University of Western Sydney - Light, Heat, and Sound Assignment 1

This assignment explores the fundamental concepts of light, heat, and sound, crucial elements in environmental engineering. It begins by examining the human eye's photoreceptors (rods and cones) and their impact on vision and lighting design, followed by an analysis of factors influencing workplace lighting levels, including visual safety, accuracy, and cost. The assignment delves into the factors affecting natural light, such as window size, shading, and building articulation. It then transitions to heat, discussing human body temperature regulation, heat gain, and loss mechanisms, as well as the role of thermal mass and insulation in building design. Finally, it covers sound, exploring noise reduction techniques through wall design, structure-borne sound mitigation, and the control of reverberation time in acoustic environments. The solution utilizes diagrams and references to provide a comprehensive understanding of these interconnected topics.

ASSIGNMENT 1 – LIGHT, HEAT, AND SOUND
Light
1. The primary function of the human eye is for vision, but most of the core work is done
by the photoreceptors found in the retina – receive light and convert into signals. The
photoreceptors are rods and cones; rods are responsible for scotopic vision – vision under low
levels of light while cones are responsible for photopic vision – vision under high levels of
light (Sjöstrand, 2013, p. 42). The levels of light where both rods and cones work together are
known as mesopic vision. The photoreceptors adapt differently to their functions with
different features. These different features bring about the visions a human eye experience.
The rods are more sensitive than cones. The sensitivity of rods is contributed by the
numerous numbers they have. Rods are approximately 120 million in number making them
more sensitive with short wavelengths, whereas cones are about 5 million. The rods have a
slow adaptation to darkness (about 30 minutes) since they are numerous, while cones adapt
faster to daylight.
Cones contain iodopsin pigment, which is responsible for color vision as well as high visual
acuity level, whereas rods consist of rhodopsin responsible for night vision. The deficiency of
rhodopsin in the rods can lead to night blindness, while iodopsin deficiency in the cones can
lead to color blindness (Sjöstrand, 2013, p. 42). Cones are located at the center of the retina
while rods are located at the periphery around the retina
2.
Environmental concern; the amount of lighting to be used in a workplace should be
environmentally friendly.
Visual safety; the amount of light to be used in work should be suitable with distinguishable
colors to ensure visual efficiency. The occupants must be assured of their visual health.
Level of accuracy and perception – where a high level of accuracy, as well as fine detail
perception, is required, high lighting levels is used to ensure that quality work is delivered.
As shown in the figure below, such lights are recommended for theatre halls since fine detail
perception is not required (Preto & Gomes, 2018, pp. 180-191)

Coverage area; the area that the lighting will cover will determine the required light levels.
The bigger the area of lighting, the higher the amount of light required.
Cost; the cost of lighting should also be considered. The lighting of the workplace should be
economical in terms of energy-saving.
3. Lighting levels of a workplace are dependent on various factors, such as the nature of
tasks, perception of details, efficiency, and acuity.
Pathways for people and vehicles such as corridors, vehicle parks, etc.: The lighting level for
such pathways should be approximately 20 lux since the task being undertaken in this
situation does not require a large amount of light since not much acuity and efficiency are
required (Richman, 2015).
Hazardous pathways for people, machines, and vehicles such as excavation areas,
construction and clearance sites, soil work, and bottling require more lighting since the tasks
required no perception of details. The most recommended light levels for such areas are about
50 lux since some efficacy and acuity are essential (Richman, 2015). The hazardous areas
should be easily noticeable; hence average light levels should be required.
Tasks that require the limited perception of details do not demand more lighting. The
appropriate light levels for these tasks should be approximately 100 lux (Richman, 2015).
This lighting level is sufficient to avoid veiling reflections in areas such as factories and other
industries and kitchens.
On the other hand, tasks that demand fine perception of details require more lighting levels to
provide sufficient light for the task as well as ensure there are no stroboscopic effects in the
workplace. The recommended lighting level for such tasks is 500 lux in areas such as
electronic assembling factories, textile industries, and drawing offices (Richman, 2015).
Work that requires average detail perception is recommended with a lighting level of 200 lux.
Working-place that require such lighting including but not limited to, book-binding offices
and metal sheet industries.

4. Factors that affect the amount of natural light include;
• Amount of heat gain and loss, though it may sound ineffective, it is important to
consider heat loss and gain when installing a natural system of lighting. Considering
the installation of the skylights, roofing materials should not be insulated in order to
avoid thermal discomfort in the room since the amount of energy to be saved has
impacted on the lighting of the interior of the building
• Windows size and location and skylights; the location and size of the window
determines the amount of natural light illuminated inside the building. If the sill
height of the window is located above the eye line, the amount of daylight brightness
illuminated will be lesser. It is more appropriate to use top lights as opposed to large
windows since window enlargement comes along with other issues such as heating,
cold, flickers, and noise (Heydarian et al., 2016, pp. 212-223). The nature of the sky
also determines the amount of daylight; for instance, when cloudy, the amount of
natural light is less.
• Articulation of the building; the design and size of the building also has an impact on
the amount of daylight allowed inside. The side of the building with the window from
outside should be designed such that its width is less than 2.5 times the height of the
window. It is essential, therefore, to design the building with adequate and proper
location of windows for appropriate illumination.

 Shading plays an essential role in determining the amount of natural light falling on a
work surface in that they regulate the amount of direct sunlight that enters a building.
Case in point, buildings in the Southern hemisphere have the openings facing the
sunlight directly to allow more heat gain during the winter season. During the
summer, this is not the case; shading and louvering are required to prevent excessive
heat gain.
 Inside obstructions: the distribution of light in the building may be affected by inside
walls, large shelves, among other light obstructive objects. It is important, therefore,
to point out these objects when determining the design of the building to ensure that
adequate natural light is illuminated into the building.
Heat
5. The temperature of the human body changes depending on the temperate nature of the
environment. Human body temperatures are regulated through a fine balance between heat
loss and heat gain. The normal body temperature of a human being at rest is 36.5 to 37.5
Degrees Celsius (Houdas & Ring, 2013).
Heat gain
• External sources; the human body gains heat from external sources such as fire and sun.
• Digestion; during digestion of food, heat is produced that warms the body.
• Muscle activities; any movement in the body, resulting in heat production, which in turn
warms the body.
Heat loss
• Respiration; this involves inhaling and exhaling of gases. During exhaling, heat is lost
through breathing out of warm air.
• Conduction; when the body comes in contact with a cold surface (solids or liquids), heat
from the body is lost through conduction.

• Radiation; occurs through the emission of heat from the body.
• Evaporation; sweating removes excess heat from the body through evaporation.
• Convection; on windy days, heat from the body is removed by the moving water or air.
6. Brick veneer is an architectural method of construction where the structure has an
interior layer of either steel or wood frame that is concealed with an exterior mono-layer of
bricks. Bricks veneer houses in Sydney have a un-insulated airplane of about 25-50mm that
separates the frame and the bricks. Heat in a un-insulated brick veneer house can be lost
through walls, ceiling, and floor by the action of thermal mass. The heat loss can be through
modes such as conduction, radiation, and convection. Such heat loss can be minimized
through appropriate utilization of the thermal mall (Aldawi et al., 2013, pp. 403-418).
7. Thermal conductance (U value) = 1/Ri; where R is the addition of exterior and interior
surface and thermal resistance of each layer
110mm= (110/1000) m = 0.11m
30mm = 0.03m
10mm = 0.01m
R = thickness / thermal conductivity; brick = 0.77 W/k.m, cavity = 0.26 W/k.m
Plasterboard = 0.039 W/k.m
Ri = (0.11/0.77) + (0.03/0.26) + (0.01/0.039) = 0.51
U = 1/ Ri = 1/ 0.51 = 1.96

8. The difference between thermal mass and insulation is that thermal mass stores heat
during hot conditions and releases during cold conditions while insulation prevents the flow
of heat in and out of the building.
In terms of thermal performance, I do recommend lightweight construction in deserts such as
Alice Springs since they have low thermal mass. Desert temperatures fluctuate; hence low
thermal mass materials are appropriate to bring about thermal balance hence comfort in the
house (Al-Sanea, Zedan, & Al-Hussain, 2012, pp. 430-442).
Sound
9. Walls are the essential structural features that help in noise protection, both internally
and externally. Here are two ways that construction design solutions reduce noise;
• Use of cavity with increased airspace width; use of airspace can be between portions of
the wall and between two layers to reduce transmission of sound. The larger the width of the
airspace, the more the insulation of the sound though it is difficult to design (Kim & Park,
2018, pp. 545-549).
• Thickness and mass of the wall; the thicker the mass of the wall, the higher the resistance
of noise (Kim & Park, 2018, pp. 545-549). Insulation of sound is increased by increasing the
mass of the walls as shown in the figure below.
10. The term structure-borne sound means a sound that is transmitted through a building
structure. The sound results from vibration impact from the building fabric leading to
transmission of sound through a radiated surface (Cremer & Heckl, 2013). For example,
footsteps heard on the ground floor of a person walking on the upper floors.
To reduce structure-borne sound, carpets and pads, as well as resilient underlay, can be
applied on the floor to reduce sound vibrations.

11. Flanking sound is an indirectly transmitted sound. There are three pathways of
transmitting flanking sound. From the diagram of a building structure below, air-bone sound
can be transmitted through the floor, ceiling, and wall (Schoenwald, 2015, pp. 90-6814).
12. The acoustic
environment is an essential component of performance theatre for appropriate audio
perception (Rodosthenous, 2016, pp. 243-251). Figure 1 below shows damping, an essential
factor that ensures sound mitigation by reducing vibration on the walls and ceiling of a
theatre hall.
Drywall
Figure 2 below shows decoupling, a method that involves separating drywalls from studs to
avert sound transmission through the theatre.
Drywall
Drywall
Cavity

13. Reverberation time is the time the sound is expected to persist after it is produced in a
closed space. It is produced when a sound hits a surface such as a wall, floor, or ceiling and is
reflected. Sound reverberation can be reduced by designing surfaces with materials that
absorb sound (Schroeder, 2010, pp. 1187-1188).

Reference List
Aldawi, F., Alam, F., Date, A., Alghamdi, M. and Aldhawi, F., (2013). A new house wall
system for residential buildings. Energy and Buildings, 67, pp.403-418.
Al-Sanea, S.A., Zedan, M.F., and Al-Hussain, S.N., (2012). Effect of thermal mass on the
performance of insulated building walls and the concept of energy savings potential.
Applied Energy, 89(1), pp.430-442.
Cremer, L., and Heckl, M., (2013). Structure-borne sound: structural vibrations and sound
radiation at audio frequencies. Springer Science & Business Media.
Heydarian, A., Pantazis, E., Carneiro, J.P., Gerber, D. and Becerik-Gerber, B., (2016). Lights,
building, action: Impact of default lighting settings on occupant behaviour. Journal of
Environmental Psychology, 48, pp.212-223.
Houdas, Y. and Ring, E.F.J., (2013). Human body temperature: its measurement and
regulation. Springer Science & Business Media.
Kim, B.S. and Park, J., (2018). Double resonant porous structure backed by air cavity for low
frequency sound absorption improvement. Composite Structures, 183, pp.545-549.
Preto, S. and Gomes, C.C., (2018), July. Lighting in the Workplace: Recommended
Illuminance (lux) at Workplace Environs. In International Conference on Applied
Human Factors and Ergonomics (pp. 180-191). Springer, Cham.
Richman, E.E., (2015). Requirements for lighting levels. Pacific Northwest National
Laboratory: https://www. wbdg. org/pdfs/usace_lightinglevels. pdf, accessed April,
8.
Rodosthenous, G., (2016). Sound design in theatre: Interruptions, counterpoints and
punctuations− an interview with Mic Pool. Studies in Musical Theatre, 10(2),
pp.243-251.
Schoenwald, S., (2015). Flanking sound transmission through lightweight framed double-leaf
walls–Prediction using statistical energy analysis. Bouwstenen 127, ISBN 978,
pp.90-6814.
Schroeder, M.R., (2010). New method of measuring reverberation time. The Journal of the
Acoustical Society of America, 37(6), pp.1187-1188.
Sjöstrand, F.S., (2013). The ultrastructure of the outer segments of rods and cones of the eye
as revealed by the electron microscope. Journal of cellular and comparative
physiology, 42(1), pp.15-44.