2017). "Influence of plant and soil layer on energy balance and thermal performance of green roof system". Energy, 141, 1285–1299. doi: https://doi.org/10.1016/j.energy.2017.08.064
•  Huang,  Y.-Y.,  Chen,  C.-T., et al. (2018). "Thermal performance of extensive green roofs in a subtropical metropolitan area". Energy and Buildings, 159, 39–53. doi: https://doi.org/10.1016/j.enbuild.2017.10.039
•  Hussien,  A.,  Jannat,  N., et al. (2023). "A holistic plan of flat roof to green-roof conversion: Towards a sustainable built environment". Ecological Engineering, 190, 106925. doi: https://doi.org/10.1016/j.ecoleng.2023.106925
•  Iwata,  T., and  Shimoda,  R. (2024). "Spontaneous vegetation in mandatory green roofs at public educational facilities in Sumida-ku, Tokyo". Landscape Research Japan Online, 17, 38–46. doi: https://doi.org/10.5632/jilaonline.17.38
•  Jamei,  E.,  Chau , H. W., et al. (2023). "Green roof and energy – role of climate and design elements in hot and temperate climates". Heliyon, 9(5), e15917. doi: https://doi.org/10.1016/j.heliyon.2023.e15917
•  Jumaah , M. S.,  Abdulrazzaq , Z. M., et al. (2021). "Role of Green Spaces and Their Impact on Climate Design and Ecosystem Efficienc". IOP Conference Series: Earth and Environmental Science, 761(1), 012055. doi: https://doi.org/https://doi.org/10.1088/1755-1315/761/1/012055
•  Kazemi,  M.,  Rahif,  R., et al. (2023). "Sensitivity analysis and weather condition effects on hygrothermal performance of green roof models characterized by recycled and artificial materials’ properties". Building and Environment, 237, 110327. doi: https://doi.org/10.1016/j.buildenv.2023.110327
•  Kim , S. W., and  Brown , R. D. (2021). "Urban heat island (UHI) variations within a city boundary: A systematic literature review". Renewable and Sustainable Energy Reviews, 148, 111256. doi: https://doi.org/10.1016/j.rser.2021.111256
•  Lee, L. S. H. , and  Jim,  C. Y., (2020). "Thermal-irradiance behaviours of subtropical intensive green roof in winter and landscape-soil design implications". Energy and Buildings, 209, 109692. doi: https://doi.org/10.1016/j.enbuild.2019.109692
•  Li, Y., and  Babcock , R. W. (2014). "Green roofs against pollution and climate change. A review". Agronomy for Sustainable Development, 34(4), 695–705. doi: https://doi.org/10.1007/s13593-014-0230-9
•  Li, Y., and  Liu,  J. (2023). "Green roofs in the humid subtropics: The role of environmental and design factors on stormwater retention and peak reduction". Science of The Total Environment, 858, 159710. doi : https://doi.org/10.1016/j.scitotenv.2022.159710
•  Liu,  H.,  Kong,  F., et al. (2021). "Impacts of green roofs on water, temperature, and air quality: A bibliometric review". Building and Environment, 196, 107794. doi: https://doi.org/10.1016/j.buildenv.2021.107794
•  Mahmoodzadeh,  M.  Mukhopadhyaya,  P., et al. (2020). "Effects of Extensive Green Roofs on Energy Performance of School Buildings in Four North American Climates". Water, 12(1), 6. doi: https://doi.org/10.3390/w12010006
•  Mahmoudi,  A.,  Mousavi , S. A., et al. (2021). Greywater as a sustainable source for development of green roofs: Characteristics, treatment technologies, reuse, case studies and future developments. Journal of Environmental Management, 295, 112991. doi: https://doi.org/10.1016/j.jenvman.2021.112991
•  Malamis,  S.,  Katsou,  E., et al. (2016). "Chapter 5 - Urban Environment". In Poulopoulos Inglezakis (Eds.), Environment and Development: Basic Principles, Human Activities, and Environmental Implications, 287–362. Elsevier. doi: https://doi.org/10.1016/B978-0-444-62733-9.00005-8
•  Mihalakakou,  G.,  Souliotis,  M., et al. (2023). "Green roofs as a nature-based solution for improving urban sustainability: Progress and perspectives". Renewable and Sustainable Energy Reviews, 180, 113306. doi: https://doi.org/10.1016/j.rser.2023.113306
•  Perini,  K., and  Magliocco,  A. (2014). "Effects of vegetation, urban density, building height, and atmospheric conditions on local temperatures and thermal comfort". Urban Forestry & Urban Greening, 13(3), 495–506. doi: https://doi.org/10.1016/j.ufug.2014.03.003
•  Perivoliotis,  D.,  Arvanitis,  I., et al. (2023). "Sustainable Urban Environment through Green Roofs: A Literature Review with Case Studies". Sustainability, 15(22), 15976. doi: https://doi.org/10.3390/su152215976
•  Prall,  M.,  Olazabal,  M., et al. (2023). "Socio-economic projections in urban climate change adaptation planning: Practices and prospects for just adaptation". Habitat International, 142, 102946. doi: https://doi.org/10.1016/j.habitatint.2023.102946
•  Pumo,  D.,  Alongi,  F., et al. (2023). "Climate adaptive urban measures in Mediterranean areas: Thermal effectiveness of an advanced multilayer green roof installed in Palermo (Italy)". Building and Environment, 243, 110731. doi: https://doi.org/10.1016/j.buildenv.2023.110731
•  Pumo,  D.,  Francipane,  A., et al. (2023). "The potential of multilayer green roofs for stormwater management in urban area under semi-arid Mediterranean climate conditions". Journal of Environmental Management, 326, 116643. doi: https://doi.org/10.1016/j.jenvman.2022.116643
•  Qian,  J.,  Meng,  Q., et al. (2023). "Characteristics of anthropogenic heat with different modeling ideas and its driving effect on urban heat islands in seven typical Chinese cities". Science of The Total Environment, 886, 163989. doi: https://doi.org/10.1016/j.scitotenv.2023.163989
•  Salvalai,  G.,  Marrone,  G., et al. (2023). "Lightweight extensive green roof for building renovation: Summer performance analysis and application in a living laboratory". Energy and Buildings, 298, 113589. doi: https://doi.org/10.1016/j.enbuild.2023.113589
•  Sen , P. K. (1968). "Estimates of the Regression Coefficient Based on Kendall’s Tau". Journal of the American Statistical Association, 63(324), 1379–1389. doi: https://doi.org/10.1080/01621459.1968.10480934
•  Seyedabadi , M. R.,  Eicker,  U., et al (2021). "Plant selection for green roofs and their impact on carbon sequestration and the building carbon footprint". Environmental Challenges, 4, 100119. doi: https://doi.org/10.1016/j.envc.2021.100119
•  Shahmohammad,  M.,  Hosseinzadeh,  M., et al. (2022). "Sustainable green roofs: a comprehensive review of influential factors". Environmental Science and Pollution Research, 29(52), 78228–78254. doi: https://doi.org/10.1007/s11356-022-23405-x
•  Silva , C. M.,  Gomes , M. G., et al. (2016). "Green roofs energy performance in Mediterranean climate". Energy and Buildings, 116, 318–325. doi: https://doi.org/10.1016/j.enbuild.2016.01.012
•  Sooriyapathirana , S. D. S. S.,  Ranaweera , L. T., et al (2021). "Photosynthetic Phenomics of Field- and Greenhouse-Grown Amaranths vs. Sensory and Species Delimits". Plant Phenomics, 2021, 2539380. doi: https://doi.org/10.34133/2021/2539380
•  Taguchi,  M., and  Kikuchi,  S. (2015). "The Current Status of Green Roof Policy, By-laws, Regulations, Incentives in North America". Reports of the City Planning Institute of Japan, 14(1), 51–54. doi: https://doi.org/10.11361/reportscpij.14.1_51
•  Talwar,  P.,  Verma,  N., et al. (2023). "A systematic review of photovoltaic-green roof systems in different climatic conditions focusing on sustainable cities and societies". Sustainable Cities and Society, 98, 104813. doi: https://doi.org/10.1016/j.scs.2023.104813
•  Tan,  T.,  Kong,  F., et al. (2023). "Carbon dioxide reduction from green roofs: A comprehensive review of processes, factors, and quantitative methods". Renewable and Sustainable Energy Reviews, 182, 113412. doi: https://doi.org/10.1016/j.rser.2023.113412
•  Tighnavard  Balasbaneh, A., Sher., W., et al. (2024). "Life cycle sustainability assessment of alternative green roofs – A systematic literature review". Building and Environment, 248, 111064. doi: https://doi.org/10.1016/j.buildenv.2023.111064
•  Viecco,  M.,  Jorquera,  H., et al. (2021). "Green roofs and green walls layouts for improved urban air quality by mitigating particulate matter". Building and Environment, 204, 108120. doi: https://doi.org/10.1016/j.buildenv.2021.108120
•  Vilar , M.  L.,  Tello, L., et al. (2021). "An energy balance model of heterogeneous extensive green roofs". Energy and Buildings, 250, 111265. doi: https://doi.org/10.1016/j.enbuild.2021.111265
•  Wang,  C.,  Guo,  J., et al. (2024). "Green roofs and their effect on architectural design and urban ecology using deep learning approaches". Soft Computing, 28(4), 3667–3682. doi: https://doi.org/10.1007/s00500-024-09637-8
•  Wei , Y. D.,  Xiong,  N., et al. (2023). "Urban space, sprawl, and intergenerational mobility". Applied Geography, 156, 102991. doi: https://doi.org/10.1016/j.apgeog.2023.102991
•  Wikantiyoso,  R., and  Tutuko,  P. (2013). "Planning Review: Green City Design Approach for Global Warming Anticipatory: Surabaya’s Development Plan". International Review for Spatial Planning and Sustainable Development, 1(3), 4–18. doi: https://doi.org/10.14246/irspsd.1.3_4
•  Wong G. K. L., and  Jim, C. Y., (2015). "Identifying keystone meteorological factors of green-roof stormwater retention to inform design and planning". Landscape and Urban Planning, 143, 173–182. doi: https://doi.org/10.1016/j.landurbplan.2015.07.001
•  Wooster , E. I. F.,  Fleck,  R., et al. (2022). "Urban green roofs promote metropolitan biodiversity: A comparative case study". Building and Environment, 207, 108458. doi: https://doi.org/10.1016/j.buildenv.2021.108458
•  Yang,  L.,  Liu,  H., et al. (2022). "Microclimate and Plant Transpiration of Tomato (Solanum lycopersicum L.) in a Sunken Solar Greenhouse in North China". Agriculture, 12(2), 260. doi: https://doi.org/10.3390/agriculture12020260
•  Yousaf  Raza,  M.,  Hasan, M. M., et al. (2023). "Role of economic growth, urbanization and energy consumption on climate change in Bangladesh". Energy Strategy Reviews, 47, 101088. doi: https://doi.org/10.1016/j.esr.2023.101088
•  Zheng,  S.,  Chen,  X., et al. (2023). "Impact of urban renewal on urban heat island: Study of renewal processes and thermal effects". Sustainable Cities and Society, 99, 104995. doi: https://doi.org/10.1016/j.scs.2023.104995
•  Zheng,  X.,  Kong,  F., et al. (2023). "Green roof cooling and carbon mitigation benefits in a subtropical city. Urban Forestry & Urban Greening", 86, 128018. doi: https://doi.org/10.1016/j.ufug.2023.128018
•  Zuberbier,  T.,  Stevanovic,  K., et al. (2024). "Green Roof Gardens – Selecting Allergy-Friendly Vegetation: A Global Allergy and Asthma Excellence Network (GA²LEN) Position Paper". The Journal of Allergy and Clinical Immunology: In Practice, 12(2), 347–354. doi: https://doi.org/10.1016/j.jaip.2023.10.028