The Impact of Green Roofs and Internal Patios on Energy Consumption in a School Building

A computer simulation model

Abstract

Sustainability has attracted expert's attention in recent years, which is generally categorized into social, economic, and environmental approaches. The verification of green roofs’ positive environmental impact has been investigated in several studies. However, little researchers have tested the combined effect of green roofs and internal patios on energy consumption. The purpose of this research studies the energy performance of a scholastic building equipped with a green roof and internal patios since the vast area of schools' roofs has great potential for green roof installation. Moreover, schools can play an underlying role in promoting sustainability as the first culture-creating social environment. For this aim, computer simulations of a school building on the presence and absence of a green roof plus two internal patios were conducted by Design Builder software. As a result, the analysis showed that these living elements as green architectural parameters in designing a green school make a significant reduction rate of energy consumption. The results of these simulations showed a 34.23% decrease in the rate of heat generation, 17.48% in electrical energy for cooling, 15.30% in sensible cooling, 17.46% in total cooling, 34.22% in zone heating, and 21.04% in the scale of the total electrical energy for one year.

Introduction

Until 2008, when the largest proportion of the urban population in the world was specified, more than 50% of the global population lived in the cities. It is expected that the mentioned rate will rise to approximately 70% by 2050 (Pećarević, Danoff-Burg et al., 2010). As a consequence of urban sprawl, abrupt declines in biological diversity(Boesing, Nichols et al., 2018), noise and air pollution increase due to dense population activities and airborne particulates (Peck, Callaghan et al., 1999), the ambient temperature in urban areas because of global warming and heat island effect (Santamouris, 2014), a considerable rise in the rate of human anxiety and depression, health-related quality of life has decreased (Garrido-Cumbrera, Ruiz et al., 2018). Finding practical ways such as the utilization of a green roof or other vegetated living elements to improve this situation in cities toward sustainability in urbanized regions (Peck, Callaghan et al., 1999), is of vital importance. The uniqueness of this research is the investigation of the combination of 2 vegetated living elements, green roofs and internal patios equipped with vegetation, because they have mutual impact of shading by vegetation canopy and their evaporative cooling properties on temperature reduction (Jeong, Ho et al., 2009). These living elements help to stop the local climate change by heatwaves reduction and the climatic conditions improvement (Shafique, Kim et al., 2018). They have also been proposed as having hydrologic and energy-saving benefits (Williams, Lundholm et al., 2014), cooling ability, acting as passive filters of airborne particulates matter (Speak, Rothwell et al., 2012), and courtyards and vegetation enhance both the performance of the courtyard itself and the overall building (Ibrahim, Al Badri et al., 2022) they also enhance human health and well-being (Panagopoulos, Duque et al., 2016). Some studies showed that modifications like a court yard form can increase daylighting levels by 21% and reduced solar radiation exposure by 31% in enclosed corridors (Maksoud, Mushtaha et al., 2022).

Literature Review

Amongst different types of buildings, schools, which their roof ratio to the wall is large, provide great opportunity to be equipped with the living elements technologies. Regardless of their positive social impact, considering psychological and aesthetic values, vegetated roofs can increase energy savings in this type of low-rise buildings with a large roofing area (Vera, Pinto et al., 2017). According to the LEED for Schools, a sustainable educational space or green school should include: 1) sustainable site, 2) indoor environmental quality, 3) water productivity, 4) sustainable energy, 5) sustainable materials and resources, 6) innovation in design, and 7) local priorities. Mohammadi Ghazi Mahalle (2008) has mentioned climatic design principles as the key factors in scholastic design. Alcázar and Chávez (2014) have studied the analysis of the educational programmatic matter for the promulgation of the usage of environmentally friendly architecture in elementary schools. Eventually, it was approved that children are capable of learning the bio-climatic and sustainability concepts beside their usual lessons; therefore, with using the main source for educational plans and training of the bio-climatic parameters in a simple scholastic way, we can achieve to the creation of green knowledge for new generations. Majedi and Siyadati (2015) noted that today, the determination to develop green roofs enhances the sense of creativity in educational spaces and environmental improvement. Although there are various barriers for promoting green roofs, Zhang et al. suppose that a practical way of adopting extensive green roofs is in buildings like schools, which are low-rise, easily accessible for people, and have a vast unused area of the roof (Zhang, Shen et al., 2012).

Peck, Callaghan et al. (1999) believe that promoting green technological systems on the roof of buildings with different functions help human to achieve sustainability. Santamouris, Pavlou et al. (2007) studied the energy performance of a green roof system installed on a kindergarten. The final results showed total cooling load reduction ranged from 6% to 49%, however this rate changed from 12% to 87% for the top floor under the roof. They mentioned that the green roof system positively affects the heating load and is a major advantage gained by the green roof although systems that are usually used in order to reduce cooling load, increase of its heating load. Tang, Zheng et al. (2010) made research for evaluating the impact of energy consumption and thermal parameters in summer on roofs and compare the green and bare roof’s performance in the air-conditioned and natural indoor environment. It was indicated the heat flow of the green roof decreased by about 70%. Additional equivalent thermal resistance by the roof equipped with green roof was about 1.0 m²·K/W in the air-conditioned and its cooling efficiency was about 111% in the natural condition. Gagliano, Detommaso et al. (2015) examined the energy performance of three roof types, resulting that green roofs provide higher energy savings and environmental benefits, chiefly insulated green roofs rather than highly insulated standard roofs. Refahi and Talkhabi (2015) studied 3 climate zones in Iran to analyze the rate of energy saving, reached by green roof installation, and demonstrated that the level of energy saving went up around 8.5% in very hot dry, 9.2% in warm dry, and 6.6% in mixed dry climate. However, Bevilacqua, Bruno et al. (2020), considering their experimental condition, concluded that in reduction of the cooling energy, non-insulated green roofs provide best results, with annual savings of over 34.7% of cooling energy. In details, 43.8% for cooling energy demand for the last floor, and 28.2% for heating energy. They indicated that the indoor thermal comfort improvement in both winter and summer is achievable as a result of green roof usage (Bevilacqua, Bruno et al., 2020).

Green roofs have a significant influence on buildings’ energy demand. Overall, the rate of thermal flux is reduced as a result of evaporation, insulation, and thermal mass increase, and because of roofs being shaded by the set of layers during the warm weather (Oberndorfer, Lundholm et al., 2007). In the 2002 summer, research was conducted at Pennsylvania State University, and showed that irrigation and water surface evaporation would be the most influential contributor to decrease building energy demand for cooling on the last floor under green roofs (Oberndorfer, Lundholm et al., 2007). A study in Japan, in 2001, showed a 50% decrease in the rate of heat flux in a building per year (Onmura, Matsumoto et al., 2001). In Singapore, in 2003, research results showed a 10% decrease in the proportion of heat transfer of a roof, when a green roof is installed rather than a typical roof (Wong, Chen et al., 2003). A research on a residential 8-story building in Madrid, Spain demonstrated a 6% decrease in the cooling loads. The cooling load decreased by 10% for the entire building in the case of peak demand. For the four floors under the green roof, this rate was 25%, 9%, 2%, and 1% respectively (Saiz, Kennedy et al., 2006). In Toronto, Canada, in 2006, the cooling load of a residential house decreased 25% in July and for the top floor under the green roof, this rate was 60% (Saiz, Kennedy et al., 2006). Moody and Sailor (2013) ran simulation modeling in 4 USA cities to test the monthly and yearly energy demand, when a green roof is added to a structure. This resulted in a reduction of required heating energy in winter, improved thermal performance for cooling energy in summer, and for spring and fall, cooler inside surface of the green roof rather than a conventional one (Moody and Sailor, 2013). Ascione, Bianco et al. (2013) investigated on the effectiveness of green roofs in the Europe climate. It showed that in European cooler climates, energy demand reduced between 1-11%, and for warmer climates it changed between 1% to 7%. Vera, Pinto et al. (2017) did research on the impact of an extensive green roof’s layers, installed on retail stores, and its thermal performance in Semiarid cool climates and marine climates in 3 cities. As a result, the effectiveness of green roof over insulation on cooling load reduction was approved and the main causes were evapotranspiration and shading effect. Although insulation cannot be superseded by a green roof to reduce heating loads, they can decrease the vegetated roof’s ability for the purpose of cooling loads reduction (Vera, Pinto et al., 2017). Furthermore, the investigation done by Hussien, Jannat et al. (2023) illustrated notable reductions in both electricity and gas consumption across various cities in England. Liverpool achieved a substantial electricity saving of 13,233.4 kWh, alongside a gas saving of 2,540.6 kWh. In Sheffield, the electricity savings totaled 4,291.9 kWh, with gas savings reaching 824 kWh. Manchester reported significant reductions with 16,094.7 kWh saved in electricity and 3,089.9 kWh in gas. Oldham also saw considerable savings, with electricity consumption reduced by 15,057.5 kWh and gas by 1,963.8 kWh. Doncaster demonstrated the most impressive figures, saving 58,906.6 kWh of electricity and 11,309.1 kWh of gas. These results collectively underscore the effectiveness of energy-saving measures implemented across these cities(Hussien, Jannat et al., 2023). Another study on optimization of daylight and solar radiation exposure by Maksoud, Mushtaha et al. (2022) showed the design modifications contributed to a 15% reduction in cooling energy consumption due to improved thermal performance, which shed light on the importance of implementing the mentioned methods. Please see the summary of the similar studies on the table below.

Contemporary green roofs, which are equipped with plants, have ancient roots. The first green roofs in the world are considered to be the hanging gardens of Semiramis known as Syria (Oberndorfer, Lundholm et al., 2007). Contemporary ones are "engineered ecosystems (Wolf and Lundholm, 2008) " and include plants, waterproofing membrane, root barrier, and drainage layers. The top greenery layer provides stability to the substrates and visual relief (Oberndorfer, Lundholm et al., 2007), decreases the roof surface temperature, vent the stormwater from the roof via transpiration and create positive effects on urban flora and fauna, as these areas operate as natural environment for native biodiversity (Madre, Vergnes et al., 2014), and seems invulnerable habitat for birds and insect. Green roofs improve air quality and help moderate the negative consequences of air pollution and noise pollution (Van Renterghem and Botteldooren, 2009), especially in the urban environment (Rowe, 2011) with nitrous oxides and volatile organic compounds reduction by plants (Peck, Callaghan et al., 1999). They also contribute to the mitigate the heat island effect in cities and help to accomplish a decline in the level of greenhouse gas emissions and negative impact of climate change via energy conservation.

Internal patios are usually known as small scale court-yards, which have about 5000 years of history. Normally, they are open air spaces (Taleghani, Tenpierik et al., 2014) surrounded by building and usually located different type of vegetation, consequently can positively and considerably impacts the thermal energy in urban areas (Richards, Fung et al., 2020). Patios are semi-controlled environments, which has great potential for energy saving, specifically for heating, (Pitts and Saleh, 2007) and for providing efficient microclimates (Soflaei, Shokouhian et al., 2020). They improve the level of energy efficiency especially in low-rise buildings (Aldawoud and Clark, 2008) since they are transitional spaces between outdoor and indoor air and light (Chun, Kwok et al., 2004). Applying internal patios in building design help to improve moderation in natural extremes, and at the same time, they are central accessible spaces for socializing(Reynolds, 2002). They affect the environment by reducing the temperature as a source of evaporative cooling (Cadima, 1998). From the first researches, it was proved that different factors affect the courtyard’s microclimate, such as material, wall thickness, aspect ratio, wind direction, and openings(Hall, Walker et al., 1999). In 2007,Research on the influence of an internal patio in a building in the hot-dry and hot-humid climates, showed a positive result on the energy performance in the mentioned climates, and height of glazing part and glazing percentage of a surrounded courtyard by glass on all four sides are indicated as the key factors (Aldawoud and Clark, 2008). Furthermore, in 2015, the volume to wall area ratio of internal patios has been considered as a significant factor in the rate of heating and cooling loads as a result of received solar radiation and shading (Manioğlu and Oral, 2015). In 2019, a parametric analysis of courtyards’ influence, showed that courtyard geometry is a highly influential parameter to decrease the rate of cooling load (Forouzandeh, 2019) . Another research in 2018, demonstrated that the thermal and microclimatic function of courtyards is directly affected by the length/height ratio significantly (Zamani, Heidari et al., 2018).

In 2012, a two-phase investigation was carried out in Dubai, the United Arab Emirates, to compare the energy performance of a simulated building when a courtyard is added and the influence of the number of floors, type of glazing, wall thickness and insulation type and thickness as variables on the courtyard’s performance. It indicated a 11.16% increase in the rate of annual energy saving, and more useable daylight in both cold and hot days of the year(Al-Masri and Abu-Hijleh, 2012). In 2019, research on the indoor energy consumption and on the indoor comfort zone of a building, equipped with internal courtyard, showed that in the longest day of a year, the courtyard is 1.2 °C cooler than the outdoor space. And the rate of fluctuation is less than exterior environment. Therefore, the efficiency of courtyarda as a passive strategy caused by shading walls, cooler microclimate of the internal patio in the day-time and warmer in the night-time was proved(Zamani, Heidari et al., 2019) . In 2019, a study on the shading performance of traditional courtyard houses in the hot and cold climates of Iran showed that the best form for a courtyard in these climates is rectangular. The results indicated that increasing the ratio of length and the height of surrounded walls to width raises the percentage of shading (Teshnehdel, Bahari et al., 2019). In 2018, a study on the impact of courtyard design on the building energy performance in china showed a 19.6% of cooling load in a hot summer and 22.3% of heating load in a cold winter(Xu, Luo et al., 2018). The sustainability of urban planning in arid regions has been a subject of extensive research. Mohamed, Paleologos et al. (2018) explore the viability of garden cities in desert environments, highlighting the challenges and potential solutions for sustainable development in such harsh climates. Similarly, Respati and Pindo (2013) discuss the green city design approach as a proactive measure against global warming, emphasizing the importance of integrating green spaces into urban planning to mitigate environmental impacts. Further, Sangwan, Kumar et al. (2023) examine the amorphous nature of green spaces in Indian urban planning, providing insights into the complexities and benefits of incorporating green areas in densely populated urban settings.

In a determined geographical location of Iran, this research studies the energy performance of a modeled scholastic building before and after covering with a green roof and being equipped with internal patios including green vegetation. On this aim, as the technical green roof systems are many and various, a literature review of green roof systems is conducted, then the research methodology is presented. Eventually, computer simulations via DesignBuilder, an EnergyPlus-based software was used to survey the enhancement of building thermal and environmental performance impacted by those living green equipments.

Green roof systems are defined in two basic groups (Table 1) as extensive and intensive.

Table 1. Fundamental differences of extensive and intensive green roofs (Oberndorfer, Lundholm et al., 2007)

Type	Extensive	Intensive
Main Objectives	Environmental functions such as energy conservation, aesthetically pleasing environment and storm-water management	Environmental functions such as energy conservation, aesthetically pleasing environment, increased useful space and storm-water management
Cost	Relatively lower cost	Higher cost
Structural design specifications	Generally standard structural design specifications; additional 70- 170 kg/m2	Essential structural improvements in design phase; additional 290- 970 kg/m2
Substrate weight	Light	Light to heavy
Substrate porosity	High	High
Soil height	2 ≤ h ≤ 20 cm	20 cm ≤ h
Vegetation	species with low speed growth, shallow root plants, limited plant species	Any type of plant including trees and shrubs
Irrigation and maintenance	Bare necessity	Highly required
Accessibility	Generally inaccessible except for the purpose of maintenance	Generally accessible; bylaw considerations

It can be stated that extensive green roofs are lower in price and lighter in comparison with intensive green roofs and require less protection. Although low vegetation is suitable for extensive green roofs, intensive one support shrubs and trees. (Karachaliou, Santamouris et al., 2016). Both types are divided into accessible green roofs or inaccessible green roofs. The first category is usually in a flat form and can be used by individuals as roof gardens. However, inaccessible roofs do not support this way of utilization, and just periodic maintenance is done by limitations (Peck, Callaghan et al., 1999).

Diverse green roof systems for climatic condition are supplied for customers. According to Bianchini and Hewage (Bianchini and Hewage, 2012). These systems generally include: 1) A root barrier: the lowest level of layers on the buildings’ roofing installed to provide a waterproofing membrane for protection against leak and plant’s roots, 2) Drainage layer: an empty layer amongst other installed layers to let the surplus water to exit without any limitation. It minimizes the danger of water leaks on the building’s roofing and protects the root barrier to be damaged by the gathered water in the membrane, 3) Filter: a layer to prevent blocking the drainage layer by passing the water clearly, while preserving the entirety of vegetation and the growing medium, 4) Water retention layer: consists of mineral wool and polymeric fibers, and is mounted above the filter to be 1.0 cm - 6.5 cm deep, 5) Growing medium and vegetation(Bianchini and Hewage, 2012), According to local climatic condition and form of urbanization, indigenous materials and plants play leading role for achieving a successful green roof (Vijayaraghavan, 2016). If the optimum use of diverse plant species is possible, unnecessary waste of water will decrease, and roof surface can be cooled more efficiently (Wolf and Lundholm, 2008). The building ceiling must be covered with an insulator layer such as bitumen for water proofing or any other waterproof coating. It is carpeted by the mosaic or asphalt or cobble stone. Efficient garden irrigation system is needed and each of them should be installed in its place carefully(Razavian, Ghafouri et al., 2011). Extensive green roofs are divided to three categories (Baciu, Lupu et al., 2019). Based on executive systems, average depth of cultivation layer and the scales of the essential installations, they are: (a) Complete or Widespread system (Figure 1.A): each piece is installed as a layer of the roof. (b) Modular system or plant box (Figure 1.B): vegetation trays are placed on the built roof, and (c) Precultivated vegetation blankets (Figure 1.C): all the layers were rolled and are opened on a constructed roof (Oberndorfer, Lundholm et al., 2007). Intensive green roof includes deeper soil (Figure 1.D) that allows roofs to accommodate larger plants. Intensive green roofs support heavier loads; thereby, there is no weight problem and the drainage layer could be simpler (Bianchini and Hewage, 2012). Usually, the drainage layer is a mixture of round pebbles and filter, and there is no limitation for thicknesses over 4 cm (Bianchini and Hewage, 2012).

Figure 1. Extensive green roof technology: A) Complete systems or widespread system: B) Modular system or plant box C) Precultivated vegetation blankets (D) Intensive green roof technology

Green roof reduces heat island and provides comfort zone for occupants with regards to temperature and causes energy consumption reduction in buildings (Saadatian, Sopian et al., 2013). According to Peck, environmental building owners benefit economically because increased insulation save the budget needed to cover the cost of; energy consumption. Green roofs reduce the amount of heat flux during warm weather (Oberndorfer, Lundholm et al., 2007), and thereby, increase the rate of thermal insulation. This result in a reduction in the cooling load of building (Del Barrio, 1998; Theodosiou, 2003).

This paper focuses on developing technical information to evaluate the environmental benefits of a green-roofed scholastic buildings with internal patios and their impact on energy demand. The computer-generated simulation provided a method to create virtual environment for evaluation and investigation of energy demand rate.

Research Methodology

In this research, a quantitative method is used to compare the outcomes of simulations of a scholastic building (Figure 2. A) under 2 scenarios. The energy performance of the building on the absence and presence of an accessible green roof plus an internal patio has been examined during a year. Here, the case study is a 2-floor scholastic building with a roof surface area of 1320 square meters and the roof ratio to the exterior walls is 1.06. The simulated building (of the first scenario) is shown in Figure 2.

Figure 2. A) Conventional building plan, B) Building plan equipped with green roof and internal patios, C) 3D of the simulated scholastic building

The building is studied via modeling it in the geographical coordination of 33˚ 55ʹ 05ʺ.93 N, 48˚ 44ʹ 43ʺ.42 E via DesignBuilder software, version 4.7.0.027. The DesignBuilder software, which is as an EnergyPlus-based software tool for estimating energy, carbon, lighting and comfort measurement and control, has been used. Its advantage over other energy software for doing this research is visual modeling creation. This method provides possibilities to model any kinds of buildings in different climatic conditions to assess the environmental harmony. DesignBuilder is a high-tech software to simulate buildings and helps to evaluate the performance of buildings with regards to sustainability factors, which reduce modelling time and increase productivity by assessing integral factors.

It is designed in Borujerd, Iran, the city which has a cold climate (Hedayatian and GOUDARZI, 2016), with an average annual temperature of 17.17 ° C and Annual rainfall of 7.405 mm, and relative humidity of 7.41%(Jahangir, Norozi et al., 2018). To guarantee the maximum energy saving in the specific climatic area the simulation is designed under national building regulations of Iran on energy savings, published in 2010. For Materials, activity, lighting, opening tab, and set temperatures, the general database of the software is used.

In the first scenario, the conventional roof is made up of a 30 cm reinforced concrete layer and 5 cm asphalt. In the second scenario, an extensive green roof with the soil depth of 20 cm and Sedum tall plant species is installed on the conventional roof plus two roofless internal patios with glazing walls, and with the height of 8.7 meters, similar to building height were added. The glazing walls details of each patio, based on national building regulations of Iran is presented in Table 2.

Table 2. Glazing wall details of each Patio

Area of each patio (m2)	Volume/external wall area ratio	Thickness [mm]	Density [kg/m3]	Thermal conductivity (W/m K)
58.7	1.8	25 mm (insulating glass)	2700	1.1

Comparing the outcomes of simulations during a year, the below aspects were figured out:

•    Energy consumption for heating and cooling
•    Sensible cooling
•    Total cooling
•    Zone heating
•    The scale of disposable electricity
•    Monthly energy consumption

The followed steps are presented in the Figure 3.

Figure 3. Simulation Steps

Results

In the first step, the scholastic building is simulated with a conventional roof and no internal patio. Input analysis via DesignBuilder software simulation is conducted and energy consumption output during a year is presented in Figure 4. A. Table 3 presents how energy consumption (electricity) rate decreased for the purpose of heat generation and chilling the internal space to achieve the comfort zone for the second scenario. Here, GR is defined as Green Roof and IP as Internal Patio.

Figure 4. A) Energy consumption rate of the scholastic building with a conventional design, B) Energy consumption rate of the school building when equipped with GR and IP

In the second step, the same scholastic building was simulated to analyze the building's electricity consumption during a year, when a green roof is installed and the building is equipped with the internal patios. (Figure 4 B) the outcomes were compared in Table 3. According to the DesignBuilder software outcomes, the electricity consumption rate for heat generation is 198.70 (MWh) for the building with a conventional design in Fig. 4. A. This rate is 130.68 (MWh) for the building with GR and IP in Fig. 4. B, which shows that 68.02 (MWh) has been saved. The scale of electricity consumption for chilling the conventional building is 158.93 (MWh) (Figure 4. A). It is apparent that this rate for the building with GR and IP (Figure 4. B) achieved to 131.14 (MWh) and according to the Design-Builder outputs, it means that 27.79 (MWh) has been saved.

Table 3. Comparison of electricity consumption rate

Energy consumption/ Building Type		Conventional model	Equipped with GR and PI
System Misc (MWh)		97.77	97.77
Heat Generation (Electricity) (MWh)		198.7	130.68
Chiller (Electricity) (MWh)		158.93	131.14

Figure 5 A, during a year, shows the amount of heat energy that must be removed from the building to maintain the indoor design temperature and the zone heating. The scale of sensible cooling is -298.70 (MWh) in the conventional state. This rate has achieved to -252.94 (MWh) for the building with GR and IP (Figure 5 B), which has saved 45.76 (MWh) in the energy consumption according to the DesignBuilder software outputs. The total cooling load in the Figure 5. A is -254.29 (MWh) in the normal state, which has been achieved to -209.83 (MWh) when a GR and IP is added (Figure 5 B), resulting in 44.46 (MWh) decrease in the rate of energy consumption. The zone heating in this scholastic building is 278.18 (MWh) in the conventional state (Figure 5 A), that is in the presence of GR and IP 182.96 (MWh), presented in Figure 5 B. Eventually, 95.22 (MWh) has been saved in the scale of energy consumption. Table 4 represents the comparison of two conditions.

Figure 5. A) Sensible, total Cooling, and zone heating rate of the scholastic building with a conventional design, B) Sensible, total Cooling, and zone heating rate of the school building with GR and IP

Table 4. Comparison of Sensible, total Cooling, and zone heating rate

Fuel consumption/ Building Type		Conventional model	Equipped with GR and PI
Sensible Cooling (MWh)		-298.7	252.94
Total Cooling (MWh)		-254.29	-209.83
Zone Heating		278.18	182.96

In Figure 6 A, according to the DesignBuilder numeric outputs, the scale of total electric energy consumption of the building is 455.41 (MWh) during one year in the conventional state. This scale has achieved to 359.60 (MWh) (Figure 6 B) when a Gr and IP is added, resulted in saving 95.81 (MWh) in the rate of disposable electricity.

Figure 6. A) Total Electricity consumption rate during a year in the conventional state, B) Total Electricity consumption rate during a year when equipped with a GR and IP.

Table 5. Comparison of total electricity consumption rate

Energy consumption/ Building Type		Conventional model	Equipped with GR and PI
Electricity		455.41	359.6

According to the DesignBuilder results, the whole building energy demand in all months of a year is presented as line graphs in Figure 7: the conventional building state (Figure 7 A), and when equipped with a GR and IP (Figure 7. B).

Figure 7. A) Monthly Energy load during a year in the conventional stateB) Monthly Energy load when equipped with GR and IPM

In detail, the rate of the energy demand of two scenarios, without and with GR and IP, is presented in Figure 8 respectively. In this part, the cooling sensible load, and the total cooling load are considered for months, in which the outdoor temperature is equal to or higher than design data. On the contrary, the heating generation is considered for the months, in which the outdoor temperature is equal to or lower than design data.

Figure 8. The monthly rate of energy demand of two scenarios

Figure 9. The energy consumption variations in kWh/m2 and in %, for the whole building

Based on the above tables, it is clear that, in the warmer months of the year which are the cooling period, from April to September, the rate of monthly sensible cooling load showed a significant decline as a result of the combined effect of green roof installation and adding internal patios to the building. This rate indicated a 5% decrease in April and reached a maximum of 23% decrease in June. Similarly, the monthly total cooling showed a 6% decrease as the minimum efficacy, and a maximum of 24% decrease in the mentioned months.

The combined effect of the mentioned green living elements on the zone heating was significant. As can be seen, the green elements caused the zone heating rate to decrease by 79% for the first month of autumn (September), and the minimum variation was 29% in April. This rate for a year period is presented below in summary (Table 6).

Table 6. The comparison of DesignBuilder outcomes summary for the two scenarios

Energy consumption rate during a year	conventional building (MWh)	Building equipped with a green roof & internal patios (MWh)	Saving scale (MWh)	Variation (%)
Heat generation (electricity)	198.7	130.68	68.02	-34.23%
Chiller (electricity)	158.93	131.14	27.79	-17.48%
Sensible cooling	-298.7	-252.94	45.76	-15.30%
Total cooling	-254.29	-209.83	44.41	-17.46%
Zone heating	278.18	182.96	95.22	-34.22%
Total electricity	455.41	359.6	95.81	-21.04%

Conclusion

In the present research, the analysis and calculation of the combined effect of installing a green roof and 2 internal patios, directly connected to the building, were investigated with regard to the energy consumption rate for the whole scholastic building, located in the cold climate of Iran. Because, both green roof technology and internal patio are considered as sustainable architectural elements and they play a fundamental role from an economic, social, and environmental point of view. Comparing the rate of monthly energy consumption in the two scenarios indicates energy-saving between 5%-23% for the sensible cooling load, 6%-24% for total cooling load, and 29%-79% for the heating load. According to the Design Builder software analysis, the biggest variation of energy consumption was a decrease of 34.23% for the heat generation rate. However, the smallest percentage of variation was for sensible cooling of 15.30%.

The results of this research agree with previous separate investigations in the literature review over the effect of a green roof installation on building and the thermal influence of internal patios on the indoor condition. It should be noted that, a combination of green roofs and internal patios can be considered as sustainable design strategies in designing, specifically scholastic buildings because of their mentioned geometry in the text and their social and educational role. Importantly, it can be concluded that, the combination of these two sustainable design strategies in the cold climate of Borujerd demonstrated more efficacy rather than an adaption of each strategy individually as no previous studies indicated energy consumption variation as high as 21.04%.

This research accentuates how beneficial is the combination use of sustainable design technologies, specifically green living elements is, and why these technologies promotion and development are crucial. The result of this study encourages experts and stakeholders in the construction sector, to take green living elements implementation seriously in urban areas since the economic and environmental benefits were proved as energy-saving during cooling and heating periods.

Author Contributions

Conceptualization, N.N. and H.N. methodology, N.N. and H.N. software, N.N. and S.B., investigation, S.B., N.N., K.T. resources, A.B. and L.B. data curation, N.N., writing—original draft preparation, S.B. and N.N. writing—review and editing, S.B., supervision, H.N., L.B., K.T., and A.B. 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.

Acknowledgments

Financial support of these studies from Gdańsk University of Technology by the DEC- 1/1/2023/IDUB/I3b/Ag grant under the ARGENTUM - 'Excellence Initiative - Research University' program is gratefully acknowledged.

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