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PLEA 2024 WROCŁAW
(Re)thinking Resilience
Climate Resilient Vertical Green Façades
Shading Strategies for Vegetation on Building Skins
CANSU IRAZ SEYREK ŞIK1,2, BARBARA WIDERA2
1Doctoral School of Wroclaw University of Science and Technology, Wroclaw, Poland
2Wroclaw University of Science and Technology, Faculty of Architecture, Wroclaw, Poland
ABSTRACT: Vertical green façades provide many benefits to the urban biotope, such as improving air quality,
reducing the urban heat island effect, providing sustainable stormwater management, creating habitat for insects
and animals, contributing to food production, and positively affecting the psychology of urban residents. However,
these façades are also adversely affected by extreme climatic events. In this paper, the authors examine shading
strategies to increase climate resilience of these façades, and in particular to protect them from sudden heat
waves. Three main strategies identified by authors, i.e. passive shading, kinetic self -shading and shading with
kinetic layer, are qualitatively analysed and their compatibility to vertical green façades is evaluated. The research
results shown that shading with kinetic layer has been the most effective strategy in terms of function, aesthetics,
adaptability, and protection. Kinetic shading layer can provide various shading scenarios such as equal, full or
partial shading unlike passive shading and require less energy compared to the kinetic self-shading. The paper
underlines the gap in the literature on this subject and emphasises the importance of future works on conceptual
framework and parametric design for shading strategies.
KEYWORDS: Vertical green façades, Shading strategies, Climate resilience, Kinetic shading
1. INTRODUCTION
Climate change and global warming affect
negatively the quality of life of human and non-human
inhabitants of ecosystems. Architects and urban
planners come up with design ideas that can reduce
the energy demand in buildings and mitigate urban
heat island effect, while increasing user comfort and
safety. Abundant living systems introduced in urban
zones are among key drivers towards reduction of
Anthropocene impact on climate. Vertical green
façades in the urban tissue, improve air quality,
increase relative humidity, and decrease the
temperature, thus lowering the need for cooling.
Further benefits of green façades include sustainable
rainwater management and grey water treatment,
noise reduction, enhanced biodiversity, and potential
for urban farming [1].
Even though vertical green façades contribute to
climate change mitigation, they are affected by the
heat waves. Unpredictable temperature changes and
exposure to extreme solar radiation cause heat stress
in plants. Extreme climatic events, such as heat waves,
frost, drought, and flooding, can affect plant
production and induce mortality. Moreover, even if
plants survive the heat extremes, they close their
stomata, which means cooling by evapotranspiration
decreases, and depress photosynthesis. Plants can
change their physiology in response to drought to
adapt and survive, for example by elongating their
roots [2]. However, this biological adaptation feature
is not effective on many vertical green façade types
since the depth of the growth medium is limited. This
means that artificial irrigation must be increased to
prevent drying. Furthermore, the excessive direct
solar radiation increases water loss of growth medium.
This makes vertical green façades consume a lot of
water, which is undesirable [3]. Therefore, it is
necessary to protect the façades’ vegetation from
excessive heat causing drought through solutions that
can enhance their climate resistance.
Heat waves reduce yields in agricultural crops. In
corn plants, the heat wave causes significant
reductions in cob length and mass of the cob as well as
the husk which in turn leads to a significant reduction
in total reproductive biomass by 16% [4]. In the
experimental vineyard studied by Martínez-Lüscher et
al. [5] the Cabernet Sauvignon grapes were exposed
without shade to a 4-day heat wave 21 days before
harvest, resulting in 25% of the clusters being
damaged, regardless of irrigation amount.
Furthermore, the study indicates that berries in the
vineyard suffered a great loss of anthocyanins and
flavonoids even if they were not damaged by direct
solar exposure. The study concludes that partial
shading can have a positive role in the retention of the
grape's skin flavonoids in a high-temperature scenario.
These results indicate that, taking precautions such as
partially shading against extreme heat and inadequate
irrigation, especially in vertical gardens used for urban
farming, can improve vegetation diversity and quality.
However, the existing literature on this topic is
scattered and fragmented. Thus, the strategies to
ensure climate resilience of vertical green façades
need to be further explored.
The authors of this paper propose and discuss
design strategies that can boost climate resilient
vertical green façades. These approaches are based on
three main objectives: plant loss prevention, water
savings and increased variety as well as quality of crops
when used for urban farming. In line with these
objectives, three shading strategies aimed at providing
more stable and comfortable living conditions for
vertical green façades, are analysed.
2. DESIGN STRATEGIES FOR CLIMATE RESILIENT
VERTICAL GREEN FAÇADES
Within the scope of the study, the extensive
literature review on existing shading methods and
technologies applicable to building skins was carried
out. Journal articles, conference proceedings and
reports about 'Shading strategies for building façades',
'Shading and passive cooling' or 'Climate resilience of
vertical green façades' have been searched in Web of
Science database for the last ten years. The first
observation from the review is that there is a lack of
research on the climate resilience of vertical green
façades. This issue has been widely addressed in terms
of the climate resilience provided by vertical greenery
to the urban environment rather than in relation to
design strategies that can provide climate resilience
for vertical green façades. The idea of shading to
vertical green façade has not been extensively
explored so far. The limited number of shading
solutions for greenery has been mentioned in this
study. To diversify the alternatives and identify the
most suitable one to provide climate resilience, the
most promising shading solutions, for vertical green
façades have been selected for further comparative
analysis. This qualitative comparison is focused on
advantages and disadvantages of the shading
strategies as well as on their compatibility to
requirements of vegetation on building skins. The first
aspect considered in this analysis was that the plants
need to be able to reach 400-700 nm spectral range of
daylight necessary for photosynthesis, while being
protected from excessive solar radiation and
overheating during the summer season and occasional
heatwaves. The preliminary research revealed that the
key element in the design strategy is the light
transmittance of shading elements which should be
selected according to the requirement of the plant
species. Moreover, even in shading stage, the plants
should still be provided with sufficient ventilation.
Finally, the influence of moisture from plants
evapotranspiration and substrate surface evaporation
on the shading elements’ behaviour must be
considered.
Three of the main solar control strategies for
buildings, which are self-shading via the building
envelope, passive shading with external or internal
devices [6] and active shading with movable shading
devices [7], have been adopted to the vertical green
façades.
The first analysed strategy is passive shading.
Passive systems involve horizontal and vertical shading
elements placed at regular intervals according to the
orientation of the vertical green façade to provide
constant shading for plants. Shading devices such as
overhangs, horizontal or vertical louvers and panels,
various egg-crate systems, vertical outer planes,
horizontal multiple blades or panels and combination
of these different solutions exemplified by Kirimtat et
al. [8] and Valladares-Rendón et al. [6] are generally
used for passive shading on building façades. These
devices might be built as integrated modules to
vertical green systems or as a second layer in front of
greenery to create a secondary skin as shown
respectively in Figure 1a and Figure 1b. The VertiKKA
project [9] represents an example of the
aforementioned strategy. The photovoltaic films are
placed in front of the vegetation, aiming to protect the
greenery from extreme weather and high levels of
solar radiation while allowing for energy generation in
the system. In order to provide homogenous shading
to the vertical green façades, mashrabiya style shading
devices, traditionally used in the warmer regions,
especially in Middle East, can be applied as shown in
Figure 1c [10].
The second strategy focuses on self-shading of the
building envelope achieved by the protrusions on the
envelope to place transparent surfaces more inward
[6]. In order to provide self-shading to vertical green
Figure 1: Passive shading strategies: (a) Horizontal shading panels attached to vertical greenery (b) Horizontal shading
panels as secondary skin (c) Mashrabiya style shading for greenery (Source: Authors).
a
b
c
façades, these protrusions can be formed through the
movement of the vegetated façade modules with
adjustable angles, as shown in Figure 2. In such
systems, modules can be positioned horizontally and
vertically depending on the orientation of the vertical
green façade. During winter, when the sun’s position
is lower these vegetated modules can mimic the sun-
capturing motion as seen on the Adaptive Solar Façade
developed in ETH Zurich [11]. In summer, the panels
can move to the opposite direction to avoid exposure
to excessive solar radiation during heat waves.
The third strategy is based on the kinetic shading
layer added to the vertical green façade systems as
presented in Figure 3. This kinetic shading layer can be
constructed from various materials and controlled
either automatically by sensors, manually by the user
via a central computer or by interconnected panels
consisting of units working as sensing and activating
elements [12]. Shading elements can perform
different types of movements such as flapping, folding,
rotating, sliding according to the design of the system
[13]. These elements can change the pattern and
transparency ratio (e.g., the Tessellate system) [14].
Sliding foldable louvres that allow airflow and provide
partial shading or wings that flutter on the vertical or
horizontal axis (e.g., kinetic façade of Campus Kolding
designed by Henning Larsen Architects [14]) can be
used to create a shading layer. These shading elements
can also be constructed using natural materials, such
as wood and bamboo, as seen in the kinetic façade of
the Aalen University Extension building designed by
MGF Architekten [14] and the Carabanchel Social
Housing building designed by FOA (Foreign Office
Architects) [14].
3. COMPARATIVE ANALYSIS OF DESIGN STRATEGIES
3.1 Advantages and disadvantages of design
strategies
The passive shading method is based on traditional
façade shading concepts used e.g. in Mediterranean
countries. In traditional shading systems applied for
agricultural purposes on horizontal fields, the plants
are fully covered with light cloth or porous fabric. If the
shading material selection does not properly consider
the needs of plants, satisfactory yield cannot be
obtained due to insufficient amount of daylight and
fresh air [5]. Such an uninterrupted stable shading
layer is not necessary for vertical planting surfaces.
Passive shading devices can provide sufficient shading
without completely disconnecting the vertical green
façades from the external environment.
Passive ventilated shading is easy to implement
and relatively inexpensive [15]. Solar panels, such as in
the VertiKKA project mentioned above can be
integrated with vertical green systems to generate
electricity [9]. However, the disadvantage of these
shading elements is that their position cannot be
changed. This hinders the system’s response to user
requests and sudden changes in weather conditions
[15].
In kinetic self-shaded modules proposed by the
authors, the plants can be shaded, when necessary
(e.g. during hot periods), while receiving sufficient
daylight during colder periods (when sun rays fall at a
more oblique angle). In addition to the effective
utilisation of daylight, another advantage of this
strategy is the ease of access for humans and animals
since the system is not interrupted by an external fixed
shading layer. If different modules respond
individually and move in the opposite directions within
Figure 3: Kinetic shading layer on green
façade (Authors)
Figure 2: Kinetic self-shaded planted panels (Authors).
the same time frame, plants that require different
amounts of sunlight can be grown in parallel. This
practice may help increase the variety of crops
obtained from the system. On the other hand, the
system has several limitations. Variables due to the
requirements of plant biology and the mobility of the
system create design complexity. System movement
requires extra energy consumption. The possible
weight of vegetated modules is another disadvantage.
The costs of maintenance and repair of the mechanical
parts may increase the price of kinetic systems [16].
Among analysed shading strategies for vertical
green systems, the kinetic shading layer demonstrates
the highest adaptability to the climatic changes. Unlike
passive shading devices, kinetic layers can respond in
multiple ways to heat waves, sudden precipitation and
strong winds. This concept can provide equal, full or
partial shading for plants and growth medium. If plants
with diverse light requirements are located in the
same vertical green system, with the application of
kinetic layer several shading scenarios can be created
for different plant species. Depending on the material
and the design of the shading element, the kinetic
shading layer systems are lighter than kinetic self-
shaded green façades and the movement of elements
requires less energy. If the kinetic shading layer is
designed without consideration of the requirements
of plant biology, human and animal interaction and the
external environmental conditions, problems arise in
the functionality of the system. This results in high
maintenance and repair costs. However, if the
necessary requirements are applied into design,
maximum efficiency can be obtained with the kinetic
shading layer compared to other strategies.
3.2 Design requirements of shading strategies
The types and sizes of shading devices used in
building façades should be designed considering the
altitude and angle of the solar radiation (in relation to
location and façade orientation), the required amount
of daylight and the size of shaded area [15, 17]. These
considerations establish the basis for design of passive
shading devices for vertical green façades too. Design
configurations for these devices should be determined
taking into consideration the plants’ needs and the
maintainability requirements of the system.
Accessibility for maintenance purposes such as
cleaning and repair, gardening and plant care,
irrigation and drainage should be provided to users
[18]. If shading devices are integrated into the vertical
green façade, the distance required for the growth of
the plants should be considered. Especially, there
should be a gap between the horizontal panels and the
first row of plants according to the maximum growth
distance of the plant type. Where fixed shading
elements or mashrabiya style shading devices are used
to form a second skin, a gap should be left between
the shading layer and the green façade to allow human
access to these façades for maintenance, planting, and
harvesting. Due to the inability to change position of
passive shading devices, the light requirements of the
plants must be assessed when selecting the materials
or shade-loving species should be preferred.
The module’s angle should be arranged considering
the plant metabolism in a shading condition of kinetic
self-shaded systems. In order to prevent damage to
the plants during the module’s movement, the size of
the modules and the gaps between them should be
designed taking into account the maximum
dimensions of plants and their growth processes.
Furthermore, materials that tend to fall cannot be
used for this system. Drainage must be designed
according to the movement of water for the various
module positions. The weight of the planted modules
and the energy required for their movement needs to
be considered and sustainable energy generation
methods should be integrated into the system.
The design parameters of the kinetic shading layer
include geometric shape and motion type, technology,
structure and material [12, 19]. The choice of
geometry and movements of kinetic façades are
influenced by numerous factors such as the function of
the system, the required indoor conditions of the
building, the requirements of the designer and users
as well as environmental and climatic conditions. In
order to design geometric shape of kinetic shading
devices, architects utilise design methods such as
parametric design, performance-based design,
generative design, approaches such as biomimicry and
patterns such as origami or criss-crossed patterns of
latticework in mashrabijas [13, 20, 21]. In the same
way, different design methods and inspirations can be
used by designers for the kinetic shading layer of
vertical green façades.
The technologies applied in kinetic façades consist
of control, sensing and actuating elements. Façade
movement can be activated via pneumatic, hydraulic,
material-based, passive actuators or servomotors.
Control can be provided via hand-operation, via
central computer or interconnected panels by
microcontrollers (decentralized control) [22]. In
material-based technologies all the sensing, actuating
and control features are provided by material itself.
These materials include shape memory alloys, shape
memory materials, etc. [12].
User interaction with the control mechanism of
kinetic shading devices is beneficial for climate
resilience and maintainability of vertical green
façades. In addition, it is advantageous to open the
kinetic shading layer to allow user access during
planting and harvesting. This may represent a
challenge in the case of material-based technologies
that automatically respond to changing environmental
conditions since their actions cannot be programmed
by the user.
The advantage of these technologies is performing
all sensing, actuating, controlling actions and reducing
the complexity, cost of construction, maintenance,
production of kinetic façades. Moreover, this
technology mostly does not require an extra energy
source [23]. Therefore, the integrated use of material-
based technologies with other technologies that allow
user interaction can provide a shading layer that can
be controlled when it is necessary but still requires a
minimum of energy use. The evapotranspiration and
evaporation effects of the vertical green façades
should be considered during the material selection.
The shading elements must enable the air flow
even in the fully closed position when still providing
protection against strong winds. For the healthy
growth of the plants and the comfort of other living
creatures on the vertical green façades, an optimum
gap should be left between the kinetic shading layer
and the vertical green façades. The materials of the
shading modules affect the durability and functionality
of the system. Pirouz et al. [24] integrated a mesh into
the vertical green façade surface for fog harvesting
and have proven that atmospheric water harvesting
for green façade irrigation is possible. Similarly, the fog
harvesting mesh can be integrated into the kinetic
shading layer and prevent vertical green façades from
being dependent on tap water in periods of
insufficient precipitation. Materials should be
corrosion resistant. It is possible to conclude that the
kinetic shading layer strategy allows for more flexible
design options.
4. CONCLUSION
Shading systems aimed at protecting vertical green
façades against the negative effects of global warming
have been comparted. Because the initial analysis
revealed that this concept remains largely under-
investigated. In this study, this research gap has been
identified and addressed. The methodology and main
findings of the study have been visualized in Figure 4.
The result of this study revealed that passive
shading strategies have lower initial cost and are easy
to build but their response to changing climatic
conditions is limited. When passive shadings are used
for green façades, it is important to ensure that
shading effect will reach to the rooting medium such
as containers or plant pots to protect them from
overheating the and water loss.
Kinetic self-shading demonstrates adequate
climate responsiveness. With the absence of an extra
layer in front of vegetation, the interaction of human
and non-human beings with vegetation is possible and
remains uninterrupted. Due to the higher weight of
kinetic modules, the mechanical and electrical
elements require more maintenance and repair while
increasing the total energy consumption of the
system. Kinetic shading layers offer more flexibility in
terms of design (e.g. in relation to function, aesthetics,
adaptability and protection). This system, when
properly designed, requires less energy than kinetic
self-shading solutions. Kinetic shading layers provide
various shading scenarios such as equal, full or partial
shading. Furthermore, the design of irrigation and
drainage is less complex than the kinetic self- shading
solution since the vertical green system is stable.
Therefore, it is indicated as the most effective solution
in this study.
Figure 4: Methodology and main findings of the study (Authors).
However, the complexity of kinetic systems in
terms of design and construction as well as potential
high cost of maintenance compared to the passive
systems should be considered. In the case of full
shading, further observation on the prototype in the
real-life conditions if the kinetic shading layer does not
interrupt the interactions of the plants with birds,
pollinators, etc.
Further research is necessary to develop
conceptual frameworks allowing for correct system
adjustment to climate and functional requirements.
The effects of shading strategies should be
investigated by simulative or experimental studies.
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