A brief on what is thermoregulation and how it manifests in nature in hot and humid climates in various plants and animals.

1. THERMOREGULATION IN
HOT AND HUMID CLIMATES
Part I
ANOUSHKA PRANATI PRIYANKA S BALA
GROUP 12

2. WHAT IS THERMOREGULATION ?
Thermoregulation is the ability of an organism to keep its body temperature within certain
boundaries, even when the surrounding temperature is very different.
A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its
own body temperature, thus avoiding the need for internal thermoregulation.
The internal thermoregulation process is one aspect of homeostasis: a state of dynamic
stability in an organism's internal conditions, maintained far from thermal equilibrium with its
environment.
Thermoregulation in organisms runs along a spectrum from endothermy to ectothermy.
• Endotherms create most of their heat via metabolic processes and are colloquially
referred to as warm-blooded. When the surrounding temperatures are cold, endotherms
increase metabolic heat production to keep their body temperature constant, thus making
the internal body temperature of an endotherm independent of the temperature of the
environment. One metabolic activity, in terms of generating heat, that endotherms can do
is that they possess a larger number of mitochondria per cell than ectotherms, enabling
them to generate more heat by increasing the rate at which they metabolize fats and
sugars.
• Ectotherms use external sources of temperature to regulate their body temperatures. They
are colloquially referred to as cold-blooded even though body temperatures often stay
within the same temperature ranges as warm-blooded animals. Ectotherms are the
opposite of endotherms when it comes to regulating internal temperatures. In ectotherms,
the internal physiological sources of heat are of negligible importance; the biggest factor
that enables them to maintain adequate body temperatures is due to environmental
influences. Living in areas that maintain a constant temperature throughout the year, like
the tropics or the ocean, has enabled ectotherms to develop a wide range of behavioral
mechanisms that enable them to respond to external temperatures, such as sun-bathing to
increase body temperature, or seeking the cover of shade to lower body temperature.

3. HOT AND HUMID CLIMATE
Places with hot and humid climate throughout the
year exist in various parts of the world. The
building design requires clear criteria to avoid
overcooling and energy wastage, at the same time
that guarantee optimal thermal comfort conditions
delivered to its occupants. In this scenario,
bioclimatic strategies such as the use of natural
ventilation and shading, as well as the choice of
appropriate construction components, are decisive
to reduce the building energy consumption and the
heat island effect. Designer decisions are
fundamental in the future performance of the
building. Therefore, it is very important to know the
special characteristics of climates and microclimates
around the building to properly to choose the best
choice during the design process. In regions of hot
and humid climate, the adoption of passive
strategies and design that encourage the occupants’
adaptation to local temperature variations is
essential to achieve thermal comfort in different
ways, as is the deep understanding of its
implications as an inducer of design guidelines for
both residential and commercial buildings.

4. THERMOREGULATION IN NATURE
Living organisms must maintain their
body temperature in a very narrow
range in order to survive. They can
manipulate it by behavioral or
physiological manners. In addition to
generating heat metabolically,
organisms exchange heat with their
surroundings by:
• Conduction
• Convection
• Evaporation
• thermal radiation
Maintaining a stable body temperature
is achieved by a continuous process of
heat gain and loss. A wide range of
strategies are adapted to facilitate
heat gains and losses by organisms. In
some organisms, the process is achieved
through the skin which functions as a
thermal filter, whereas in others, it is
achieved by their built structures.
Different mechanisms are adapted for
different climates and for different
species.

5. In the heat
In environment where the ambient temperature is higher than body
temperature, the body receives heat by conduction from the hot air, by
radiation from sun, and by the heated ground surface. Evaporation is
often used by mammals to dissipate the metabolic heat production
and the heat gained from the environment.
• The importance of body size – since heat gain of an object by
conduction, convection and radiation processes has a direct
relation to surfaces; the sum of environmental heat load on an
object is directly related to surface area. A small animal loses
heat to the surroundings rapidly and can not maintain his body
temperature very different from the medium.
• Evaporation- sweating, panting, and gular fluttering – these
processes are basically adapted to increase cooling by
evaporation. When air flows over a moist surface it causes
evaporation, which in turn takes a certain amount of heat from the
surface. Sweating, panting, and gular fluttering are mechanisms
that occur in different species. The capability of sweating is found
in some mammals including humans, horses, camels, and some
kangaroos. However, birds do not sweat, that is why they have
adopted gular fluttering which occurs in their mouth – they keep
their mouth open and vibrate the floor of the mouth (gular area)
to increase the airflow and as a result promote evaporation.
Panting is common among birds and mammals, where the rate of
breathing is increased as a result of heat stress, e.g. dogs

6. THERMOREGULATION OF PLANTS
Boundary layer – The boundary layer is a thin layer of still air
hugging the surface of the leaf. This layer of air is not moving.
For transpiration to occur, water vapor leaving the stomata
must diffuse through this motionless layer to reach the
atmosphere where the water vapor will be removed by moving
air. The larger the boundary layer, the slower the rates of
transpiration.
Plants can alter the size of their boundary layers around leaves
through a variety of structural features. Leaves that possess
many hairs or pubescence will have larger boundary layers;
the hairs serve as mini-wind breaks by increasing the layer of
still air around the leaf surface and slowing transpiration rates.
Some plants possess stomata that are sunken into the leaf
surface, dramatically increasing the boundary layer and
slowing transpiration. Boundary layers increase as leaf size
increases, reducing rates of transpiration as well. For example,
plants from desert climates often have small leaves so that their
small boundary layers will help cool the leaf with higher rates
of transpiration.

7. SUNFLOWERS
The property of facing the sun is mostly observed in young flowerheads
and generally stops once the flower starts to bloom (mature sunflowers
generally face east). The fascinating phenomenon of flowers following the
sun across the sky is called heliotropism.
Plants are known to synchronize themselves with the light in their
surroundings. This is known as the Circadian rhythm. They are generated
by the plants themselves and are self-sustaining. There are different ways
of how the plants carry it out and how they show it as well. Sunflower has
its own way and that way is using a certain hormone.
Plants are known to synchronize themselves with the light in their
surroundings. This is known as the Circadian rhythm. They are generated
by the plants themselves and are self-sustaining. There are different ways
of how the plants carry it out and how they show it as well. Sunflower has
its own way and that way is using a certain hormone.
Each sunflower plant has only one flower on its stem. Therefore, during
pollination, it is essential that the plant’s only means of reproducing gets
noticed by pollinators (mainly insects). Continuously, facing towards east
also helps the flowers to heat up quickly. This gives them an advantage in
pollination as warm flowers attract insects. Therefore, it’s in the plant’s
best interest that the flower always faces the Sun, so it is always highly
visible to these important pollinators.
Mature sunflowers finally stop displaying heliotropism when they start to
develop seeds and therefore droop from the weight of these seeds. They
end up mostly facing east from this point in their lifecycle.

8. Viscoelastic matrix ( cutin ) of plant cuticle
protects fruit from cracking by fibrillar
components capable of passive realignment
when placed in tension.
Plant cuticles play a key role in a plant's interaction with the
environment and in controlling organ expansion because "the lipid
cuticle layer is deposited on the surface of outer epidermal cell walls
and modifies the chemical and mechanical nature of these cell walls"
(Domíngueza et al. 2011: 77). The cuticle is made up of
polysaccharides and flavenoids that contribute to the nature of its
stiffness. Compared to the rest of the epidermal cells, the cuticle is
much less flexible. Harder cuticles help protect against fungal
pathogens more efficiently than softer ones. Stiffness can be
modulated by a plant's ability to realign its fibrils in the direction of
an applied force. In other words, plants better at opposing the force
through their fibril alignment are able to maintain their stiffness under
stress.
The properties of cuticles (that is their stiffness and strength) can be
altered by temperature and humidity. For example, fruit tends to go
bad more often when kept out in the heat because the cuticle
becomes degraded thus allowing external factors to penetrate its
surface. Understanding the mechanical properties of the cuticle could
lead to fruits that last longer on the shelves and better withstand
attack from animal and fungal pests.

9. The scales of pine cones flex passively in response to
changes in moisture levels via a two-layered structure.
“The mechanism of bending therefore seems to depend on the way that the
orientation of cellulose microfibrils controls the hygroscopic expansion of the cells in
the two layers. In sclerids, the microfibrils are wound around the cell (high winding
angle) allowing it to elongate when damp. Fibres have the microfibrils orientated
along the cell (low winding angle) which resists elongation. The ovuliferous scale
therefore functions as a bilayer similar to a bimetallic strip, but responding to
humidity instead of heat.”

10. Stoma brick
In this section we present an application of the taxonomy methodology for
arid and dry climates. An evaporative cooling system (Stoma Brick - SB) for
building envelopes (fig. 1) was designed based on principles (Table 2) of
several natural systems. These include stoma of a plant, pine cones, hair
protecting eyes in the desert, and human skin.
The system consists of four integrated parts (fig. 2):
1. The Stoma brick – SB (fig. 4): made of porous material, which is the
functional part for thermoregulation. It has an outer layer of hairy structure
to filter the air passing through the envelope. A veneer shutter to control
opening/closing in accordance to humidity gradient. The most inner layer is
spongy to hold moisture for evaporation.
2. The mono-brick: it includes an irrigation cycle that irrigates through holes
the SBs, which are inserted into the mono-brick to allow a continuous
performance vertically. Two configurations of mono-bricks exist for this
envelope, 3 SBs and 9 SBs, depend on their position in
the specific envelope design.
3. The steal framing: is the load bearing structure of the cooling system.
4. The inner layer: HEPA filter for air cleaning or a double acrylic glass for
lightening and visual contact with the exterior environment.

11. Mound facilitates gas exchange
The structure of above-ground macrotermite mounds facilitates gas exchange in the below-ground
nest using internal air currents driven by solar heat.
Mound-building macrotermites construct vertical mounds out of soil, saliva, and dung. They mounds
generally resemble chimneys, with some mounds having large vents while others have porous walls.
Inside these mounds, worker termites can dig a complex array of tunnels of various sizes. The
termites themselves live in nests below ground in colonies that can contain up to a million individuals.
The most recent published research suggests that the mounds function much like mammalian lungs
and act as accessory organs for gas exchange in the underground nests. It was previously thought
that termite mounds functioned to continuously maintain the nest’s internal temperature within a
narrow range in the face of extreme outside temperature fluctuations, but research on mound-
building termites like Macrotermes michaelseni is expanding our understanding of mound function.
During the day, changes in internal nest temperature are less extreme than changes in outside
temperature, but over the course of a year, nest temperature does vary and closely follows the
temperature of the surrounding soil. The soil has a large thermal capacity and acts as a “buffer”
against daily changes in outside temperature.
The main mechanism for gas exchange is through internal air currents driven by solar heat. As
outside temperatures change throughout the day and the sun strikes different surfaces on the
mound, temperature gradients develop between the mound periphery and center. These
temperature gradients create currents of rising and falling air inside the mound. The direction of
these currents varies as temperature gradients change throughout the day. Wind energy from
unsteady airflows outside the mound may also play a secondary role in ventilation. The internal
airflows llikely promote mixing between air in the mound and air in the nest, ultimately facilitating
gas exchange in the nest.
This growing understanding of macrotermite mound structure and function could inspire new
biomimetic technologies in energy-saving climate control systems.

12. BIOMIMETIC ARCHITECTURE: Green Building in Zimbabwe
Modeled After Termite Mounds
The Eastgate Centre is a shopping center and office building located in Harare,
Zimbabwe. Rather than using a traditional fuel-based air-conditioning system to regulate
temperature within the building, the Eastgate Centre is designed to exploit more passive
and energy-efficient mechanisms of climate control. The building’s construction materials
have a high thermal capacity, which enables it to store and release heat gained from the
surrounding environment. This process is facilitated by fans that operate on a cycle timed
to enhance heat storage during the warm daytime and heat release during the cool
nighttime. Internal heat generated by the building’s occupants and appliances also help to
drive airflow within the building’s large, internal open spaces, as it rises from offices and
shops on lower floors toward open rooftop chimneys. Various openings throughout the
building further enable passive internal airflow driven by outside winds. These design
features work together to reduce temperature changes within the building interior as
temperatures outside fluctuate. The $35 million building saved 10% on costs up-front by
not purchasing an air-conditioning system. Rents are less expensive in this building
compared to nearby buildings because of the savings in energy costs.
BIOMIMICRY STORY
In Harare’s climate, the purchase, installation, and maintenance of a traditional air-
conditioning system for a building has immediate and long-term costs. The challenge was
to create a self-regulating ventilation system that would keep the building at
temperatures that are comfortable for workers and residents. Architect Mick Pearce
worked with the construction company Arup to design the Eastgate Centre. Pearce was
inspired by models of internal temperature regulation in termite mounds. At the time of
the building’s design, researchers had proposed that termite mounds maintained stable
internal climates by having a physical structure that enables passive internal airflow.
While subsequent research on termite mounds has altered our understanding of the
function of mound structure, the Eastgate Centre still achieves a controlled internal climate
with the help of cost-effective and energy-efficient mechanisms originally inspired by
termite mounds.

14. Asymmetric burrow openings create passive
ventilation
Prairie dogs are highly social rodents that build extensive
underground burrows in the plains of North America to house their
family groups. The burrows can reach 10 m (32 ft) in length, and
this size means that diffusion alone is not sufficient to replace used
air inside the burrow with fresh air. The way that a prairie dog
builds the openings to its burrow, however, helps to harness wind
energy from the windy plains and create passive ventilation through
the burrow’s tunnels.
As air flows across a surface, a gradient in flow speed forms, where
air moves slower the closer it is to the surface. The prairie dog is
able to take advantage of this gradient by building a mound with
an elevated opening upwind and a mound with a lower opening
downwind. Over the elevated opening, wind velocity is faster than
it is over the lower opening, creating a local region of low pressure
(following Bernoulli’s principle). The result of this difference in
pressure between the two openings is one-way air flow through the
burrow as air gets sucked into the lower opening and flows out the
elevated one. This is the mechanism behind a Venturi tube.
The mounds around the burrow openings serve additional functions
for the prairie dog, like providing a perch to watch for predators.
Other organisms use a similar arrangement of openings to generate
passive flow, including sea sponges and limpets.

15. VIETCONG TUNNELS

17. Heat Exchange from the Toucan
Bill Reveals a Controllable
Vascular Thermal Radiator
Glenn J. Tattersall1,3,
Denis V. Andrade2,3,
Augusto S. Abe2,3
Science 24 Jul 2009:
Vol. 325, Issue 5939, pp. 468-470
“Toucans are instantly recognizable by their
large bills, which in the toco toucan (Ramphastos
toco) accounts for about one-third of the total
body length. The toucan's bill has been
interpreted as a sexual ornament and as an
adaptation for handling fruit. Tattersall et
al. (p. 468) explore an alternative explanation in
which the bill serves primarily as a
thermoregulator. Infrared thermography
techniques, which allow detailed observations
with minimal disturbance to the birds, show that
the birds alter blood flow to the bill according to
ambient conditions, effectively using it as a
radiator to ‘dump heat.’ “

18. Temperature profiles of surface temperature differentials of
the toucan bill at four different Ta (15°, 20°, 20°, and 35°C).
The lefthand plots depict the average Tsurf – Ta differences for
adults (n = 4, black circles) and juveniles (n = 2, gray circles),
expressed against the relative distance along the bill (white
line in top middle panel; 0 = proximal end; 100 = distal tip).
The middle column depicts thermographic images from adult
(a) and juvenile (j) toucans at the respective Ta.
The ratio of the juvenile:adult values for the Tsurf –
Ta differences is shown in the righthand panels. The horizontal
dotted line indicates the line of equality, where the ratio = 1.

19. Architecture inspired by Nature
A Hotel designed with Biomimicry, inspired by praire dogs for ventilation
system, toucan peak for thermal exchange and cactus for self-shading
The Votu Hotel was designed to achieve high performance on thermal
comfort. It is located at Bahia, Brazil with an annual temperature average of
750F and high humidity rate. The project was developed using Biomimicry.
The bungalows have constant air renovation inspired on prairie dog, whose
caves are below ground with airflow system following Bernoulli Principle. The
design created a barrier to decrease the airflow velocity with the guardrail
adjacent to the concrete structure that has the ventilation holes. The air
continuous to flow through the tubes inside this structure and exits freely
throughout the louvers on the top of the wall.
The bungalow shell was inspired on Saguaro cactus performing self-shading
structures.
The kitchen roof was inspired on toucan peak to exchange heat. Inspired on
this thermal radiator system, the kitchen roof exchanges heat within a layer
of soil shaded by a roof garden in a capillary cooper pipe system with
mechanical air flow.