Mechanisms of Heat Transfer in Human Body and Heat Loss in Uninsulated Brick Veneer House

SOLUTIONS TO THE QUESTIONS
QN 1: The ways that the human body gains or losses heat to its environment and explanation
how these mechanisms work:
ANSWER:
The following are the ways in which the human body either gains or losses heat (depending on
the environment)
Normally if too cold, the body will want to gain heat and more heat from the surrounding and
when too hot, the body will want to lose more heat so as to cool the body.
(i) Radiation
This is the mode of heat transfer in which the body either gains or losses heat to the
surrounding.
(ii) Evaporation
This is facilitated by sweating in hot and humid weather such that the liquid (sweat)
on the skin turns to vapor hence causing a cooling effect on the body.
(iii) Convection
This is the process in which air currents flow over the skin and with it takes away
some heat from the body surface. By moving around, the rate of heat loss through
convection increases.
(iv) Conduction
This is such that whatever the body is in direct contact, it either loses or gains heat.
For instance, in the figure below, the person is seated on a stone hence heat from
his body is lost to the stone via conduction. Sitting establishes direct contact of the
body with the stone.

QN 2: For an uninsulated brick veneer house in Sydney in winter, description of the main paths
of heat loss to the outside air
ANSWER:
The house loses heat from different paths from the interior. Mainly the major losses are
realized via the openings such as doors, windows and roofs as shown in the diagram. The
arrows show the direction of heat loss.

QN 3: Calculation of the thermal conductance (U value) across a cavity wall consisting of:
 Outer skin 110mm brickwork (South facing, exposed aspect
 30mm cavity
 Inner skin of 90mm studwork with 10mm plasterboard
ANSWER:
.
Discuss whether or not cavity brickwork is a thermally efficient wall for housing in Australia.
Inner skin
Studwork material
c
a
v
i
t
y
Outer skin
Brickwork
material