A framework for the design of bioinspired building envelopes:
case study of an adaptive skin inspired by the morpho butterfly
Tessa Hubert 1) 2) 3) *, Tingting Vogt Wu 2), Antoine Dugué 1),
Denis Bruneau 3), Fabienne Aujard 4)
1) NOBATEK/INEF4, National Institute for the Energy Transition in the Construction sector, France
2) University of Bordeaux, I2M, UMR 5295, Talence, France
3) Ecole Nationale Supérieure d’Architecture et Paysage de Bordeaux, Talence, France
4) MECADEV UMR CNRS 7179 - National Museum of Natural History, Brunoy, France
*Corresponding author: firstname.lastname@example.org
Building envelopes have a key role to the occupant comfort. Their design, implementation and functionalities
highly influence the overall building performance. Some current research focus on strategies to improve
buildings energy efficiency while minimizing their impact on the environment. Bioinspiration i.e., the inspiration
of biological organisms for technical solutions, has been for the past decades an emerging field in the building
construction. Living systems are the results of successive adaptations that occurred during the last billions of
years to sustain under a constrained environment. They usually demonstrate optimization strategies rather
than maximization, including adjusting to climatic variations and managing multiple physical factors, such as
heat, light, air with local natural and renewable resources. While the potential of bioinspiration for the building
sector is beyond doubt, its implementation still needs developments, as the transfer of a biological principle to
a technical solution often requires scales and materials transpositions to technology. This paper presents a
bioinspired design issued from an experimental framework; the authors first selected and characterized
biological models, then used the generated data during a conceptualisation workshop gathering engineers and
architects. It emerged a concept of an adaptive double-skin building envelope, inspired from the morpho
butterfly, that can manage heat and light transfers towards the building envelope.
Keywords: bioinspiration, adaptive skin, product design, parametric, regulation factors, biological models.
1.1 Bioinspiration and architecture
The building envelope can be defined as a separator between the conditioned and unconditioned
environments. It is composed of multiple systems, walls, roofs, windows, or foundations, which all have
hierarchical structures and layers  hosting specific functions in response to a wide range of environment
solicitations. Aiming at adapting the envelope system for an improved performance, adaptive envelopes i.e.,
reacting in real time to environmental changes, have therefore become a growing interest in the building area
–. In particular, recent research has been focusing on bioinspiration, a creative approach based on the
observation of biological systems , as a promising field for adaptive solutions.
Living systems have evolved under multiple environmental pressures such as climate changes, scarce
resources or competition. They have developed efficient and multi-functional features. Some of those have ,
already inspired multiple innovative designs in the architecture field . However, the functions or strategies
resulting from the chosen biological models during the architectural design processes are sometimes poorly
abstracted, resulting in monofunctional concepts  or hardly achievable systems . This paper describes a
framework designed to overcome some of the abstraction challenges, from the biological domain towards
architecture and engineering applications. Workshops using this framework were then organized and we
present here the full process illustrated through an example of a building envelope element design, inspired
by the morpho butterfly intrinsic properties and behaviour features.
1.2 Existing frameworks
There are two ways to approach the design process of bioinspiration: either through a technology-pull
approach, meaning addressing first a design problem and seeking the solution in strategies of nature, or
through biology-push, which is using biological findings as a starting point and transferring them into
engineering designs . While the biology-push approach is generally based on serendipity, the technology-
pull appears as the most suitable approach for systemic and widespread use in an industrial setting, since it
starts in a technical environment .
For either approach, there is extensive research on frameworks, tools and methods to support the bioinspired
design process –. They include databases or alternatively thesaurus, linguistic or semantic tools allowing
back-and-forth between the involved biological domain and design concepts . However, few of these tools
were developed for architectural purposes. Although some of the design processes can be adapted to the built
environment, designers are still widely challenged with 1) the selection of biological models to address multiple
requirements that are sometimes contradictory  , and 2) how to actually combine the chosen functions or
strategies into a design that can be implemented into a building . Today, even though transposition from a
biological model to a technological design is assisted by recent progress in materials and innovative
construction techniques –, it is in practice very often unachieved; the benefits provided by the
bioinspired design do not counterbalance the resources or means at stake for its implementation.
This research is an application of a bioinspiration design framework, with the objective of developing an
adaptive and multi-functional building envelope as a product. As a starting point, the authors chose to explore
the biology-push approach adapted from the design process described by the ISO standard 2015:18458 .
The process applied in this research is presented on Figure 1. First step is the identification of biological models
in the literature and arbitrarily selecting the ones that can potentially generate architectural concepts with high
potential (step 1, part 2.1). These biological models are characterized and described using engineer and
architect-oriented criteria (step 2, part 2.2), and stored in a database that designers can explore and
comprehend (step 3, part 0).
This database can then be exploited to abstract models of their choice into more general concepts (step 4,
part 2.4). Foreseeing innovative designs applicable in their fields, technology and material considerations are
requested (step 5, part 2.4) before proposing a final concept of building envelope. The implementation of this
concept involves prototyping and evaluation (step 6, part 3) before potential integration on the market. Those
six steps are presented in the bottom part of Figure 1, in parallel to the ISO standard 2015:18458 . The
following sections detail, under the prism of the morpho butterfly biological model, steps 1 to 6 which led to an
actual bioinspired concept of adaptive building envelope.
Figure 1: Comparison of the solution-driven biomimetic design process (adapted from ) and the process
developed by the authors. Note that there may be iterations between steps 4, 5, and 6.
2.1 Pre-selection of biological models: biological envelopes (step 1)
Living organisms present a wide variety of behavioural and physiological characteristics. Such a diversity of
functions and systems cannot be taken into account all at the same time if one wants to get an overview of
models from different orders and even reigns. To narrow down the study perimeter of biological models, only
biological interfaces (integuments such as skin, membrane, feathers) are considered. As building envelopes,
all living organisms with integuments present wide ranges of living environments, as well as requirements to
survive (pressure, temperature, pH, light, oxygen levels, etc.).
Few species were selected (sample in Table 1) according to the following criteria:
- The environment of the species and their requirements for survival are similar to the ones expected
for a building. For example, deep sea species tolerating very high pressure were not considered as
- A biological envelope is usually composed by one to several layers, the outer layers being associated
to appendages: hair, scales, feathers, shells, etc. These features all provide diverse regulation
capabilities, hence the selection should represent a variety of these layers and appendages, in order
to propose to the candidates a large panel of functions.
Table 1: Some of the selected species with their respective layers and appendages.
Class / Order
Insect / Lepidoptera
Reptile / Squamata
Gastropod / Stylommatophora
Skin & mucous
Mammal / Primate
Insect / Hymenoptera
Pinopsida / Pinales
2.2 Engineer-oriented characterization (step 2)
The objective of characterizing the biological envelopes is to provide qualitative or quantitative description on
how they regulate some physical factors from the environment, and how they operate. The inputs from the
environment can be defined by:
- Abiotic factors , which are non-living chemical and physical elements of the environment that affect
living organisms. Typically, rain, ambient air or wind, are abiotic factors which can affect the internal
temperature of a living organism.
- Biotic factors , which are living organisms affecting their environment. For a biological envelope, it
could be the influence of other species, whether it is mutualism or predation, or the influence of the
species themselves, through behaviour mechanisms or metabolism.
Based on previous work on physical biological envelopes , , the authors proposed a characterization
of biological envelopes through regulations factors relative to building envelope requirements (thermal comfort,
heat regulation, load resistance, etc.) described by physical factors and features. The characterization of the
morpho butterfly is shown in Table 2, even though it was applied to all selected species. It is specified for each
regulation property whether it is caused by biotic factors, abiotic factors, or both: thereby, users of this
characterization can grasp the underlying physical phenomena of functions while taking into consideration
their mechanisms of activation.
Table 2: Characterisation parameters applied to the wings (thorax) of the morpho butterfly. A: Abiotic factor,
B: biotic factor. No particular characteristics were found in the literature about air and sound properties of the
Structural blue colour for iridescence with
Honeycomb-like structure 
Orientation of wings 
Surface properties different top/bottom
Orientation of wings for long-wave radiation
towards sky or near environment 
Haemolymph circulation for heat dissipation
Wings shuffling for forced convection 
Higher emission in near infrared when
Hydrophobic surface from nano-structuration
Self-cleaning surface 
Flexible and ductal material, multi-structuration
2.3 Data exploration for concept generation (step 3)
The characterized biological principles were then tested as bioinspiration sources for architectural purposes
during a two-session workshop. The experiment was conducted with 10 participants: 3 architects, 4 engineers,
and 3 mixed profiles (architect-engineers). The protocol was the following:
- Training-course on bioinspiration and application in architecture;
- Presentation of the characterized database, then exploration and abstraction by the participants with
the instruction to derive one or several envelope designs. The proposed designs have to preferentially
comply with a Cfb climate  and ideally regulate multiple functions of their choice;
- Restitution of the concepts: live sketches, and transposition of concept to systems or products of
In addition to the characterization in Table 2, decision-support tools were provided to designer to help meta
exploration, and facilitate a first sorting of few biological models.
Table 3: Qualitative characterization of regulation factors of the wings of morpho butterfly. A quick glance on
the radar chart indicates a combination of interesting properties in regards with light, air and heat regulations
as well as structural properties.
Visual tool (Kiviat)
Meaning of score
0 to 3: None to high involvement of the
biological envelope (intrinsic properties)
in the regulation of abiotic factors.
For water regulation, the cuticule is watertight
and the scales have hydrophobic properties
0 to 3: None to high impact of biotic
factors on the regulation of abiotic
For heat regulation, the species orients or
flaps its wings (Heat=2), for heat radiation
with environement or forced air convection.
2.4 Abstraction and transposition of biological models (steps 4 and 5)
Abstraction is an inductive process leading to underlying functional principles of biological systems . At this
stage of the design process, Abstraction level and Dimension ratio criteria were introduced to participants of
- Low to high abstraction level is related to the degree of contextualisation of a biological model. The
physical context of a biological model can be described under various scales, whether it is considered
as a system, a sub-system or a super-system. In this definition, low abstraction means detailing a
biological model under one scale only, whereas high abstraction is considering different scales
combined to result in one to multiple functions.
- Dimension ratio is comparing the spatial scale(s) of a specific abstraction of a model, to a technologic
transposition of this same model (Error! Reference source not found.).
When the designers questioned themselves whether the transpositions were to be seriously considered as
viable concepts, these criteria helped them explore technological alternatives. Zooming in and out of the
biological models and their transpositions offered new viewpoints, thus facilitating technological transfer and
Table 4: Transposed thermoregulation principles to potential technologies. Dimension ratio: abstraction
dimension / transposition dimension, such as nano (n), meso (m), macro (M).
Abstraction for heat
Intrinsic emissive properties of
scales on wings adapting on a
given temperature range due to
nano-structuration of scales on
Direct use of a scale-like material
Changing-texture nano materials
Interchangeable materials for each
Enhancing convection with
wings while flying
Moving surfaces for convection
Involvement of users in envelope
Orienting wings towards various
environments for heat radiation
Changing surface orientation (sky,
For instance, the wings of the morpho have intrinsic hierarchical properties, providing adaptive thermal
protection (see Figure 2). An example of a low abstraction would be using similarly nano-structured material
without an overview of the wing architecture and their multiple scales patterns. The direct transposition to a
technology would most certainly require nano-printing chitin-like material. Although crustacean polymers have
already been manipulated in additive printing research and have shown promising properties , the scale-
up to a building seems rather ambitious in terms of cost and more importantly energy-use. An example of a
higher abstraction would be to combine solutions at different scales, such as manually interchanging materials
(macro) that have different emissive properties (nano).
Figure 2: a) Morpho species photography, Credit: Pixabay Licence. b) From left to right, optical images of the
scales on the wing surface, of the butterfly wing scale and of a transverse section of the scale showing
ridges with lamella structures. Credit: Adapted from , Licence CC BY-NC 3.0.
3. Emerged concept: bioinspired adaptive skin (step 6)
From the various abstractions and transpositions of the morpho butterfly model, the following principles
emerged from the workshop:
- Adaptive smart-coating on the envelope for thermal regulation;
- Movable mesh changing the orientation of multiple surfaces for thermal and light regulations;
- Surface openings created by mesh distortion for thermal and air regulations;
- Partial control given to the building users to keep a human behavioural component in the design.
Combining these principles led to a final envelope concept, managing heat and light transfers into the building:
a skin envelope that has adaptive radiative, thermal, and light properties, depending on the geometrical
configurations set by the occupants.
3.1 Operating principle of the envelope Stegos
The envelope concept that was called Stegos is a deformable network of small opaque flat hexagonal metallic
elements (Figure 3) bonded by an elastic mesh. By stretching the mesh towards one side or the other of the
surface envelope, the elements are pulled apart: it lets light and air go through these newly-created apertures
modifying the overall behaviour to external weather conditions (sun, air, rain, etc.).
The Stegos is represented in a flat position and in a deployed position on Figure 3. The deformation
represented was generated with one tension point only, on the centre of the surface. Users of the building
control the distortion by choosing the location(s) and force(s) of the deformation(s) to regulate light and air
transmissions. To help distort the envelope, a wired or hydraulic system is to be defined.
Figure 3: Flat (a) and deformed (b) morpho butterfly-inspired envelope.
The hexagonal unitary elements are made of two layers; a fixed base and a rotating flap (Figure 4). When the
elements are pushed away from each other by the deformation, each of them operates a crank-handle initiating
individual and graduated rotations of the flaps. The deformation of the mesh is the highest near the tension
point; the closer to this point, the further the elements are moved apart. Therefore, the rotation of the flaps can
be controlled by the chosen intensity of the applied force by the user, and its location as well.
3.2 Adaptive absorption coefficient
An additional functionality is achieved through a coating on the external surface of the unitary elements, i.e.,
on top of the flaps, that provides an auto-reactive behaviour. A thermochromic smart-paint is formulated to
change when reaching a specific temperature: from one colour to a lighter one, the absorption coefficient of
the surface significantly decreases in the visible spectrum. As it accounts for about 55% of the total solar
spectrum energy , the surface temperature of the flaps is predicted to rise slower when exceeding the
Figure 4: a) Representation of the kinetics of the elements when the design is flat or deformed. b) Colour
change when heated above a threshold temperature. The sample was coated with an OliKrom paint ,
formulated in accordance to the authors specifications.
This concept can be designed to be integrated as the full envelope itself, aiming as a regulating adaptive
separator between the inside and outside environments. Despite its radical rupture with traditional and
popularly accepted rigid envelopes designs, it can offer interesting regulation assets for warm climates: when
flat, the smart-painting auto-reacts in accordance to the surface temperature, hence protecting the envelope
from overheating. When deformed, it acts as an opened window, letting air and light penetrate the interior
space as intended by the user, while ensuring auto-shading of the envelope. In case of humid climate, one
could also imagine using the flaps as rain-water collector or guiders towards storage units or evaporative-
Other options would be to position the design either in front of windows as a smart shading-device, or in front
of walls, coupled with a screen frame to act as a second skin. Compared to common second skins found in
the market of buildings, the adaptive emissivity of the external surface would be thermally beneficial. Moreover,
possible convection induced by the openings when deformed might also add a beneficial additional thermal
feature for the design.
4. Discussion and future work
This paper presents a new experimental framework derived from  for the design of bioinspired building
envelope through the case-study of the morpho butterfly.
The characterization of the preselected models of biological envelopes helped designers explore, abstract,
and transpose biological data into simple to complex bioinspired concepts. The example of the morpho butterfly
led to an interesting design of a bioinspired skin managing multiple regulating functions. The key features that
inspired the emerged design are the morpho wings adaptive radiative properties and the animal behavioural
mechanisms. The abiotic criteria defined for this framework helped underline intrinsic properties of the animal
wings, that happen to have a strong dominance on the final proposed bioinspired design. Yet, biotic criteria,
identified as wings flapping or varying orientation, clearly provided ideas on the configuration sets (deformation
coupled with orienting flaps) of the envelope. It also added a strong behavioural component to the global
morpho model, that transposed in the design through controlled deformations by the building user.
The proposed design gathers multiple features: deformation of surface, deployment of elements, and surfaces
with adaptive emissivity. To measure the benefits of all features combined in terms of heat, light, and air
transfers, the design is currently being prototyped and tested in real conditions following two main stages. First
measurements will be carried out for the design configured as a smart and flat shading device installed on a
hot box as seen in Error! Reference source not found. (a), to enhance thermal, radiative and self-shadowed
Figure 5: a) Configuration of the prototype integrated to a 1m-side cubic test box. b) Photos of the equipped
test box. c) Zoom on flaps with shades of blue due to differences of temperatures.
Second, tests will be performed on a deformable direct interface version to assess light projections and air
flows generated by various deformation configurations. In parallel, evaluation of these designs through
modelling should bring insight on these first measurements and guide the next ones.
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