Construction Technology 5 Report: Lighting Design Analysis

This report, prepared for a Construction Technology 5 course, delves into the crucial aspects of lighting design within the built environment. The report begins by differentiating between rod and cone photoreceptors, explaining their impact on visual perception and how these differences influence lighting design choices, especially in hazard and security applications. It then examines the effect of upward and downward light ratios, room design, and surface reflectance on light levels. The report further explores the influence of visual tasks, color appearance, and glare on lighting standards, along with the impact of atmospheric conditions, window design, and internal surface reflections on natural lighting. Finally, the report addresses the causes and mitigation strategies for glare, including reducing luminance, employing splayed windows, and increasing the angular displacement of illuminating devices. The document provides a comprehensive overview of lighting design considerations, supported by relevant references.

<University>
<Construction Technology 5>
by
<Your Name>
<Date>
<Lecturer’s Name and Course Number>
 <Your Name> 2018 1 of

Question 1
The rods are sensitive to low light levels (scotopic vision), slow to react to light
changes and are, sensitive to motion. The construction of the rods is simple, and
therefore images are registered quickly. Their persistence of vision is short which
makes them responsive to movement. These make the motion to be well monitored
out of the corner of the eye where there are more rods than where there are less or no
rods (Britannica, 2018).
Cone receptors are sensitive to high light levels (photopic vision), register colour,
distinguish fine detail and have a long persistence of vision. The cone photoreceptors
are only available on mammals and bird, but the colour perception is not perfect
(Pinel and Barnes, 2014). Cone receptors cannot register images quickly. Cones exist
in three types; blue, green and red and register light in different spectral ranges.
The above differences affect lighting designs in the following ways:
 For hazard lighting, the yellow and black marked barriers preferred for having
maximum contrast are made intense to ensure that the cone receptors can
operate.
 In places where detail perception is preferred; cones have to be responsible,
and in such cases, the brain has to adopt strategies to make sense of the visual
field.
 In the design of security light, sodium lamps are customarily a good choice
because they have yellow colour at night which is perceived to be at the centre
of the spectrum by the cones.
 <Your Name> 2018 2 of

Question 2
The relative proportions of upward light and downward light influences the light
levels in the work area (Abramovici and Stark, 2013). The luminaries that have a
portion of downward light increase the illumination on the task area as shown below:
Fig 1: Light Output Ratios
The lighting on the task is affected by the amount of light lost inside and by
transmission through the fitting, and the invisible light converted to heat. The more
elaborate the light fitting, the lighter lost as heat. Heat loss data analysis for different
light fittings is as below:
 <Your Name> 2018 3 of

The design of the room is the determinant factor of the amount of light that is
reflected back into space. Large cavernous areas are challenging to illuminate because
of the little light reflected bizarre surfaces (Portal, 2018). On the other hand, small
rooms have a lot of bounce lighting, and the amount of indirect illumination depends
on the room index obtained from the equation:
room index= Area of Horizontal planes
Area of Vertical planes
The area of the vertical surfaces is taken as the perimeter of the walls from the
mounting height of the luminaries to the height of the working plane. The horizontal
plane area adds to the luminaire plane and the working plane whose heights have a
negligible effect on the indirect illumination as explained in the diagram below.
 <Your Name> 2018 4 of

Fig 3: Room Index Calculations and Room proportions
The amount of light that falls on the work surface depends on the brightness of the
surrounding surfaces such a ceiling, walls, window and floor. Wood panelled rooms
always appear dark and dingy because there is a little indirect component of the task
lighting. Ceilings-boards are usually white to spread light.
Cleanliness of the luminaire and the room: light absorbed by dirty luminaires and
dirty surfaces depend on the rate of accumulation of dust. The type of the room, the
location of the place and the extent of cleaning for room surfaces and luminaries
affect the quality of lighting
The age whereby the reflectance of the area tends to decrease with age. The paintings
tend to fade diminishing the reflectance.
Question 3
The suitable lighting level depends on the visual task: the contrast, the fineness of the
detail and the speed at which the view varies (Portal, 2018). The following factors
determine the light standards for a workplace.
 <Your Name> 2018 5 of

 Colour appearance and colour rendering. As our eyes have over time
immemorial being developed to operate under natural lighting conditions their
sensitivity corresponds to the sunlight spectrum.
 The mood and the expected atmosphere help to decide on the colour
appearance. These are physiological and aesthetic effects. Light can be
handled purely functionally, but it is important to design it from the aesthetic
viewpoint (Abramovici and Stark, 2013).
 The function and psychological requirement of the visual task decide on the
directionality of the light.
 Glare can be done away with but to the acceptable extent that suit the
eyesight.
 A strong light signal is needed when fine detail is involved. Just a few
photoreceptors must be stimulated, while the surrounding receptors are
inactive. The expense of lighting increases in proportion to the amount of
illumination that you provide. Consider the table below indicating different
visual tasks and their range of luminance that is acceptable for the task.
 <Your Name> 2018 6 of

TASK LIMINANCE(lux)
Casual seeing 100
Ordinary tasks such as study library, general office work, show rooms and
laboratories
400
Severe, prolonged tasks; fine assembly and silk weaving 900
Exceptionally severe tasks such as watchmaking and watch repairs 2000
Assembling computer parts 5000
 <Your Name> 2018 7 of

Question 4
Atmospheric depletion.
The nature and the brightness of the sky affect the luminance of a given building.
During the day, the cloud can reflect light back out into space. Atmosphere and clouds
can absorb visible sunlight hence reducing the amount of natural light entering a
workplace in a given room (Science Daily, 2018).
The size, shape and the position of windows.
In side-lit rooms, the level natural daylighting rapidly decreases with the increase in
distance from the window. High windows usually allow daylight to strike the ceiling
plane and reflected into the interior. Monitors, skylights and clerestory windows help
to increase natural lighting entering a building. Consider the shown diagram:
The reflection from internal surfaces and obstructions from outside the room
classified into Internally Reflected Light (IRC) and Externally Reflected Light (ERC)
from the ground and other buildings. For the ERC, in arid and hot climates the glare
 <Your Name> 2018 8 of

experienced inside a building is produced from reflections from other buildings if
painted with light colours. The IRC component distributes light around the room.
Gleaming surfaces cause visual discomfort. This phenomenon is explained below:
The altitude and latitude at which the building is located
Sunlight which is the primary source of natural lighting has a less atmosphere to
travel through high altitudes. The very high altitudes are snow-bound, and this causes
a higher intensity of the sunlight due to ground reflection.
On the factor of latitude; at higher altitudes, the amount of natural lighting from the
sun is decreased by the angle of incidence as illustrated below;
 <Your Name> 2018 9 of

The position of the sun
The quantity of light into a building depends on the position of the sun. Daylighting is
minimum at sunrise and sunset because only half of the sun shines on the earth’s
surface. Maximum solar illumination occurs during the solar noon. The sun path
varies with the season, and latitude and this gives different orientations of natural
lighting to a building. For seasons (winter and summer) and latitude variations
consider the following diagrams:
Question5.
Excessive contrast causes typical glare. This is brought by:
1. Less luminous area (under-exposure).
2. Bright regions (over-exposure)
Under-exposure makes light to be scattered within the eye or in a luminous veil
leading to a condition known as disability glare. Background lights cause the subject
of concern to be overwhelmed.
On the other case, due to over-exposure to light, glare happens at high light levels
even at points of no contrast (Gago et al., 2015). Photoreceptors are unable to handle
 <Your Name> 2018 10 of

the high volumes of light intensity they are receiving leading to a condition known as
discomfort glare. An example of discomfort glare is white-outs observed at
snowfields.
Ways used to reduce glare in building are:
 Reduction of the luminance of the glare source achieved by window tinting, or
by screening the lights to minimise background brightness from windows and
lights respectively. Use of splayed windows diminishes daylight source
brightness into the building hence no glare. Use of overhangs, light shelves
and louvres help to reduce the intensity from direct sunlight, reduce contrast
from the sky and daylight into the building. Consider the figure shown below:
 By increasing the luminance of the surrounding area. To increase the light
levels, side lighting, side windows and use of light painted finishes can be
done in a building to reduce glare
 By increasing the angular displacement of the illuminating devices. The
window and the light placed at above 450 from the line of sight produces no
 <Your Name> 2018 11 of

glare. From the figure below, the light fitting does not cause glare on person
two because it is above the point of view.
 The shiny surfaces should be avoided to reduce glare. This is because they
cause the reflection condition. This condition depends on the angles of
incidence to the eye, and it is worst when the angle of incidence is at the same
line as the eye-line angle.
 Use of shielded fitting causes fewer glares as compared to a naked lamp
thereby reducing the size of the glare source.
 <Your Name> 2018 12 of