UWS Architecture: Light, Rods, Cones, and Lighting Design in Buildings

This assignment delves into the science of light and its impact on human vision and architectural design. It begins by explaining the differences between rods and cones in the human eye, detailing how these photoreceptors affect our vision in various lighting conditions and subsequently influencing lighting design for different tasks. The assignment then identifies and elaborates on five critical factors that influence required light levels in a workplace, including workplace size, task types, occupant age, building materials, and location, supported by diagrams. Furthermore, it discusses how to determine appropriate light levels for specific work surfaces, providing examples of visual tasks and acceptable illuminance ranges. The impact of natural light is examined, listing five key factors affecting the amount of natural light in a building, such as floor layout, obstructions, building form, shading, and orientation, again with illustrative diagrams. Finally, the assignment defines and differentiates between two types of glare—disability and discomfort—explaining their causes and offering measures to reduce glare in buildings, accompanied by diagrams to illustrate these techniques. This comprehensive exploration provides a thorough understanding of lighting principles and their practical application in architectural and workplace design. Desklib provides a platform to explore more solved assignments and past papers.

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ASSIGNMENT 1: LIGHT
By (Name)
Course
Professor’s name
University name
City, State
Date of submission

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Q1. Describe how the differences between the rods and cones in the human eye affect our
vision. Explain how these differences affect lighting design for different tasks. (20 marks)
Rods and cones are photoreceptor cells. They are both located in the retina. Rods are
located on the outer layer of the retina and function well at night or when there is less light. The
rods help the human eye to see in low levels of light but it is limited to identification of different
colors due to its achromatic nature which is simply the inability to differentiate different colors.
Rods also have low acuity and therefore affects the sharpness with which the eye can form
images in low light. The low response nature of the rod is another characteristic of that affects
how quick one’s eye can be able to adjust when in dim light (Dubra et al., 2011). Cones on the
other hand are found at the center of the retina and are the cells that enable the eye to form
images in light (Dubra et al., 2011). Cones are quick to respond to changes in light, they have
high acuity levels and thus in apposition to form sharp and acute objects. Its chromatic nature
allows the eye to differentiate different colors.
When developing different sources of light, it is quite important to factor is the different
attributes of the two photoreceptors in the eye. For instance, when designing lighting of office
spaces, it could be of different colors due to the ability of the cones to differentiate color. In
darkness the designs of the source of light should be of a single color due to the inability of the
rod to identify different colors.

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Q2. Acceptable light levels are dependent on the nature of the task being undertaken. List
five distinct considerations that may influence the required light level in a workplace
situation. Explain these factors with diagrams. (20 marks)
1. The size of the work place.
Larger work spaces would require high levels of light to enable the whole building to be
lit (Cuttle 2010). This may entail using different sources of light or a single source that is
powerful enough to light the whole premise. An example is an open plan office with a
capacity of up to fifty employees.
2. Task undertaken at the work place.
Different duties and roles will require varying amounts of light to be executed. For
example, in an office set-up where the light is required for filling and reading through
documents that the levels should good enough. In the case of a warehouse, the levels of
light may not be that high but should be enough to guarantee safety and movement of
products (Dianat et al., 2013).
3. Age of occupants
In an establishment with young employees, the light levels should not necessarily be that
high but in a case where majority are old then high levels of light should be considered.
With age comes a reduction in the sense of sight.
4. Fabric and design of the work place.
Different materials react differently to light. For example, mirrors will reflect light and
thus spread it to other parts of the room whereas opaque material absorb light. Therefore,
is a workplace with more transparent and reflecting materials require less levels of light
and the opaque need more light.

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5. Location of the work place.
An outdoor kind of workplace will require minimal light from artificial sources whereas
the indoor will be in need of higher levels of light depending on the number and designs
of windows used.
Q3. Explain how you would decide what light levels are required on a work surface for
particular workplaces. Give at least five examples of different visual tasks and state the
range of illuminance that is acceptable for that task. (20 marks)
Task lighting located in the interior spaces of a building always have a specific task. In most
cases, it is aimed in brightening up a particular area that requires more light than ambient
lighting. It can be provided in recessed wall lighting, track lighting (Cantin and Dubois 2011),
under cabinet lighting and pendant lighting, including the desk lamps that are portable. Task

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lighting are free from any form of shadow and distraction that may cause glare and should be
bright to provide clear vision without causing any strain. There are certain factors that determine
the use of task lighting in a space. This parameters include;
 When the task to be carried out cannot be lit by general lighting due to path obstructions.
 Visibility depends on illuminating the texture by shadow.
 The modest level of illumination in the background is supported by special lighting in the
spaces where the task is being done.
The main consideration of lighting design is the illuminance levels required in a certain area or
the mount of light reaching that particular surface. The amount of light specified is usually
referred to as illuminance measured in Lux. This level varies depending on the task within a
specific space. Area that require keen concentration on a particular task will require more visual
light such as reading table, classroom, offices etc. while spaces that require service illuminance
such as the kitchen, toilet will have reduced levels of illuminance (Smolders, De Kort, and
Cluitmans 2011). Generally, illuminance required in a specific task depends on the visual
difficult of the task being carried out, the type of performance expected and the average standard
of eye sight involved. However, illuminance is affected by the angle and distance between the
source and the illuminating surface and the reflectance of the surrounding surface.
Lux Level Work Activity User Area

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100 – 140 Casual non-visual task Corridors, offices, changing rooms
150 – 180 Some perception of detail Warehouses, stores, lift lobbies
200 – 240 Continuous occupation Dining rooms, entrance halls
250 – 300 Very easy visual task Classrooms, Public toilet
300 – 400 Moderately easy visual task Libraries, Private office, lecture
theatres
500 – 600 Moderately difficult visual task Offices, retail outlets, laboratories
750 – 900 Difficult visual task Supermarkets, technical drawing
offices
1000 – 1300 Very difficult visual task Polishing, painting plant, Operating
theatres
Source: https://www.ccohs.ca/oshanswers/ergonomics/lighting_survey.html

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Q4. List at least five important factors that affect the amount of natural light falling on a
work surface inside a building. Using diagrams explain how this works. (20 marks)
The sun is always the source of natural light and heat that is both unwanted and desirable. The
amount of natural light falling on a surface inside a building can be affected by a number of
factors which include;
 The depth of the floor layout
 Obstruction from sky illuminance
 The form and volume of the building
Figure 1: Notre Dame du Haut design by Le Corbusier, Ronchamp (1950) fenestration shapes
affect how light is illuminated into the space
Source: http://thedaylightsite.com/light-and-materials/
 Shading effect on the windows or spacing of blocks

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Figure 2: Lights shelf spread the light evenly into the room
Source: https://www.education.govt.nz/assets/Documents/Primary-Secondary/Property/School-
property-design/Flexible-learning-spaces/BranzLightingDesignGuide.pdf
 The orientation of the building with respect to the source of the light.
Figure 3: https://greenpassivesolar.com/passive-solar/building-characteristics/orientation-
south-facing-windows/
There are two important consideration to take in large glazed areas; ensure there is balance
between daylighting with glare or overheating (Lechner 2014). This is one of the main
challenges faced in the tropical regions to achieve a sustainable design. To achieve the required
level of illuminance on our task surfaces, the visual tasks can be moved close to the window or
complimented with artificial light.

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Q5. Name and describe the two different causes of glare which may cause disability or
discomfort depending on the magnitude of the effect. With diagrams describe what
measures can be used to reduce glare in buildings? (20 marks)
Glare is the impairment of vision or the discomfort caused by excess light brightness in the
visual field. It can be caused by painted surfaces, windows, and lamps brightness in relation to
the adjacent surface. Such type of glare is called contrast glare.
Disability glare reduces the ability of the cone to see details, may be caused as a result of visual
discomfort caused by excessive reflections that comes from a white paper or book when reading
it.
Discomfort glare causes a certain degree of visual discomfort without the effect of reducing the
ability to see details. For example the light bulb that is unshielded. The level of discomfort is
mainly influenced by the type of location and angle of view. When light is fixed on a visual task,
the light may be so pronounced to cause glare. Discomfort glare mostly happens when the
illuminance ratio is;
Lmax / Lmin > 15

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Glare can also be caused directly or indirectly as a result of the reflected light from the
illuminated surface. Reflected glare can also occur when the reflected glare is caused by a lamp
positioned behind a laptop or computer or bright light from the sun passes through the window
behind a computer operator then falls on to the screen causing the glare.
Figure 4: Reflection of a window on a screen
Source: https://www.education.govt.nz/assets/Documents/Primary-Secondary/Property/School-
property-design/Flexible-learning-spaces/BranzLightingDesignGuide.pdf
Methods of reducing glare in a building
 Reducing the field of illuminance by using a glass with low transmittance, where t =0.3,
especially for upper window parts. This can be achieved by use of blinds or solar film,
tinting and curtain.

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Figure 5: Tree obstruction, curtain walls and light shelf
Source: https://www.wbdg.org/resources/sun-control-and-shading-devices
 Areas near high luminance view should have an increased level of luminance. This can
be achieved by having windows in opposite walls to light surfaces adjacent to the
window.
Figure 6: Light colored surfaces improve lighting efficiency
Source: https://www.education.govt.nz/assets/Documents/Primary-Secondary/Property/School-
property-design/Flexible-learning-spaces/BranzLightingDesignGuide.pdf
 Increase luminance of walls areas around the window by using light colors on walls and
contrast grading.

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 Blocking out the view of brightness using shading devices that are brightly colored to
reflect excess light that may cause glare.
Figure 7: Shading performance, redirection devices Illustration by RNL Design