Integrating Green Infrastructure into Environmental Planning: A DesignBuilder-Based Assessment

Green infrastructure has been noted in environmental planning as a strategically managed bundle of natural or semi-natural areas such as parks, green roofs, and wetlands that offer ecological, social, and economic benefits. This type of infrastructure offers advantages such as biodiversity, stormwater management, air quality improvement, and overcoming the impacts of climate change [6].

The use of green infrastructure is essential for increasing the functioning of urban ecosystems. It is known to increase a number of ecosystem services, for instance, biodiversity enhancement, mitigation of urban heat island effects, improvement of air quality, and so on [7]. Through an analysis of different green infrastructure, such as urban forests, permeable pavements, green walls, and green roofs, this paper seeks to determine the different benefits associated with urban green infrastructure. Different forms of green infrastructure, such as urban forests, permeable pavements, green walls, and green roofs, enable local administrations to improve water quality, manage stormwater runoff, reduce flood risk, decrease heat stress, support carbon storage, and enhance urban livability [8].

Green infrastructure has emerged as a key component of these frameworks, which is not only described as urban greenery but as a connected system that provides ecological, social, and climatic benefits [9]. Unlike traditional infrastructure, green infrastructure can play a role in the management of stormwater, temperature regulation, air quality improvement, as well as biodiversity conservation, while improving urban livability [10].

Most of the planning literature remains conceptual, discussing policy instruments and governance strategies while not quantitatively linking planning decisions to environmental performance at the building level.

For instance, green roofs can be cited as a popular form of green infrastructure typology whose performance varies greatly depending on the nature of systems being employed. Large green roof systems are commonly applied for stormwater management and insulation purposes due to their lightweight and low-maintenance plant species, despite having a very shallow growing medium layer. In contrast, intensive green roofs require greater structural support and maintenance while offering more thermal mass, shading, and cooling capabilities (Table 1).

Table 1. Extensive vs. intensive green roof case studies (Europe & North America)

Aspect	Extensive Green Roof Case Studies	Intensive Green Roof Case Studies
Definition	Lightweight, maintenance-free, and shallow substrate systems are mainly designed for environmental benefits.	Complexly structured, deep substrate systems capable of sustaining trees, shrubs, and functional spaces.
Chicago, USA	Sedum and grass are planted as experimental cooling and stormwater management solutions on the City Hall roof (extensive areas).	Deep soil that can accommodate grass, trees, and recreational spaces is found in Millennium Park and the City Hall intensive areas.
	index-2_1.jpg	index-2_2.jpg
Stuttgart, Germany	index-2_3.jpg	index-2_4.jpg
	Stuttgart industrial, residential, and garage roofs (city-wide program)	Calwer Passage redevelopment (ingenhoven architects)
North America	index-2_5.jpg	index-2_6.jpg
	Gary Comer Youth Center — Chicago	Morgan North Rooftop Park — New York City

Green roofs significantly improve the environmental performance of buildings by up to 70% in terms of cooling load reduction, decrease in roof surface temperature, and enhanced insulation. They control stormwater, retaining 60% to 100% of rainfall; air pollutants are filtered, and the heat island effects within cities are minimized; all this while protecting membranes for extended life [12].

Green roofs have a positive impact on indoor and outdoor thermal comfort. The environmental changes that reduce outdoor temperature levels will decrease summer surface heat, along with cooling system requirements. Researchers [13] have conducted multiple studies to determine the level of comfort that exists between indoor and outdoor environments.

Green roofs affect building energy use through multiple operational systems, which include plant water release and solar heat absorption in leaves and air movement for heat transfer and earth temperature regulation, and water loss from soil surfaces [14]. Green roofs affect building energy use through several physical mechanisms, including evapotranspiration, solar radiation absorption, convective heat transfer, soil heat storage, and moisture exchange [14, 15]. These mechanisms are schematically illustrated in Figure 1.

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Research indicates that green roofs help to reduce surface temperatures, while shading systems and vegetation help to reduce solar heat gains. Urban trees and landscape also help to reduce extremes of microclimate and improve outdoor thermal comfort [14].

However, research on these techniques is mostly conducted on a standalone basis, focusing on individual buildings, rather than integrating these techniques within a wider environmental planning strategy, including aspects such as neighbourhood arrangement, spatial orientation, density patterns, and land use planning strategies.

6.1 Research methodology

This study, consistent with common DesignBuilder–Energy Plus simulation practice, was conducted on the Al-Khwarizmi College of Engineering building at the University of Baghdad. The paper quantifies the impacts of the green infrastructure approach on the performance of the environment, including alleviating heat in urban areas, enhancing thermal comfort, lowering the carbon footprint, and improving energy efficiency. This proposed methodology facilitates decision-making regarding the development of sustainable urban policy solutions because it makes comparisons among different scenarios easier. This methodology is an enhancement to the previous simulation-based research on sustainability performance evaluation using DesignBuilder simulations.

The research utilizes the simulation-based DesignBuilder software for analysis to evaluate the impact of the chosen green infrastructure on the environment. As part of efforts aimed at enhancing sustainable urban planning and design, the evaluation highlights important performance indicators, including energy usage, comfort, emissions, and urban cooling, as shown in Figure 2.

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Figure 2. Methodological framework for the development and application of integrated green infrastructure performance

6.2 Research approach

In order to assess how well green infrastructure initiatives improve environmental performance within environmental planning frameworks, this study uses a quantitative simulation-based methodology. The study uses DesignBuilder software, which is driven by the Energy Plus calculation engine, to simulate dynamic building energy. The method makes it possible to compare several green infrastructure intervention scenarios under local climate circumstances in Baghdad, Iraq, with a baseline scenario.

6.3 Climate data and weather file

An Energy Plus-compatible typical meteorological year (TMY) weather file provided hourly climate data for Baghdad. Baghdad’s climate is low-latitude, arid, hot, and subtropical (Köppen-Geiger classification: BWh). The monthly climate profile is presented in Figure 3. The climate data used in the simulation include:

• Dry bulb temperature
• Relative humidity
• Radiation from the sun
• Wind direction and speed

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6.4 Baghdad climate and temperature profile

Baghdad, Iraq, is characterized by a hot-dry climate with high summer temperatures and strong solar radiation. The average annual temperature is approximately 22.8 ℃ (73 °F). Monthly average temperatures vary throughout the year, with the lowest average temperature occurring in January at about 10 ℃ (50 °F), while the highest average temperature occurs in August at approximately 34.5 ℃ (94.1 °F). The monthly variations in Baghdad’s maximum, average, and minimum temperatures are illustrated in Figure 4.

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Figure 4. Baghdad average temperatures chart

These climatic conditions increase cooling energy demand and make the case study suitable for evaluating green infrastructure and passive design strategies under hot-arid environmental conditions. The temperature data presented in Table 2 were obtained from Climate-Data.org.

Table 2. Baghdad, Iraq's average monthly temperature data, ℃ (°F)

DesignBuilder provides people with an easy-to-use software platform that enables them to create building energy consumption models and perform simulation studies that analyze their energy usage. The software performs thermal, lighting, and energy simulations by connecting with other programs, which include Energy Plus and Radiance. Designers must create detailed three-dimensional building models in DesignBuilder to achieve optimal energy efficiency, comfort, and sustainable design practices. The software receives extensive usage from architects and sustainability consultants who work in their respective fields, see Figure 8.

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Figure 8. Practical research methodology framework

The baseline model developed was validated through comparison with the actual energy consumption values of the selected building. Monthly electrical energy consumption data obtained from the building administration were used for the comparison with the simulation results generated by the Energy Plus calculation engine.

For the purpose of minimizing the difference between the two sets of values, it was necessary to change some input parameters, such as occupancy schedules, lighting load, equipment load, infiltration rate, and heating, ventilation, and air-conditioning (HVAC) system operation characteristics. The calibration and validation of the building energy model followed Guideline 14 of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

The normalized mean bias error (NMBE) and the coefficient of variation of the root mean square error (CV(RMSE)) were calculated using Eqs. (1) and (2), respectively:

$\operatorname{NMBE}(\%)=\frac{\sum_{i=1}^n\left(M_i-S_i\right)}{(n-p) \bar{M}} \times 100$              (1)

$\operatorname{CV}(\operatorname{RMSE})(\%)=\frac{\sqrt{\frac{\sum_{i=1}^n\left(M_i-S_i\right)^2}{n-p}}}{\bar{M}} \times 100$               (2)

where,

$n$ is the number of data points;

$p$ is the number of corrected or adjustable model parameters;

$M_i$ is the measured energy consumption at time interval $i$;

$S_i$ is the simulated energy consumption at time interval $i$;

$\bar{M}$ is the average measured energy consumption.

ASHRAE Guideline 14 provides recommended acceptable limits for monthly model calibration. In this study, model credibility was established through comparative analysis with simulation experiments reported in existing literature under similar climatic conditions, as operational monitoring data for the case study building were not available. Consequently, statistical indices such as the root mean square error (RMSE), NMBE, CV(RMSE), and coefficient of determination (R²) could not be computed. This represents a limitation of the study, and future work will seek to collect measured building performance data to enable full quantitative validation in accordance with ASHRAE Guideline 14. The simulation model was therefore considered sufficiently representative for the comparative assessment of the proposed green infrastructure scenarios.

The design process of building envelope components, along with their material properties, requires designers to generate thermal data, which Energy Plus needs for its calculation engine. The modelling process required DesignBuilder to develop precise envelopes, which included walls and roofs, floors and glazing systems, and shading elements to match actual building construction methods. The DesignBuilder software performs hourly calculations to determine heat transfer and solar gains, thermal mass effects, and cooling requirements. The establishment of a dependable baseline model in DesignBuilder allows users to perform systematic comparisons between current conditions and future green infrastructure scenarios. The evaluation system will show all changes in energy usage, indoor temperature comfort, and carbon emissions that result from changes to building envelopes and designs rather than from modelling assumptions. The simulation-based method produces better results for environmental performance assessment because it creates more dependable and repeatable results, which help people make smarter decisions.

8.1 Building simulation

The simulation used DesignBuilder's graphical user interface version V7, which runs Energy Plus calculation engines. The DesignBuilder selection process involved choosing this software because it allowed users to enter flexible geometry data while providing a wide range of materials and load profile options. The system contains control methods that verify that output results match the results produced by independent Energy Plus engines. The Design-Builder program performed simulations that tested cooling and heating system usage to determine how well the building performed, as shown in Figure 9.

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Figure 9. Sun-path diagrams of the case-study building generated using DesignBuilder: (a) plan view and (b) three-dimensional view

The specifications satisfy the Al-Khwarizmi College of Engineering at the University of Baghdad and are consistent with Energy Plus modelling and hot-dry climate performance. According to earlier studies, the thermal performance of a wall can be enhanced by implementing a multilayered wall construction with different thermal properties. In order to examine their thermal performance, five different building techniques were chosen for this study and applied to a building in the Al-Khwarizmi College of Engineering as a Base Case model. The model was created, and the opaque wall on the south façade was modified utilizing a variety of ways, including layers of materials, while taking into account the manufacturer's dimensions, thickness, and material qualities, as shown in Table 3.

Table 3. Construction layers of the Base Case of the Al-Khwarizmi College of Engineering at the University of Baghdad

8.2 S1: Green roof scenario

In order to assess how well vegetated roofing systems work as a passive environmental strategy to enhance building thermal performance in hot, dry climates, the Green Roof Scenario was created. In this case, a comprehensive green roof system that included layers of vegetation, growing media, drainage, and waterproofing was used in place of the traditional roof construction of the University of Baghdad's Department of Al-Khwarizmi College. By using shading, more thermal mass, and evapotranspiration processes, the technique seeks to lower roof surface temperatures, postpone heat transfer into interior rooms, and lessen peak cooling loads.

Table 4. Input parameters of the DesignBuilder simulation

Table 5. Parameters of high-performance building envelope

Table 6. Input parameters of green roof - DesignBuilder simulation

The baseline and green-roof construction assemblies are compared in Figure 10, while the plan layout and three-dimensional model of the green-roof scenario are presented in Figure 11.

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Figure 10. Conventional case vs. green roof case (DesignBuilder screenshot)

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Figure 11. (a) Layout, (b) 3D view of green roof case

Energy Plus-based surface heat balance calculations were used to simulate the green roof in DesignBuilder. Changes were made to the exterior surface parameters, material thermal values, and roof construction layers. In order to directly compare the scenario with the baseline roof configuration, it was simulated under local climate conditions to measure its effects on indoor thermal comfort, annual cooling energy use, and related carbon emissions (see Tables 4, 5, and 6). The principal DesignBuilder input parameters adopted for the green-roof simulation are summarized in Table 6.

The soil depth of the virtual green roof was about 150 mm, which was considered normal for green roofs that would be deployed in very hot regions on a larger scale. Drought-resistant grass as well as native plants, which could easily adapt to dry environments, formed the vegetation cover. The model used for simulation adopted an average plant height of 0.20 m and a Leaf Area Index (LAI) of 2.5. For maintaining vegetative efficiency under the very hot conditions of Baghdad, minimal watering was allowed in the summer months.

8.3 S2: High-performance building envelope

To evaluate the effects of improved thermal building envelope characteristics on energy efficiency and indoor environmental quality in hot, dry climates, the High-Performance Building Envelope Scenario was created.

The baseline envelope of Al-Khwarizmi College of Engineering at the University of Baghdad was improved in this scenario by increasing the amount of insulation on the walls and roof, improving the performance of the glass, and improving the solar control features. Reducing radiative and conductive heat gains via the building envelope is the goal in order to improve indoor thermal comfort and lower the energy demand for cooling, as illustrated in Table 5. This scenario was implemented in DesignBuilder by altering envelope construction assemblies and material thermal properties, such as decreased thermal conductivity (U-values), increased insulation thickness, and optimized surface solar absorptance, see Figure 12. The improved envelope's steady-state and dynamic thermal behavior under local weather conditions were simulated using Energy Plus heat transfer algorithms. In order to ascertain the relative efficacy of this scenario, its performance was assessed in terms of annual cooling energy consumption, indoor operative temperature, thermal comfort indices—Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD)—and carbon dioxide emissions. It was then directly compared with the baseline and green roof scenarios.

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Figure 12. Conventional wall vs development wall (Design-Builder screenshot)

8.4 S3: Natural ventilation strategy scenario

The Natural Ventilation Strategy Scenario was created to evaluate how passive airflow systems could enhance indoor comfort through natural ventilation while cutting down on cooling power requirements during hot-dry climate conditions. Al-Khwarizmi College of Engineering at the University of Baghdad modified its baseline mechanical ventilation and infiltration assumptions to create a system that would allow students to control natural ventilation through their window operations and their ability to open windows. The strategy works to boost air circulation while it enables heat discharge when weather conditions are suitable, and it seeks to decrease the need for mechanical cooling systems

By defining operable window properties, modifying opening schedules, and turning on airflow network modelling based on Energy Plus algorithms, natural ventilation was implemented within DesignBuilder. Important factors included wind-driven and buoyancy-driven airflow effects, window opening control logic connected to indoor-outdoor temperature differentials, and ventilation operation at night during colder temperatures. To assess the scenario's effects on indoor operating temperature, thermal comfort indices (PMV/PPD), ventilation rates, and annual cooling energy consumption, local climate data were used to simulate the situation. The efficacy of natural ventilation as a climate-responsive design approach within environmental planning frameworks was assessed by comparing the outcomes of this scenario with those of the baseline, green roof, and high-performance envelope scenarios (Figure 13).

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Figure 13. Single vs double glazing of the high-performance building envelope

The window-opening control parameters adopted for the natural ventilation scenario are summarized in Table 7.

Table 7. Window-opening control parameters for the natural ventilation scenario

Whenever there were higher external temperatures than the internal ones, high external temperatures, or when cooling systems were being used, the windows would be kept closed. Moreover, when the temperature difference between external and internal temperatures is large enough, the ventilation process during nighttime would take place in order to enhance the process of heat dissipation. Through minimizing unnecessary heat gain, our method ensured that natural ventilation would contribute to thermal comfort.

8.5 S4: Shading devices strategy

In order to assess how well external solar control measures can lower solar heat gains and enhance indoor thermal conditions in buildings situated in hot, dry climates, the Shading Devices Strategy Scenario was created. In this case, fixed and orientation-specific shading devices, such as recessed window shading, vertical fins, and horizontal overhangs, were added to the baseline façade configuration of the Al-Khwarizmi College of Engineering at the University of Baghdad. Limiting the amount of direct solar radiation that strikes glazed and opaque surfaces is the main goal in order to lower cooling loads and enhance occupant thermal comfort.

Energy Plus solar radiation algorithms were used to modify façade-level solar control parameters and define external shading geometries in order to model shading devices in DesignBuilder. In order to maximize shading effectiveness during peak summer solar angles while preserving sufficient daylight access, shading dimensions, projection depths, and spacing were assigned according to window orientation. The dynamic solar position, shading obstruction, and surface heat balance interactions were all taken into consideration in the simulation. Thermal comfort indices (PMV/PPD), indoor operating temperature, solar heat gain through glazing, and annual cooling energy demand were all analyzed to evaluate this scenario's performance. To ascertain the relative contribution of shading devices as a passive cooling strategy within integrated environmental planning, the results were compared to the baseline, green roof, high-performance envelope, and natural ventilation scenarios.

8.6 S5: Landscape and microclimate integration scenario

The purpose of the Landscape and Microclimate Integration Scenario was to assess how vegetated outdoor elements affect the building's immediate microclimate and indirectly affect its thermal performance. In this case, the incorporation of landscape elements like trees, grassy areas, permeable surfaces, and shaded courtyards improved the baseline site conditions of the Al-Khwarizmi College of Engineering at the University of Baghdad. In order to decrease heat gains to the building envelope and improve indoor thermal comfort, the strategy seeks to lower ambient air temperature, limit reflected solar radiation, and enhance outdoor thermal conditions.

In the DesignBuilder software, the effects of the landscape and its microclimate were modeled with modifications to the parameters for the site and external surfaces based on the capacity of the Energy Plus software. These included the modification of the ground surface solar absorptance with the implementation of a vegetated ground cover, the identification of the shaded external surfaces based on the tree canopy components and other external obstructions, and the consideration of the evapotranspiration effects based on the changes to the conditions for the surfaces' heat balance. Though there is a lack of comprehensive simulation for the physiology of the vegetation by the Energy Plus software, there is an option for the indirect consideration of the mitigating effects of the microclimate.

The integrated scenario was simulated using the Energy Plus engine to capture the combined effects of reduced conductive heat transfer, controlled solar gains, enhanced convective heat removal, and microclimate mitigation. The performances that were evaluated include annual and peak cooling energy demand, indoor operative temperature, thermal comfort indices (PMV and adaptive comfort), and carbon dioxide emissions. Results from this scenario have been compared with the baseline and with individual strategy scenarios in order to quantify the added value of integrated green infrastructure within environmental planning and to demonstrate effectiveness in using simulation-driven decision-making for achieving sustainable building performance.

Vegetation impact modeling was done using the DesignBuilder green roof and landscaping properties like shading, evaporative cooling estimation, soil heat storage, and altered surface characteristics, instead of physiological plant modeling. As seen in the image, the sun-path and solar analysis were performed for the Al-Khwarizmi College of Engineering building using DesignBuilder.

The major building elements are denoted by the grey blocks in the image, whereas the exterior shade zones are illustrated with yellow blocks in the diagram. The image shows that solar motion, the positioning of buildings, and the functionality of landscapes in the environment help reduce heat exposure in arid environments.

As transition zones between the building mass and the landscape, the zones in yellow also make an important contribution to the environment. This is because these landscaped zones prevent excessive heat gain through the open façade. In addition, the landscaping contributes to the process of passive cooling through air movement and shading of the ground surfaces. The calculated building and landscape areas and their respective proportions of the total site area are presented in Table 8.

Table 8. Building and landscape areas as percentages of the total site area

The simulation results demonstrate that all investigated green infrastructure scenarios reduced annual cooling energy consumption relative to the Base Case, although the magnitude of improvement varied among the strategies. The high-performance envelope scenario achieved the greatest reduction, confirming the importance of improving the thermal characteristics of the building envelope under Baghdad’s hot-desert climatic conditions. The shading-device and natural-ventilation scenarios also produced noticeable reductions by limiting solar heat gains and improving passive heat dissipation. The green-roof and landscape–microclimate scenarios provided additional benefits, although their individual effects on annual cooling energy consumption were comparatively smaller. These results indicate that an integrated strategy combining envelope improvement, shading, natural ventilation, green roofs, and landscape measures offers greater environmental performance than applying any single intervention independently, as shown in Figures 19 and 20.

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Figure 19. Comparison of energy consumption values for the Base Case and alternative techniques

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Figure 20. Comparison of indoor operative temperature values for Base Case and alternative techniques

Overall, the DesignBuilder-based evaluation verifies that the development scenario saves a significant amount of energy, especially when temperatures are high. These results emphasize how crucial it is to incorporate passive and nature-based solutions early on in the building and urban design process in order to improve energy efficiency, save operating costs, and encourage low-carbon development plans in hot climates.

The five individual passive design approaches (S1-S5), along with an integrated approach (Integrated Scenario), are compared through the simulation model against the conventional Baseline Case. The objective is to optimize the performance of the building through lowering the amount of cooling energy use, carbon emission, and interior thermal comfort parameters (average operative temperature and predicted mean vote).

The simulation results compare the five individual passive-design scenarios and the integrated Development Case based on annual cooling energy consumption and average indoor operative temperature. The Base-Case scenario showed excessive overheating conditions, with the internal temperature being approximately 40.14 ℃ and a maximum cooling load requirement of 56857 kWh. Such results highlight the environmental challenges faced in areas characterized by arid climate conditions, where buildings are greatly affected by solar radiation.

The green roof solution (S1) indicated that there was an improvement in the energy consumption used for cooling purposes by up to 48,490 kWh among all the examined solutions, as well as a reduction in the internal temperatures up to about 26 ℃. The inference from this is that the planting of plants on the roof increases its insulating capabilities.

By comparing the results with the Case S2 scenario, which depicts the High-Performance Building Envelope scenario, it is evident that there is an improvement in terms of thermal performance and energy consumption. As can be seen from the above graph, under the High-Performance Building Envelope Scenario, the indoor temperature average has fallen to approximately 26 ℃, while the cooling energy consumption has decreased to about 47,200 kWh per annum.

The reduction of cooling demand and temperature inside buildings was greatly improved through the use of natural ventilation (S3). The enhancement in cross-ventilation and airflow enabled effective dispersion of heat storage inside the building.

Maintaining interior temperatures within the range of 28 to 29 ℃, the application of shading devices (S4) showed reasonable energy-saving results, decreasing cooling requirement to approximately 50,940 kWh. The problem of solar radiation on the building façade was effectively reduced through exterior shading, particularly in the afternoon.

Finally, the landscaping intervention (S5) contributed the most modest individual energy savings among the five scenarios, with an annual fuel total of approximately 54,500 kWh — a reduction of about 4.1% compared to the baseline. However, its primary value lies in microclimate improvement: by reducing ambient outdoor temperatures through evapotranspiration and shading of surrounding surfaces, S5 amplifies the effectiveness of the other strategies when combined in the integrated Development Case. This synergistic effect explains why the Development Case (45,872 kWh, 19.3% reduction) outperforms any individual scenario. Table 13 summarizes the individual performance results for all five scenarios (S1-S5) alongside the integrated Development Case and the Baseline, enabling a direct comparison of the incremental contribution of each green infrastructure strategy.

Table 13. Summary of individual green infrastructure scenario performance vs. baseline

The findings of the simulation showed a significant decrease in the number of hours of annual discomfort, especially during the peak of the summer season when the risk of overheating typically runs highest. When compared to the base scenario, both the combined scenarios demonstrated significant improvements in adaptive comfort performance, decreased cooling loads, and stable operating temperatures. Such improvements indicate the efficiency of green infrastructure as a quantifiable performance-based design solution as well as an environmental enhancement technique.

Additionally, by objectively evaluating infrastructural techniques, the DesignBuilder simulations confirmed that green infrastructure improves microclimatic efficiency, reduces energy consumption, and minimizes the effects of urban heat islands. The important role of an integrated planning approach has been proven by the findings that the combined use of multiple techniques achieved greater improvement in performance than separate approaches.

The findings highlight the importance of implementing green infrastructure in the beginning stages of construction in order to achieve maximum energy, thermal, and environmental advantages from the viewpoint of environmental development. The study also emphasizes how simulation-based decision-making tools could encourage evidence-based policy advancement and direct sustainable urban development.