Heat: Ways the Human Body Gains or Loses Heat to its Environment

This assignment explores the ways in which the human body gains or loses heat to its environment. It discusses the mechanisms of heat loss through evaporation, conduction, radiation, and convection. It also examines the main paths of heat loss in an uninsulated brick veneer house in Sydney during winter. Additionally, it covers the calculation of thermal conductance across a cavity wall and discusses the thermally efficiency of cavity brickwork in housing in Australia. Finally, it describes five strategies for passive solar cooling in hot dry climates and how angled louver blades can be designed to manage the entry of direct sunlight into a building in a location like Sydney.

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ASSIGNMENT 2 – HEAT
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With diagrams describe the ways that the human body gains or loses heat to its
environment. Explain how these mechanisms work.
Living beings’ bodies always produce heat through metabolic processes. Heat output is 100W
but can reduce to 70W when one is asleep and rise to 700W when working. The heat should
always emit the heat out to avoid death. The body’s thermal-regulation is very useful (Houdas &
Ring, 2013).
E – Evaporation
Rd – radiation
Cd – Condensation
Cv - Convection
The human body gains or losses heat through the above named processes.
Heat loss through evaporation
During hot weather conditions, the cells of the skin push water to the skin surface so that the
body heat can evaporate it thus cooling it.
Heat Gain or loss through Conduction
When the body comes into contact with a warm object it takes in the energy and when one
touches a cold object heat moves from the body to the object (Gusheh & Lassen, 2017).
Heat lost through Radiation
Transfer of heat happens via electromagnet waves.
Heat lost through Convection.
There is always layer of warm air around our bodies and wearing warm clothes normally traps it.
Exposure to wind will blow away the warm layer thus leaving the body with cold layer making

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the body loose heat (Gusheh & Lassen, 2017). A human body must either loose or gain heat to
achieve the required level of human comfort.
2. For an uninsulated brick veneer house in Sydney in winter describe the main paths of
heat loss to the outside air
Just like human beings, buildings loose heat to the surrounding and also gain from it. Heat will
mostly be lost through; the ceiling, walls, glazing, floor and through ventilation holes. The
uninsulated brick house in Sydney will lose about 35% through walls, 25% through the roof and
40% through windows, ventilation holes and the floor (Houdas & Ring, 2013).
Heat loss due to Surface to Volume ratio
A big building has a small surface to volume ratio hence likely to lose a lot of heat whereas a
smaller building would behave oppositely due to a higher ratio.
Heat loss through Windows
Windows easily lose heat due to them having a low thermal mass. To minimize such losses the
window area should be minimized. If large windows are necessary then they should be double
glazed with low e-treatment and have partly evacuated with inert gas fill.
Heat loss through Walls
This will happen due to the lack of insulation. Insulation can be enhanced by putting cavities
between studs of the wall frame making part of the brick veneer (Law & Dewsbury, 2018). An
air gap should also be in between the sheathing and brick veneer to ensure insulation.

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Heat loss through Ventilation
Hourly air changes should be kept at a minimum of 0.5 and all entry points should have an air
lock (Law & Dewsbury, 2018). The building should generally be airtight to reduce heat escape.
Q3. Do a quick calculation of the thermal conductance (U value) across a cavity wall
consisting of:
X Outer skin 110mm brickwork
X 30mm cavity
X Inner skin of 90mm studwork with 10mm plasterboard
U value = 1/ Thermal resistance (R)
Thermal conductivity
Outer skin = 0.6
Inner skin = 0.6
Plaster = 0.5
R= Thermal conductivity/Thickness of material
110/0.6 = 183
90/0.6 = 150
10 / 0.2 = 50
1/1.83 = 0.546
1/1.50 = 0.667

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1/0.50 = 2
U = 1/R1 + 1/R2 ….
0.546 + 0.667 + 2 = 3.213Wm2K
Discuss whether or not cavity brickwork is a thermally efficient wall for housing in
Australia.
Brick has the capacity of making energy efficient houses since it can hold energy that gets into
the house on a sunny day and slowly emit it in the night thus having an advantage over most
lightweight materials (Aldawi, et al., 2013). Upon cladding with cavity, it forms a perfect
comfortable house for the extreme temperature changes of Australia. This combination ensures
mechanical and thermal heating are kept at a minimum. Cavity brickwork can make energy
efficient units that ensure less energy is used when heating or cooling houses in the winter and
summer respectively (Soebarto & Bennetts, 2015). Combining the cavity brick properties with
passive design strategies will result in an optimum thermally efficient unit in Australia.
Q4. Describe five strategies for passive solar cooling in hot dry climates
Louver shading devices
They should be positioned in facades along the sun path to block direct sun rays. They should be
fixed at 450 to ensure rays are blocked and light is allowed to penetrate (Soflaei, et al., 2016).

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Double glazing
Heat gains and losses majorly occur through the windows and thus insulating the windows can
minimize the effects of solar radiation (Soebarto & Bennetts, 2015). The space created after
double glazing can be filled by a vacuum or inert gas to discourage heat transfer due to reduced
solar heat gain coefficient.
Green Roofing
Having green plants at the roof will produce oxygen which helps creating a heat island effect in
the urban environment thus reducing air temperature.
Insulation
This will act as an obstacle for heat transfer thus ensuring thermal comfort in the house.
Insulation should be done in the areas where heat lose is likely to occur.
Use of light color coatings
This will reflect away heat and ensure the building indoor temperature is manageable and
comfortable (Thorpe, 2010). Light coating with high reflective property can be used to minimize
solar heat gain.
Q5. Describe how angled louver blades can be designed to manage the entry of direct
sunlight into a building in a location like Sydney
The louvers can absorb, obstruct, transmit and reflect solar radiations to the interior spaces of a
building. Their performance relies on their position, sun position, slate angle and reflective
properties (Szokolay, 2008). Slates that have been tilted upwards transmit light from sun while
those that have been tilted downwards transmit light from the ground (Soebarto & Bennetts,
2015). Even day light transmission is made possible by the louvers when the sky is over cast.

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Louvers can be made to be flexible in that it is possible to regulate the amount of sunlight to a
desired limit. Operable and fixed louvers can be used to control thermal gains, protection against
glare and redirected light (Gusheh & Lassen, 2017).

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References
Aldawi, F., Date, A., Alam, F., Khan, I. and Alghamdi, M., 2013. Energy efficient residential
house wall system. Applied Thermal Engineering, 58(1-2), pp.400-410.
Chandrashekaran, D., 2010. Air flow through louvered openings: Effect of louver slats on air
movement inside a space. University of Southern California.
Dabaieh, M., Wanas, O., Hegazy, M.A. and Johansson, E., 2015. Reducing cooling demands in a
hot dry climate: A simulation study for non-insulated passive cool roof thermal performance in
residential buildings. Energy and Buildings, 89, pp.142-152.
Gusheh, M. and Lassen, C., 2017. Marie Short House: Glenn Murcutt. Companion to the History
of Architecture, pp.1-10.
Houdas, Y. and Ring, E.F.J., 2013. Human body temperature: its measurement and regulation.
Springer Science & Business Media.
Law, T. and Dewsbury, M., 2018. The Unintended Consequence of Building Sustainably in
Australia. In Sustainable Development Research in the Asia-Pacific Region (pp. 525-547).
Springer, Cham.
Thorpe, M., 2010. Brickwork Level 3. 3rd ed. Abingdon, United Kingdom: Routledge.
Sherwood, L., 2015. Human physiology: from cells to systems. 2nd ed. Boston, United States:
Cengage learning.
Soflaei, F., Shokouhian, M. and Shemirani, S.M.M., 2016. Investigation of Iranian traditional
courtyard as passive cooling strategy (a field study on BS climate). International Journal of
Sustainable Built Environment, 5(1), pp.99-113.
Szokolay, S.V., 2008. Introduction to architectural science: the basis of sustainable
design/Steven V. Szokolay.
Soebarto, V. and Bennetts, H., 2014. Thermal comfort and occupant responses during summer in
a low to middle income housing development in South Australia. Building and environment, 75,
pp.19-29.

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