Introduction
Paper Methodology
Vertical Greening System (Green Wall)
Vertical Greening Systems Technical guides and Policies Review
Green Facades Environmental Benefits Efficiency Experimental Study
Conclusion
Introduction
In the new urban development which facing a lot of challenges such as; energy, increasing in population and built up area ratio, the Vertical Greening System (VGS) could be used as a one of Green areas restorative tool playing and also as an environmental building retrofitting tool according to its ability to maximize the thermal comfort and energy saving ratio, work as a thermal insulation for buildings envelope, reduce the heat gain/loss in the indoor spaces, minimizing CO2 emissions, reduce noise … etc. [1].
Although, the VGS has a huge environmental benefits, most of residents/users reject the idea of transferring the horizontal gardens into a vertical gardens also, some of them afraid from its effect on the building structure and others afraid from its installation and maintenance cost which shows that the social aspects considers as one of the important aspects to achieve the successful VGS Installation as an environmental and economic aspects [2]. Despite the GFS benefits especially in the hot dry climate such as Egypt the lack of Technical guides is a relevant factor that could affect the development and the dissemination of VGS and particularly of GFS.
The Aim of the Paper to define the requirements of a technical guide focused on GFS as it affects directly energy consumption efficiency (as shown in the experimental study) and Environmental benefits regarding environmental specifications to be taken into account over the GFS’ life cycle.
Paper Methodology
In this paper GFS effect will be investigated through literature review to introduce the GFS types, structure systems, and maintenance tasks it also will compare between the different exiting technical guides to define a design guidelines to be able to reach an Installation Process Chart. Then the analytical method through analysing the case studies and showing the GFS installation environmental effectiveness. Finally, measuring the GFS environmental benefits through a DesignBuilder simulation for a residential building in 6th October City, Egypt before and after using GFS on 12 and 25 cm wall at west and east direction (Figure 1).
Vertical Greening System (Green Wall)
Green Walls or Vertical Greening Systems (VGS) are the term that refers to all the surfaces that vegetated vertically, the previous researches subdivides Vertical Greening Systems (VGS) in two main systems: Green Façades (GFS) and Living Wall Systems (LWS) [3].
There is an evident difference between GFS, where it used climbing plants to grow along the wall and covering it, and the most LWS, which it includes different materials and technology to support a wider variety of plants and creating a uniform growth along the surface also its plants are receiving the water and nutrients from the vertical support instead of from the ground. [3]
Green Façade System (GFS)
GFS is a system which climbing and herbaceous plants are used to cover the supporting structure or grow directly on the facade. It takes 3-5 years to give full coverage of the facade. [4] It divided into two categories;
Grow direct into the soil in the ground [5]
Grow in the substrates [6], plants can at the bottom or at the top of the façade. [7]
Green Façade Structure Systems
The structural system of GFS could be either metal, wood, or plastic containers connected to the facade by Horizontal, vertical, or pivot arbores. It could be 2D, such as: cables, wires and networks, or 3D, such as: Rigid Frames and Modular Trellis. [8]
Modular Trellis panels system
It consists of lightweight standard rigid, 3D panels that are manufactured of welded galvanized steel wire & supports vertical extension of plants [9]. This system is designed to hold GFS with leaving span between structure and wall or and as a freestanding green walls [9] (Figure 2).
Cable and wiring networks system
It cables are used to support fast growth plants with denser foliage and Wires to support slow growth plants. Plants can be at the bottom or at the top of façade which called “Hanging System”. [12] (Figure 3).
Green Façade Plants Species
To insure GFS success suitable plants should be chosen also, the facades shouldn’t contain any cracks & openings are kept free of vegetation to prevent damaging. [12]
There is 4 types of vegetation could be used in GFS: [12]
Bonders: self-bonders using clinging roots such as; Ivy (Hedera helix),
Twiners: twining their stem around a support such as; wisteria
Shoots: such as; parthenocissus, grape vine and clematis
Support climbers: such as; climbing rose and Winter jasmine
GFS Maintenance
All GFS need a regular maintenance because they are a live system and the understanding of GFS in building design stage could reduce the maintenance cost with exception of: accessibility and irrigation issues. Also choosing the freestanding removable GFS installation could reduce the use of lift equipment to maintain its components that located in higher floors. [13]
The maintenance budget which determined by customers considered as the main factor that control the choice of plant type and construction system. [13] So that, the indicating of GFS potential in minimizing the energy consumption is must to make them know how it will effect on the building energy cost and human productivity [13].
Maintenance Tasks [14]
According to Australian Growing Green Guide maintenance tasks divided into 5 categories;
The maintenance that happened in the first two years of GFS application which called the Establishment Maintenance, It's for ensure healthy plant growth and it includes irrigation system and plantation maintenance such as; weed and pruning control.
The maintenance for regular works which called Routine Maintenance, It's for ensure that facade is maintained according required standard of functionality, appearance and safety
The maintenance that responsible for building structure and the GFS components such as; hanging system, plantation, soil, irrigation... etc. This called Cyclic Maintenance.
The maintenance that responsible for the sudden damaged and changing the fails parts in the GFS which called Reactive and Preventative Maintenance.
Finally the maintenance that responsible for changing the design intent according to changes the ownerships or the building usage and it's called Renovation Maintenance.
GFS Benefits [15]
The current researches shows that the GFS has a several benefits such as;
•Minimize the energy consumption and Green House Gases (GHG)
•Minimize the Urban Heat Island (UHI) Effect
•Improve the building’s thermal performance
•Improve the indoor and outdoor air quality (IAQ & OAQ)
•Minimize the noise pollution
•Maximize the urban biodiversity and food production [16]
•Improve the health and wellbeing [16]
The following table (Table 1) shows the different benefits of GFS installation
Table 1.
The benefits of GFS
| Environmental Benefits | ||
| Energy Consumption |
- Saving ratio in warm–dry climates 9:30% [15] - Reduce consumption up to 20%. [17] | |
| Thermal performance |
- The evaporation of GFS plants cools the facade by -7°C to -15°C as it work as a sun-screen [15] - Reduce the UHI effect. [10] - reduced indoor temperatures 10 ◦C [18] | |
| Reduction of air pollution |
- Reduce CO2 emissions, NO2 concentration and clean air in city scale [19] - Reduce PM10 (microscopic Particulate Matter) by 15:23% and PM2.5 peak by 45: 71% | |
| Reduction of noise |
- Reduce noise & vibration up to 40dB [13] - Absorb up to 18dB of the street noise. [19] - Reduce noise 5:10 dB & traffic noise 1dB [20] | |
| Water management | - Irrigate by recycled grey & black water or collected rainwater | |
| Social Benefits | Visual Benefits | |
|
- Enhance the urban environment aesthetic value and adds value to building identity. [21] - Improve human health and decrease stress and which led to crime and violent behaviour reduction. [22] |
- Achieved the 3 categories of beauty (enjoyable, admirable and ecological beauty). [23] - Could be used as a public art. [23] | |
| Educational Benefits | Economic Benefits | |
|
- Could be used in biology or art classes in schools or in Sustainability 3D teaching textbooks [24] - Raising the importance of ecology awareness. [25] |
l- Increase the real estate up 20% [26] - Increase residential and commercial by 7:15% [26] - Payback reached after 16 years. [27] | |
Vertical Greening Systems Technical guides and Policies Review
According to the environmental benefits of GFS as type of VGS a lot of policies and technical guides has been established to insure achieving its benefits not only in building scale but also in urban scale.
Policies review
In Germany, Berlin has developed an urban planning parameter called BAF (Biotope Area Factor) since the 1980s which sets out the ratio between surfaces that have an effect on the ecosystem such as; vertical greening systems, green roofs, permeable surfaces, etc. and the total area of the site [14].
In USA, The City of Seattle has established the “Green Factor Program” in 2007, and it’s a score system has been designed to increase the amount of green spaces in new development projects and it depended on the German BAF (Biotope Area Factor) and an urban planning parameter and to get the score your building must equivalent 30% of building area should be vegetated in economical buildings and 50% in multi-family residential [14].
In Australia, the city of Sidney has been adopted the “Green roofs and walls policy”, which provides direction to promote the use of green roofs and walls in both residential and commercial sectors also, vertical greening systems have been recognized in rating tools Such as LEED® building certification programs [14].
In Singapore the “Sky rise Greenery Incentive Scheme” (SGIS) has been launched in 2009 and it finances up to 50% (or 500$ per square meter) of green roofs and VGS installation cost on existing and new buildings. And it also adopted a new legislation to achieve at least 100% plot area greenery.
In Hong Kong, China the government has developed strategies aimed to maximizing the green areas percentage through green roofs and VGS installation since 2004 and in order to enhance the implementation of greenery, it started to develop “Greening Master Plans (GMPs)” which focused on suitable sites for planting vegetation.
In the UK, London has been developed a plan to maximize the green area percentage by 5% in 2030 in the central of London through using green roofs and VGS [14]. So that, the Mayor of London has produced a technical guide that investigates the practical benefits of living roofs and vertical greening systems. And it points out the aspects that need to be considered such as; localization, orientation, requirements for plant, structural capability, etc. [28].
International Technical guides review
According to European CEN/TC 350 standards which related to Environmental sustainability of construction works) the proposal takes into consideration a wider number of stages over the VGS life cycle. CEN/TC 350 is based on a methodology that aimed to achieve transparent description of construction works environmental performances within a life cycle approach. And it could be used for comparing solutions/choices which involving different materials and building systems [29].
Regarding to CEN/TC 350 standards, only 4 technical guidelines give a detailed set of information about Vegetated Façade Systems (green Façade and Living Wall) life cycle stages:
• The Growing Green Guide (Melbourne – Australia) [14]
• The short-guide to safe practices for vertical greenery (Singapore , Republic of Singapore) [30]
• The Végétalisation des murs et des toits (Paris, France) [31]
• The UK Guide to Green Walls (United Kingdom) [28].
The comparison between the 4 guides shows that they are encompassing the following key-topics: benefits, types, design guidelines, installation, maintenance and plant selection. And all of this topics has been assumed because of their relatively frequent occurrence in worldwide policies. Also, the analysis of 4 guides shows that it considered on; On-site operation stage and the information about GFS manufacturing and end-of-life (after removing it) are rather poor
GFS Considerations
After analysing the 4 technical guidelines that mentioned above the GFS consideration could be classified as the following;
1. GFS Architecture Considerations:
• Building Location and Façade Characteristics (with/without opening) are very important to determine suitable GFS, structure system and maintenance tasks [14].
• Architects should be sure that GFS followed open and closed space codes [32].
2. Construction and Structure Considerations: [32]
• Structure Engineers should consider steel frame additional weight in GFS 3D systems
• Structure Engineers should verify the Dead and live loads and confirm the wind to ensure the compatibility of the chosen system with the building construction type.
• Structure Engineers should determine GFS free standing system air gap distance with taking into account the environmental & architectural requirements [33].
3. Environmental Considerations: [33]
• Site inventory is important to determine the suitability of covering percentage, soil availability, sun orientation, drainage, water supply and grey water usage availability.
• Try to integrate between GFS and Green infrastructure techniques (vegetated swale & rain garden) and storm water management to reduce the site water discharge [32].
4. Irrigation and Plants Considerations: [32]
• Determine an Irrigation Plan according to rainfall harvesting, possibility of using grey water, drainage, water supply and finally the chosen plant’s needs.
• The plants in GFS should be choose according to; [32]
• Site Location (Native plants, water supply and drainage availability)
• The type of chosen structure system and façade coverage area ratio
• Plants seasonal cycles and leaf area index (LAI)
• Combination between Evergreen and deciduous vines is must to achieve GFS maximum efficiency in the four seasons.
• The 3D freestanding system is the best choice for Scramblers and root climbing vines
• the twining vines will be best choice in case of there is no air gap or air gap is < 40 cm
5. Maintenance and Economic (Budget) Considerations: [14, 32]
• An written maintenance plan is must for managing a long term of required functions, lasting installation
• Maintenance is important in the GFS that it height exceed 2.50:3.00 meters.
• A Periodical maintenance plan is important in air- gap space <15:20 cm, drip irrigation
• The budget should include; structure system, plants, soil, waterproofing, irrigation, shipping, maintenance and any extra required structural elements.
GFS Guidelines
Design guide lines could be defined through the previous GFS literature review and technical guidelines standards and it could be divided into 6 main points as shown in the (Table 2). [34]
Table 2.
GFS Design Guidelines and Installation Strategy [Source – Researcher]
| Green façade Systems (GFS) Design Guidelines and Standards | ||
| Concept Elements [32] | Architecture Standards | Construction & Structure Standards |
|
Percentage of vegetative coverage Soil volume for long term facade planting survivability |
- Climate condition and installation orientation - Vertical surfaces characteristics - ROW Local building codes & landscape ordinances - GFS components - Compatibility with building design and ventilation requirements - Access to Maintenance |
- Compatibility with building structures - Building structures safety & - waterproofing materials - Availability of drainage and irrigation systems - Weight Loads (Dead and Live Loads) - GFS Height |
| Aesthetics Elements [32] | Economic Standards | Environmental Standards |
|
- Visual Aesthetics - Other Aesthetics |
- Installation and Structure system cost - Plants and its component cost - Building Isolation Cost - Irrigation system cost - Seeds, seedlings and fertilizers Cost - drainage, water resources availability - Maintenance cost - Payback period and ratio |
- Ratio of CO2 emission reduction - Ratio of indoor Temperature reduction - Ratio of energy saving - wellbeing and public health - Ratio of noise reduction - Grey water technology usage |
GFS Installation Process
To be able to specify the suitable GFS and its Components to achieve the required benefits with sufficient cost and payback the VGS Installation Process Chart (Figure 4) is important as it works to define different GFS alternatives according to the architectural and structural building characteristics. Also it could be work as simulation required input data guide and determine the needed outputs.
Green Façade System Technical Guide
The aim of defining the Technical guide proposal suitable for the hot dry climate is to provide technical information to stakeholders concerning the GFS and the users of this guide are: architects, planners, developers, landscape architects, engineers, owners, general contractors & subcontractors, materials and product manufacturers, public authorities, and other building technicians.
After analysing the above different technical guides, The Technical guide proposal should contain 9 main points as the following;
1. Importance and Usage
2. Scope and Definitions
3. Installation and Ecological requirements
4. Project and design
5. Cost and Payback
6. Consideration and Design Guidelines
7. Monitoring and safety
8. Maintenance
9. References
Green Facades Environmental Benefits Efficiency Experimental Study
The Environmental benefits (Energy Saving, CO2 emissions, heating and cooling loads) of GFS has been explored through generating GFS models in Design Builder as it enables to model full details buildings also, it accepted to use “green roof material” to act as a “green façade” with taking into account that Irrigation has no effect in the results [35]. “Trial version is available at: https://designbuilder.co.uk”. The Simulation will enforce “EnergyPlus” climate file via “DesignBuilder” preinstalled weather file [35]. and compute the Environmental benefits for a residential unit located at the 1st floor (to avoid heat gain/loss from ground and roof) in East and West Orientation in both Red Brick Walls Thickness (12 and 25 cm) through the following:
1. After GFS Direct to the Wall Installation
2. After GFS with air gap 60 cm Installation
Experimental Study Input Data
An 85.00 m2 residential unit in housing for youth project which located at 6th October city with 12 cm Red Bricks wall (Figure 5).
The GFS chosen system is a Grid-net system that installed in two alternatives:
• Directly on façade surface, hanging 6 sturdy steel planter box (100 x 500 x 15 cm) contains a pre-vegetated plants sheet with no need to irrigation system
• Free stand system leaving a 60 cm span, hanging 6 sturdy steel planter box (100 x 500 x 15 cm) contains a pre-vegetated plants sheet with a simple self-irrigation system.
The chosen plant is “Hedra Helix – Ivy” with LAI: 0.005 m2/leaf [39] - 100% coverage, Opening: 30% WWR – clear single glazing 6mm, Lighting Energy: 1.00 w/m2, H-VAC: split with no fresh air, occupancy rate: 0.0196 people/m2 and Infiltration: 0.7 ac/h. After checking the VGS installation process chart, (Figure 5) the simulation required data as shown in (Table 3).
Table 3.
wall layers thermal property [38]
| Wall layers | Initial Case | GFS-Direct to the Wall (D)/with air gap 60 cm (A) | ||||||||||
| D | A | D | A | D | A | D | A | |||||
|
Sp.H J/kg.K |
Den. g/m3 |
Cond. W/m.K | Thickness m |
Sp.H J/kg.K |
Den. g/m3 |
Cond. W/m.K |
Thickness m | |||||
| Water vapor [37] | -------- | ------- | -------- | -------- | 1966 | 0.60 | 5.56 | 0.002 | ||||
| Vegetation [37] | -------- | ------- | -------- | -------- | 2.8 | 533,28 | 0.36 | 0.20 | ||||
| Air gap [37] | -------- | ------- | -------- | -------- | -- | 1004 | -- | 1.3 | -- | 5.56 | -- | 0.60 |
| Stainless steel | -------- | ------- | -------- | -------- | 460 | 7900 | 17 | 0.05 | ||||
| Softwood [37] | -------- | ------- | -------- | -------- | 1880 | 110 | 0.14 | 0.015 | ||||
| Plaster | 1000 | 600 | 0.16 | 0.005 | 1000 | 600 | 0.16 | 0.005 | ||||
| Mortar | 896 | 1570 | 1.00 | 0.02 | 896 | 1570 | 1.00 | 0.02 | ||||
| Red Bricks | 838 | 1790 | 0.60 | 0.12 | 838 | 1790 | 0.60 | 0.12 | ||||
| Mortar | 896 | 1570 | 1.00 | 0.02 | 896 | 1570 | 1.00 | 0.02 | ||||
| Plaster | 1000 | 600 | 0.16 | 0.005 | 1000 | 600 | 0.16 | 0.005 | ||||
Design Builder (Simulation Program
DesignBuilder is a software to measure the environmental performance efficiency of new and existing buildings, it also one of an easy-to-use simulation software that helps you to quickly measure the environmental performance of new and existing buildings [39].
Models could be imported from BIM programs such as (Revit) or built quickly by using the program’s tools. It provides a fully integrated performance analysis including: energy and thermal comfort, design optimization, HVAC, day lighting (natural and artificial), cost, CFD, BREEAM and LEED credits, and reports that taking into its consideration the several national building certification standards [39].
Results and Discussion:
For investigating the benefits of GFS, simulations were carried out with all exposed walls and vegetation. The study was focused on Energy saving, CO2 emissions, heating and cooling loads of the building in East and West Orientation.
Environmental Benefits
1. Energy Saving: Most of residential building use only 12 or 25 cm of red brick in outer walls with U-value of 0.42 & 0.5 W/m2-K, to enlarge inner spaces area ignoring the Egyptian code so that, the research aims to use GFS as an eco-friendly retrofitting solution to achieve thermal comfort with saving in energy consumption (Table 4).
Table 4.
Annual energy consumption and saving ratio for West and East orientation [Source - Researcher]
2. CO2 Emissions: GFS maximize the indoor and outdoor air quality according to its ability to purify the surrounding air and decrease the CO2 emission as shown in (Table 5).
Table 5.
Annual CO2 emissions at West and East orientation [Source - Researcher]
3. Heating and Cooling Load: The GFS has a great effect on minimizing heating and cooling loads as shown in (Table 6) according to its ability to minimize the heat gain/loss inside spaces and also work as a thermal insulation for the outer surfaces.
Table 6.
Annual heating and cooling loads at West and East orientation [Source - Researcher]
Economic Benefits
The GFS components and installation cost has been quoted as the following; [39]
• The Total Cost for direct GFS is 7300 EGP with maintenance cost 1400 EGP/Year
• The Total Cost for GFS with 60 cm air gap and irrigation system is 9650 EGP with maintenance cost 1100 EGP/Year.
As the average monthly consumption for initial case is 400:470 KWh & for GFS installation is 300:350 KWh and the 1 KWh for 201:350 KWh consumption cost 0.70 EGP and for 351:650 KWh consumption cost 0.90 EGP [40] the cost Payback will be as shown in (Table 7).
Table 7.
Annual electricity bill payment and saving ratio for West and East orientation [Source - Researcher]
Conclusion
The green façade systems (GFS) has a lot of positive benefits not only in energy consumption but also, in the other environmental benefits. So that, a lot of countries try to established policies and technical guides suitable with its climate conditions to be easy to architects and designer to integrate the GFS technology with building design and insure achieving the maximum benefits and also to offer a new way to green the built environment with minimizing it energy consumption cost. Also the paper outcome in the part of defining the main points in technical guide could be used as a first framework to make available harmonized information to the stakeholders engaged in design, off-site/on-site production, and operation and repair.
Also the paper shows how the GFS installation effect on Building’s energy consumption cost trough using DesignBuilder software to measure GFS effectiveness such as; reducing in energy consumption, CO2 emission, heating and cooling loads and the VGS installation process to define the steps and the result of installation (Figure 6).
The installation results show that retrofitting for the existing building is could be done by using GFS (direct or with 60 cm air gap) as it shows that GFS works better on 12 cm wall than 25 cm in maximizing energy saving which was predicted, due its lower thermal mass also, it shows that GFS installation on 12 cm wall achieved higher reduction in energy consumption, CO2 emissions, heating and cooling loads in west direction than east direction.
In west direction: GFS (direct or with 60 cm air gap) installation on 12 cm wall saved energy by 19:23.7% & by 13:18.8% in case of changing wall thickness to 25 cm. CO2 emissions reduced by 12.6% in direct GFS on 12 cm wall while, in GFS with 60 cm air gap by 18%. According to GFS ability in minimizing the heat gain & loss through external surfaces, heating loads reduced by 18.8% & cooling loads by 19% in direct GFS on 12 cm wall while, in GFS with 60 cm air gap heating loads reduced by 22% & cooling loads by 24.6%. And in east: GFS installation saved energy by 17.5:19.7% on 12 cm wall and by 11.3:16% in case of changing wall thickness to 25 cm, CO2 emissions reduced by 11.3% in direct GFS on 12 cm while, in GFS with 60 cm air gap by 16.8%, heating loads reduced by16.8% & cooling loads by 17.6% in direct GFS on 12 cm while, in GFS with 60 cm air gap heating loads reduced by 18.8% & cooling loads by 22.7%
Finally According to energy consumption, CO2 Emissions, heating & cooling loads reduction the annual electricity bill payment reduced by 35% in direct GFS installation on 12 cm at west while in GFS with 60 cm air gap reduced by 38.7% and in east it reduced by 29% in direct GFS installation on 12 cm while, in GFS with 60 cm air gap reduced by 31.8%
