Dynamic vertical green walls & shading systems integration to enhance energy efficiency & thermal comfort: A case of educational building skin retrofit in a Mediterranean city

Background

Buildings account around 30 to 40% of global energy use. Not considering Egypt’s unique building context, geography, and climate results in ineffective building performance. Occupants’ needs, particularly in terms of health and productivity, are often overlooked.^9,10 The main energy needs of schools are mainly related to illumination and airflow. Since the skin of the building serve as the division between inside and outside areas, properly managing natural light and airflow is essential for sustainable design strategies that improve indoor environmental quality (IEQ), comfort, health, and productivity. With the advancement and economic growth in Egypt, there has been a move towards the Western style of fully glazed building facades, ignoring the local environmental and cultural factors.¹¹ This pattern has led to a rise in energy consumption, worsened by energy deficits, and has added to economic difficulties. In reaction, Egypt has encouraged stakeholders to adopt modern technologies designed to decrease energy usage.¹² The purpose of this paper is to illustrate the advantages of dynamic glass ventilation systems (DGVS) in educational facilities by comparing building performance with and without DGVS under specific local environmental and climatic conditions.¹³

Climate change impact on Alexandria

Coastal urban areas are facing increased vulnerability to the consequences of climate change, including instances of flooding, rising sea levels, and severe climate conditions due to their geographic location.¹⁴ These events disrupt infrastructure, construction, transportation, waste management, and communication networks, affecting both cities and their populations.^15,16 With over 360 million people living in coastal regions less than 10 meters above sea level at risk from natural disasters exacerbated by climate change, cities like Alexandria in Egypt are already experiencing climate challenges. Alexandria’s population of 5,449,817 is growing at 1.9% annually and has seen changes in temperature and precipitation with having a mean yearly temperature of 20.8 °C and 181 mm of rainfall.¹⁷

Special aspects that affect educational building’s behavior

In educational buildings, occupant comfort is essential for creating an optimal learning environment. Four key factors influence this comfort: Indoor Environmental Quality (IEQ), thermal comfort and visual comfort, IEQ focuses on the air quality, ventilation, and the presence of pollutants, directly affecting the health and cognitive function of occupants.^18,19 Thermal comfort relates to maintaining appropriate temperature and humidity levels to ensure a pleasant and productive atmosphere. Visual comfort, on the other hand, involves proper lighting conditions and natural daylight, which reduces visual fatigue and enhances concentration. These factors collectively shape the overall experience of those within educational spaces, promoting both well-being and academic performance.²⁰

Building performance: IEQ in educational buildings

In educational buildings, the integration of energy efficiency with occupant well-being is critical. The comfort and satisfaction of students and staff are influenced by both the physical attributes of the space and their perceptual experience.²¹ Indoor Environmental Quality (IEQ) plays a central role in this, impacting on the overall quality of life and learning environment.²² Key components of IEQ in educational settings include air quality, thermal comfort, visual comfort, and acoustic comfort. While all these elements are crucial, this discussion will focus on thermal comfort and its relation to energy use, which directly affects both well-being and operational efficiency in educational buildings.³

Thermal comfort in educational buildings

Thermal comfort is a key factor in ensuring a positive learning environment in educational buildings. When students and staff feel thermally comfortable, their ability to focus and perform improves. Various individual and environmental factors contribute to thermal comfort, including personal factors like metabolic rate and clothing choices, and environmental factors such as temperature, humidity, air velocity, and solar radiation.²³ Inadequate thermal comfort can lead to higher energy consumption as buildings strive to achieve a comfortable indoor climate.²⁴ Therefore, addressing thermal comfort during the design phase of educational buildings is essential to ensure both comfort and energy efficiency, ultimately reducing operational costs and promoting a sustainable learning environment.²⁵

Visual comfort in educational buildings

In educational spaces, visual comfort is fundamental to both student well-being and academic performance. Lighting—both natural and artificially influences how well occupants can see and focus. Poor lighting can hinder reading, learning, and overall health.^26,27 The design of windows to maximize natural light while preventing excessive glare, and the careful selection of artificial lighting, are key considerations for creating a comfortable and effective learning space.^28,29 Ensuring adequate lighting levels throughout the day is essential to avoid visual discomfort, with a particular focus on controlling glare, which can disrupt concentration and cause visual strain. By prioritizing visual comfort in the design, educational buildings can support student productivity, health, and overall satisfaction. However, excessive natural light can cause glare, which presents visual challenges, with an acceptable glare range of 500-1500 cd/m².³⁰

Dynamic green vertical living walls system (DGVS): overview

Motorized panels can adopt various forms and mechanisms for diverse purposes while supporting plant growth. A suggested classification centers on movement through the wall framework for outdoor and possible indoor uses.³¹ Different versions of this classification are described and demonstrated in three arrangements.³²

1.1 The Hinged Green Window Wall:

Screens installed on windows can pivot inward, enabling the cultivation of herbs and greens on the outward wall, which can be rotated for harvesting or maintenance.³ This design benefits a tall residential building residents who have restricted gardening opportunities. The same concept was displayed at the USA Pavilion at Expo Milano. showcasing a vertical farming system with a movable hinge.³³

1.2 The Sliding Balcony Door Green Wall:

Sliding boards, placed in adjacent overhangs, promote food crops, ornamental plants, and beneficial native species for insects and birds. They can be slid for maintenance and harvest. Mounted on tracks, they block solar radiation, cooling indoor spaces. Boards with ventilation openings pre-cool incoming air, acting as a passive air conditioning system during hot days.²⁶

1.3 Folding Green Brise-Soleil:

Living boards can be combined with brise-soleils, which Shading devices are used to prevent direct sunlight from entering windows or glass doors. This involves folding articulated arms for access to the growing surface through an open window or small overhang. The Pivoted Green Window Divider,³³ oriented vertically, prevents unwanted sunlight, and these devices may also be solar powered.²⁶

Materials

The Living Wall shading devices, implemented in 2012 at the University of Washington in Seattle, created by the UW Green Futures Research team Design and Innovation Laboratory in collaboration with others.³ This green mobile partition aimed to serve as a research case study to understand living wall design parameters and their potential contributions to biodiversity, urban heat island mitigation, building performance enhancement, and water collection.³⁴ The design included two sliding green wall panels, each 10 feet by 10 feet, along with suitable vegetation, a water collection system, and integrated lighting. The green wall connects with architectural elements like Corten panels, extending vegetation up the building’s facade. Documentation of the design, construction, and maintenance occurred over four years (2011-2015) through videos, photographs, and field observations, aligning with the established frameworks for a dynamic shading system.³⁵

Benefits

The Dynamic Green Vertical Living Walls system can adjust to variations in weather and integrating natural light, shade, and air flow, as indicated in Table 1. This aids in decreasing energy consumption in building activities. The exterior design of the framework significantly influences appearance. It has the potential to inspire architects and designers to create excellent performance building facades that involve clients and parties involved by enabling them to utilize diverse technologies and materials for different aesthetic effects.²⁴

Examples analysis

The incorporation of vertical green wall facades has become a prominent feature in modern architectural design, enhancing both aesthetic appeal and environmental sustainability. Three notable examples of such designs include St. Mark’s Apartments, the USA Pavilion at Expo 2015 in Milan, Italy, and the Shang Kai Steel’s SKA building. Each of these projects utilizes green walls to address various environmental and design challenges while promoting energy efficiency and improving urban experience. The green facades not only contribute to the aesthetic and visual identity of each building but also provide functional benefits, such as improved air quality, natural insulation, and noise reduction. By integrating nature into urban environments, these buildings exemplify how vertical greenery can play a vital role in creating more sustainable and livable spaces.

Criteria of the selected examples:

Examples summary:

This table ( Table 2) provides a summarized comparison of the three examples that display the types of green walls, the plant species utilized, the implementation of shading systems, and the assessment of their effectiveness on the buildings.

Conclusion

In summary, dynamic vertical green walls consist of several essential elements, such as structural support frameworks, irrigation mechanisms, plant choices, and monitoring technologies, all collaborating to form a living, flexible system. These factors are essential for maintaining the green wall’s vitality, durability, and efficiency. As cities expand, the incorporation of vibrant green walls will be more vital, meeting environmental and aesthetic demands while fostering sustainability. Effective execution demands meticulous planning, suitable resources, and ongoing research to enhance performance. As shown in the following Figure 1.

Figure 1. Conclusions illustrate the dynamic vertical green walls components, their Functional characteristics, and ecological needs.

Source: modified by Researchers from the original source: (Perini et al. 2011)

Case study selection criteria: AAST Al Alamein campus’s main building

Phase one: Preliminary research

The initial phase of the method includes recognizing the difficulties encountered by the current layout of the analyzed

AAST Al-Alamein campus structure because of climate change. This process is divided into three sections as outlined below:

Issue identification: current structure simulation

On an urban level, the latest update from the UN World Urbanization Prospects shows that cities designed for compact living face extremely high temperatures and challenging weather conditions year-round, especially in summer, which affects the comfort of city residents. At the building level, the main issue for educational buildings is overheating due to direct sunlight, leading to excessively warm indoor spaces. Additionally, the campus experiences noise pollution from the surrounding urban area and high traffic on Sadat’s main road.

To mitigate the local micro-climate and lower influences such as the occurrence of urban heat islands, carbon output, reflectivity, and concentrations of greenhouse gases, the following actions are implemented:

Indoor temperature satisfaction

This element requires information such as the outdoor temperature, wind velocity, and average radiant temperature. The weather in El Alamein is primarily affected by its desert environment and its location near the Mediterranean Sea, which can slightly moderate temperatures, particularly during winter. As shown in Table 3 – Source: Researchers.

Energy usage

The outcomes of this element comprise a data tree that contains all the energy balance factors for the entire building, The normalized energy balance is chosen since the standardized figures enable a comparison of energy consumption results.

Solution identification: material selection

The Energetic Green Vertical Wall System (DGVS) is presented as a solution for optimizing indoor environmental quality (IEQ) and minimizing energy usage. This system is a hybrid that combines green vertical walls with louvers. Various types of sustainable systems exist, each with its distinct set of characteristics, which are:

Determining the solution: movement choice

The adjustment of the building envelope is an additional component that is influenced by a variety of factors including:

These elements are included in the tool for decision support that helps identify the best placement of the building envelope.

Phase two: DGVS design suggestion

The implementation of green walls in the case study of Alamein’s AASTMT. A design-builder utilizing a plugin from the Energy Plus program has been engaged to model the suggested conceptual kinetic green wall, which could be implemented on the campus to meet the previously stated goals (Researcher).

Proposed DGVS design

kinetic green wall louver components and installation

Every green wall includes modular planter boxes that contain pre-planted vegetation. Made from Acrylonitrile-butadiene-styrene plastic, these containers are lightweight and corrosion-resistant. The design guarantees sufficient depth for root structures, fostering robust plant development while allowing ample space in every direction for plants to thrive as anticipated. The boxes are constructed with semi-cylindrical panels that include two rectangular hooks on the rear for straightforward installation. Each modular planter includes two side openings that allow irrigation pipes to run horizontally. The root area of every row, plus two lower openings that aid the movement of surplus water to the appropriate lower planter boxes.⁴⁶ The size of each module measures 0.75 m in width × 0.60 m in height × 0.30 m. deep (See Figure 3). Once the plants reach maturity, the mass. The system’s weight is roughly 160 kg/m².⁵ A waterproof coating composed of rubber and bitumen is meticulously applied and affixed to the existing walls are equipped with anchors to safeguard the building’s envelope from excessive moisture and surface degradation. Metal “C” channels are attached to the walls, and a grid of stainless-steel wire rope is attached to the louvers on the net plate to facilitate kinetic movement in reaction to sunlight (Researcher).

Figure 3. Modular planter box.

Source: Researchers.

Proposed building simulation

Recreations assess the comfort of indoor warmth, the presence of sunlight, and the energy usage of the building with the suggested DGVS plan; to measure the effectiveness of DGVSs (see Figure 4) (Researcher).

Figure 4. implementation of kinetic green wall louvres in different facades of Alamein campus of AAST (plan).

Source: Researchers.

Comparison: current versus suggested

Assessing the existing design results in relation to the expected performance of the building concerning indoor thermal comfort, daylight, and energy use highlighted in result 3. Consequently, it validates that the decision-making assistance tool operates as expected.

Result 1: Base case (phase one)

Indoor temperature satisfaction

The indoor warmth comfort factor evaluates how well individuals in a building can adapt to their comfort levels. Occupants tend to adjust to the average temperature for the month; their comfort would increase if the building’s temperature were close to the monthly average, between 10 °C and 33.5 °C (see Figures 5,6).

Figure 5. Charts indicate the pressure, solar path, and temperature for the Base case (existing case).

Figure 6. Chart indicates heat balance and total fresh air for the Base case (existing case).

Source: Researchers.

Thermal comfort percentage

The thermal comfort rate indicates the proportion of time during the year that individuals inside a building experience comfortable warmth. This rate is established using ASHRAE-55, which outlines the flexible comfort standards, along with the metabolic rates of the individuals involved in common activities based on the design, are considered. The modeling outcomes for the existing AAST Al-Alamein structure demonstrate the subsequent findings: (see Figure 7)

Figure 7. Charts indicate the thermal comfort for the Base case (existing case).

Source: Researchers.

Effective temperature

Operative temperature indicates the calculated temperature at each grid point in the simulation model. The study concentrates on two dates: the summer solstice (January 1st between 12:00 and 11:00) and the winter solstice (December 21st from 12:00 to 11:00). These periods have been selected to emphasize the longest days, illustrating the highest and lowest operational temperatures accordingly (see Figure 8).

Figure 8. Charts indicate the heat balance, temperature, and heat gain for the Base case (existing case).

Source: Researchers.

Agent temperature reflects the computed temperature at each lattice point in the simulation display, with these hours chosen to demonstrate the longest days associated with the max. and min. agent temperatures, respectively.

Energy consumption

Examining energy usage assesses the total energy utilized by the building. The demand for cooling is established based on the typical hardware arrangement for the region, and the occupancy layout is obtained from the individuals present in those areas. The main types of energy use in structures are being heated, cooled, and illuminated.

Adjusted energy equilibrium

The energy requirements for heating and cooling are closely linked to external temperatures. The necessity for cooling begins to increase in March, steadily rising until it reaches its highest point in July when temperatures are at their peak, and then it gradually declines again by October. The energy needed for heating commences to be used in November, consistently increasing until it reaches its highest point in January, the coldest month, and then slowly declines until April (see Figure 9).

Figure 9. Charts indicate the internal gain, Fabric and ventilation for the Base case (existing case).

Source: Researchers.

The findings reveal significantly elevated numbers for the chamber; hence, the Chamber Results are excluded. After a closer examination of the results, it has been established that the devices employed in this simulation are inadequate for assessing intricate building physics, including convection within the chamber. In summary, Table 4 presents the characteristics regarding the design of the current structure difficulties.

Result: Identified solutions

Material selection

The choice of frameworks for constructing envelopes for structures in coastal urban areas depends on factors such as unique material properties, the site’s natural environmental conditions, access, and exposure. This study concentrates on DGVS in coastal urban areas, especially in Alexandria. Choosing the right fabric means selecting materials made in Egypt or neighboring countries that have characteristics suitable for the local climate. This method aids in lowering carbon dioxide emissions related to material sourcing, enhances the local economy, and motivates architects and decision-makers to select favored materials.

Result 2: Vertical living green wall design proposal

vertical living green wall design

Following the identification of the issues with “the current building design (result 1A)” and “exploring possible solutions (result)”, the implementation of the vertical living green wall is suggested (result 2). The vertical green walls include an irrigation system component and a metal hat channel serving as a mounting panel for the stainless-steel wire grid, which is positioned above the planter boxes designed to contain the pre-vegetated plants, as illustrated in Figure 10.

Figure 10. Exploded diagram of Vertical green wall design.

Source: created by Researchers.

Suggested structure of building simulation: comparison of results

Conducting simulation runs once more after integrating the green wall system to evaluate the effects of this scenario against the previous case (base case) outcomes (1) of the current building concerning Indoor temperature comfort and energy consumption as detailed below:

Percentage of thermal comfort

The proposed vertical green wall design has significantly increased the thermal comfort percentage to a 24.5% level with external windows facing north, west, south, and east. The total number of rooms that achieve at least 30% thermal comfort has increased from 13% to 57%, as illustrated in Figure 11.

Figure 11. Site data about temperature and pressure after applying vertical green walls.

(b) Thermal comfort percentage of a proposed vertical green wall (VGW) to building envelope design. Source: Researchers.

Active temperature

There is a noticeable difference between the minimum and maximum temperatures (24 °C). This particularly high temperature is concentrated on the western side, which is crucial to acknowledge. Although the hot zones stand out more, the variations between the lowest and highest temperatures are minimal (16 °C). When assessing the existing building configuration against the GW plan, the count of rooms at temperatures of 28 °C has dropped from 8% to 3 %, as shown in Figure 12.

Figure 12. (a) Temperature graph to show the decrease of temperature after Appling VGW. (b) Temperature table to show the decrease of temperature after Appling VGW.

Source: Researchers.

Energy consumption: standardized energy equilibrium

Energy consumption has decreased substantially, as illustrated in Figure 13. The need for lighting has decreased by 7.04% in summer and 4.67% in winter. A segment of energy is utilized for different industrial needs over the course of the year.

Figure 13. Energy consumption after using VGW design.

Source: Researchers.

Result 3: Dynamic vertical living green wall design proposal (integration of the previous case with louvers)

Dynamic vertical living green wall design

Proposed simulation of the building: comparison of results

The building simulation is executed again after implementing the green wall system to analyze the results of this instance in comparison to the previous case (base case) results (1) of the existing building concerning thermal comfort indoors and energy usage as outlined below:

Percentage of thermal comfort

The percentage of thermal comfort has notably risen with the suggested vertical green wall design for 40% comfort in spaces with external windows oriented towards the north, west, south, and east. The number of rooms that achieve 45% thermal comfort has grown from 13% to 57%, as illustrated in Figures 14,15.

Figure 14. (a) Site data about temperature and pressure after applying dynamic vertical green walls. (b) Thermal comfort percentage of a proposed dynamic vertical green wall to building envelope design.

Source: Researchers.

Figure 15. (a) Site data about temperature and pressure after applying dynamic vertical green walls. (b) Thermal comfort percentage of a proposed dynamic vertical green wall to building envelope design.

Source: Researchers.

Operative temperature

There exists a notable disparity of 35 °C between the highest and lowest temperatures. This intense heat predominantly affects the western area, making it essential to address this issue. While the hot zones are more noticeable, the variation between the minimum and maximum temperatures is relatively small at 20 °C. In comparing the current building layout with the GW design, the number of rooms at temperatures of 30 °C has dropped from eight to three, as illustrated in Figure 16.

Figure 16. (a) Temperature graph to show the decrease of temperature after Applying dynamic green walls. (b) Temperature table to show the decrease of temperature after Applying dynamic GW.

Source: Researchers.

Energy consumption: standardized energy equilibrium

Energy usage has notably diminished, as shown in Figure 17, with a portion of energy being employed for various industrial activities throughout the year.

Figure 17. Energy consumption after using dynamic green walls design.

Source: Researchers.

Before and after applying kinetic green wall louvers

Green coverage calculations

In the calculations for DGVS coverage, only the exteriors of outdoor structures and boundary walls are considered. Since each elevation is made up of various façades that differ in height, the area of each wall has been determined individually by calculating the product of its width and height. These numbers are subsequently added to those of the same to make the calculations easier. Next, the openings were deducted from the total area of each elevation to determine the projected green coverage for each, leading to the following results (refer to Tables 5,6): Total outdoor green coverage = 4036 + 729 = 4765 m². To calculate WWR (window to wall ratio) (see Figures 18,19,20)

Figure 18. Proposal before applying the green wall louvres.

Source: Researchers.

Figure 19. Proposal After applying the green wall louvres.

Source: Researchers.

Figure 20. Charts illustrate the cooling and heating load, RH% and Co2 emission Readings.

Source: Researchers.