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TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
TEM Journal – Volume 7 / Number 4 / 2018. 829
Quality Assessment of the University Classroom
Lighting - A Case Study
Ivana Tureková 1, Danka Lukáčová
1, Gabriel Bánesz
1
1 Constantine the Philosopher University in Nitra, Faculty of Education, Department of Techniques and
Information Technologies, Dražovská 4, Post code: 949 74, Nitra, Slovakia
Abstract - The purpose of this study is to prove that
the quality of the school environment significantly
influences students’ academic performance. The
factors affecting the work environment are accurate
lighting which plays an important role in visual tasks,
resulting in either visual comfort or visual fatigue. This
study presents the results of lighting objectification of a
selected university classroom. Specifically, it focuses on
detection of the daylight factor, which is a significant
criterion for the amount of daylight in the classroom.
Its value is a relative magnitude and depends on the
correct spatial layout of the classroom. The results of
the study indicate the insufficient values of this
indicator. At the end, with a software, the solution for
replacing the artificial lighting in the classroom is
designed, which is a possible alternative for improving
the visual comfort of the classroom.
Keywords – daylighting assessment, visual comfort,
daylight illumination coefficient, DIALux.
1. Introduction
Daylight plays an essential and irreplaceable role
in human life. It affects one’s productivity, comfort,
mood and overall health. Its effects apply in mental,
as well as physical terms. The controlling body of
humans is directly stimulated and regulated by
daylight [1, 2]. Suitable illumination is vital in
DOI: 10.18421/TEM74-21 https://dx.doi.org/10.18421/TEM74-21
Corresponding author: Ivana Tureková, Constantine the Philosopher University in Nitra, Faculty of Education, Nitra, Slovakia Email: [email protected]
Received: 21 June 2018. Accepted: 10 October 2018. Published: 26 November 2018.
© 2018 Ivana Tureková, Danka Lukáčová, Gabriel Bánesz; published by UIKTEN. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License.
The article is published with Open Access at www.temjournal.com
children’s education, hence the strict regulations
governing the natural and artificial lighting in child
care and educational facilities. The majority of
children and students spend most of the day in
enclosed spaces where the sun penetrates in limited
quantities only. Most problematic is the winter time,
when the lack of light is most critical, although
a number of buildings struggle with proper amount of
daylight throughout the whole year. The main
struggle of educational buildings in Slovakia
nowadays is inappropriate thermal insulation,
inadequate microclimatic conditions in the
classrooms, absence of mechanical ventilation
systems or insufficient natural daylight [3]. Besides
lifestyle, genetic dispositions and healthcare quality
level, environmental conditions are amongst the
basic parameters that affect human health. The
impact of environmental factors (15 – 20 %) is the
second most important element influencing public
health [4]. This comes immediately after the
population lifestyle impact (50 %).
Daylighting is considered a resource of primary
importance in schools: it’s a key factor for
occupants’ health and well-being, enhancing the
indoor environmental quality and reducing the
energy consumption for electric lighting [5]. The
impact of natural light on learning has physiological,
psychological and behavioural influences on school
children as well as workers [6].
Humans are affected both physically and
psychologically by light [7]. As shown in Table 1.
there is a multitude of physiological and
psychological benefits resulting from building
daylighting [8].
Table 1. Natural light and human body
Natural light and human body
Physically Psychologically
Improve Decrease Improve Decrease
Vitamin D Cancer
Possibility
Mood Depression
Visual
System
Abnormal
Bone
Formation
Mental
Performance
Stress
Circadian
Rhythms
Alertness Sadness
Sleep
Quality
Brain
activity
Violent
Behavior
TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
830 TEM Journal – Volume 7 / Number 4 / 2018
There is no doubt that people find daylight more
pleasant than electric lighting as their primary source
of light. Foreign studies confirm [9, 10, 11, 12, 13,
14], that a high percentage of respondents surveyed
prefer working in daylight. Similarly, people prefer
to sit at tables located next to windows as opposed to
further in the room, especially when these windows
have access to direct sunlight [15, 16, 17, 18].
Thanks to light we are able to receive visual
information about the environment that we are
surrounded by 75 % to 90 % of these are received
through eyesight. The mental state in which the
visual system fulfils its function optimally is called
visual comfort. Suitable lighting is an essential
element here. Visual comfort is directly affected by
the lighting source, type and layout of the lights,
evenness, and level of luminance and brightness
distribution in space [14].
In terms of evaluation of work conditions, the
geometrical parameters of the space and surface
features, including colour, matter as well as whether
or not there is glare [19]. Lighting should be
sufficient and even, without excessive brightness or
contrast. If there is proper lighting distribution,
objects appear to be plastic. In suitable lighting
conditions one has a feeling of clear vision even after
a longer time. The opposite of visual comfort is
visual fatigue. This is a complex state due to
shortcomings in lighting. Symptoms include burning
eyes, headaches and conjunctivitis [20].
Even when it’s cloudy the lighting changes rapidly
over the course of the day. This is done to a greater
extent than we are able to realize as a result of the
adaptive ability of our vision (Figure 1.).
Figure 1. Changes in daylight illumination throughout a
cloudy day and the perception of these changes
The variability of daylight is an advantage to us, as
in a physiologically acceptable course it forces our
vision to adapt [21]. However, in terms of lighting
evaluation, the instability of daylight is a problem
most relevant in quality assessment (evenness,
brightness distribution throughout our vision field,
exclusion of silhouette effect or glare). Illumination
quality can be impaired at any state of sky, however,
mainly at direct sunlight. For instance, evenness
evaluation according to STN 73 0580-1/Z2 brings
inaccuracies because it is based on daylight factor
values set for evenly cloudy sky [22]. Therefore, at
this time there is no exact evaluation method, due to
instable daylight.
The daylight factor D (%) is determined by the
daylight rate coefficient in conditions of a cloudy
winter day according to formula [23]:
(1)
Where E (lx) represents illumination at the
observed location on a levelling plain and Eh (lx)
represents external illumination of the horizontal
unshaded plain (Figure 2.).
The daylight rate coefficient D (%) is a relative
value and therefore, unlike luminance E (lx), its
value is not so much subject to changes in the
brightness of the cloudy sky [19]. Relative simplicity
of the winter-cloudy model and its independency of
sun position or point of the compass enables us to
estimate D (%) by calculation and mathematical and
graphic methods [24] as well and by using a software
or measurements [25].
Figure 2. Illumination rates for a horizontal unshaded
plain with a cloudy sky in course of a day and a year
2. Method
The aim of our study was to determine the values
of illumination, the daylight illumination coefficient
and the expression of similarity or inaccuracy of the
results achieved with the limit values in the
representative classroom. Using the DIALux model a
new lighting system was designed [26].
For our experiment we selected a small university
classroom located in the building of the Faculty of
Education at Constantine the Philosopher University.
The room is situated on the ground floor and lectures
TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
TEM Journal – Volume 7 / Number 4 / 2018. 831
take place here frequently. It holds 24 students and 1
teacher. 15 meters far from the building there is
another building which could have an impact on the
daylight intensity in the measured classroom (Figure
3.). The foreside of the building where the classroom
is located is heat cladded and the whole building has
plastic windows.
Figure 3. A classroom where all measurements were done
- position of windows and the nearby building,
arrangement of furniture
The room orientation is north-west. Table 2. shows
description data of the space.
Table 2. Characteristics of sunlight and artificial lighting
system
Description of the office place
Walls Ceiling Floor
colour white colour white colour light
gray
material plaster material plaster material PVC
state of
surface
clean state of
surface
clean state of
surface
clean
Description of lighting system
Natural lighting
system:
2 windows 800 x 1100 mm
Artificial lighting
system:
4 pieces of lamps
number of light
sources in lamps: 4
pieces
Type of light
sources:
TESLA, PHILIPS
TL-D
Power input: 36 W
Position of light
sources:
regular, symmetric
Located 15 meters from the researched classroom,
there is another building which significantly affects
the daylight intensity in the school.
Particular measurement was performed by a light
meter Testo 545 (Figure 4.). It was extremely
accurate measurement since the permissible
deviation defined by producer was ±2% (according
to DIN 5032, part 6).
Figure 4. Apparatus Testo 545 that was used for lighting
measurement
The lighting measurements were executed in
March 8.00 - 15.00 hour. This included 8
measurements of sunlight, 8 measurements of
compound lighting and 3 measurements of artificial
lighting.
The aim of objectification was to detect the current
state of a workplace. Illumination was measured
within the net of 20 selected control points [27].
Height of the datum plane was 0.85 m above the
floor, distances between measuring points were 1 m
and the outer points of the net were less than 1.5 m
from the wall.
Other control points were distributed in regular
distances so that they can adequately monitor the
whole measured place, changes in lighting and also
places with the highest and lowest intensity of
lighting. External conditions were measured by
anemometer (psychrometer) AN 340.
3. Results
Table 3. shows the results of external conditions in
which the measurements took place.
Table 3. External conditions in measurements
Temperature
(°C)
Humidity
(%)
Wet
thermometer
temperature
(°C)
Condensation
point
(°C)
23.6 32.8 13.9 6.2
Average daylight values are presented in Figure 5.
At 11 o’clock the daylight amounted to a maximum
value measured (507,4 lx). In the morning and in the
afternoon the values were considerably lower (100 –
200 lx).
TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
832 TEM Journal – Volume 7 / Number 4 / 2018
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00 1563.63
1189.38
958.25 831.38
1413.13
1147.88
978.25 882.38
1214.25 1172.75
1044.13 905.63
1488.63
1277.63 1184.38
933.63
1557.38
1243.50
1046.50
781.50
Figure 5. Average daylight values in the classroom from 8 am to 3 pm
Table 4. presents daylight values, measurement
uncertainty and illumination requirements by STN
EN 12464-1 : Light and Illumination.
Table 4. Measurement results and Illumination
Requirements.
Ē
(lx)
U
(%)
Ē – U
(lx)
Ē + U
(lx)
Illumination
requirements by
STN EN 12464-1
426.13 34.09 392.04 460.22 500 lx
At the same time, measurement of combined light
was carried out by turning on every light source in
the classroom in the same measuring points. We have
determined the average illumination of the classroom
(Ē) based on the arithmetic mean of the measured
values of the overall scaled horizontal illumination in
the whole of the measured space or combined
illumination on the comparison plain (Figure 6.).
The lowest values were on average about 1000 lx,
which meets the illumination requirements
(minimum of 500 lx) for educational spaces [28].
Figure 6. Average combined illumination values in the course of a day in the classroom.
0.00
200.00
400.00
600.00
800.00
1000.00785.25
443.13
243.13 176.875
790.38
438.50
290.88 193.63
559.57
439.71
302.29 210.63
835.25
466.63
297.63 187.38
902.63
476.25
312.25
170.63
TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
TEM Journal – Volume 7 / Number 4 / 2018. 833
Table 5. presents the values of combined
illumination, measurement uncertainty and
illumination requirements by STN [28].
Table 5. Combined Illumination Values.
Ē
(lx)
U
(%)
Ē – U
(lx)
Ē + U
(lx)
Illumination
requirements by
STN EN 12464-1
1140.71 91.26 1049.45 1231.97 500 lx
Table 6. summarizes the values of 20 measuring
points of average daylight values, external
illumination at cloudy sky in winter (there was a set
of 20 measuring points constructed, similar to the
one in the classroom) and artificial lighting in the
classroom by using only the existing lighting sources.
The last column contains the daylight illumination
coefficient D (%) calculated by using the formula
(1).
Table 6. Results of measuring daylight and artificial light, calculation of daylight illumination coefficient
Measuring
point
Average
daylight values
(classroom)
Ē (lx)
Average values of
combined lighting
Ē (lx)
Artificial
lighting values
Ēartificial (lx)
Average
daylight values
outside
Ēoutside (lx)
Daylight
illumination
coefficient
D (%)
1. 785.25 1563.63 840.15 12520 6.3
2. 443.13 1189.38 820.35 14310 3.1
3. 243.13 958.25 894.71 14170 1.7
4. 176.88 831.38 829.53 13880 1.3
5. 790.38 1413.13 1003.23 14210 5.6
6. 428.50 1147.88 1033.44 13250 3.2
7. 290.88 978.25 1057.53 13780 2.1
8. 193.63 882.38 999.92 14010 1.4
9. 559.57 1214.25 825.74 13360 4.2
10. 438.71 1172.75 894.58 13450 3.3
11. 302.29 1044.13 943.16 13780 2.2
12. 210.63 905.63 873.06 13970 1.5
13. 835.25 1488.63 751.22 12890 6.4
14. 466.63 1277.63 720.81 13580 3.4
15. 297.63 1184.38 852.14 13560 2.2
16. 187.38 933.63 753.26 12790 1.4
17. 902.63 1557.38 790.78 14120 6.4
18. 476.25 1243.50 767.83 13480 3.5
19. 312.25 1046.50 786.21 12780 2.4
20. 170.63 781.50 730.34 13010 1.3
Average
value 425.58 1040.71 858.40 13354 3.2
Table 7. present artificial daylight values,
measuring uncertainty, and illumination requirements
by STN EN 12464-1: Light and Illumination.
Daylight illumination coefficient D (%) as one of
the criteria of daylight amount has to meet the
following requirements:
Inside the premises or in their functionally
specialized parts where employees spend a lot of
time the minimum values of the daylight illumination
coefficient must be:
a) At side illumination Dmin = 1,5 %
b) At top and combined illumination Dmin = 1, 5
% and Dm = 3 %, where: Dmin is the minimum
value of the daylight illumination coefficient
on the comparison plain (%);Dm – the average
value of the daylight illumination coefficient
on the comparison plain (%).
Table 7. Artificial daylight values and illumination
requirements
Ē
(lx)
U
(%)
Ē – U
(lx)
Ē + U
(lx)
Illumination
requirements by
STN EN 12464-1
857.95 68.64 789.31 926.59 500 lx
The values of average illumination we obtained by
the measurements and calculations were rectified by
measurement uncertainties set against the
illumination requirements. Technical solutions for
improving lighting systems are relevant while project
processing and reconstruction. Various modelling
programmes offer a range of lighting system
solutions. Through DIAlux programme a new
lighting system was drafted using LED lights, while,
preserving the arrangement of the existing lighting
system (Figures 7., 8.).
TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
834 TEM Journal – Volume 7 / Number 4 / 2018
The lights were selected from the options in the
programme - 12 pcs of PHILIPS CR200B 2xTL5-
54W HFP GT_452 (luminous flux 5852 lm; Lamp
power: 118.0 W).
Figure 7. Modelling room arrangement.
Figure 8. 3D model of the classroom and the proposed
lighting.
Figure 9. Rendering of place by false colours
4. Discussion
The results obtained can be summarized within the
the following conclusions:
a) The lighting in the selected classroom cannot be
sufficiently illuminated by daylight alone as
daylight cannot provide the required lighting
intensity.
b) Combined lighting values as well as artificial
lighting values meet the required minimum.
Hence, with lighting units turned on, the required
limit values are met.
c) The obtained values of artificial lighting are
sufficient, as none of the values dropped below
500 lx.
d) The amount of daylight measured by the daylight
illumination coefficient appears to be sufficient
because 3 of the values have fallen below 1, 5.
This means that the space is not provided with
sufficient light for mental and physiological
influences as well as for contact with the outside
environment. If, for some reason, lighting is
higher than daylight, the lighting of daylight
must be supported by artificial lighting, which is
not considered as combined lighting.
e) Optimal working temperature in the room met
the required parameters for temperature –
humidity microclimate for cooler seasons (from
18 °C to 26 °C).
f) Required relative air humidity in the classroom
in cooler seasons should amount to 30 % -70 %.
Our values are between 30,3 % to 35,9 % which
means the humidity requirements have been met
as well.
TEM Journal. Volume 7, Issue 4, Pages 829-836, ISSN 2217-8309, DOI: 10.18421/TEM74-21, November 2018.
TEM Journal – Volume 7 / Number 4 / 2018. 835
It is necessary to mind the ceiling lighting sources
besides external daylight, considering that the values
of daylight alone without using the support of any
artificial light did not meet the required lighting
intensity and required value of daylight illumination
coefficient. Especially in winter months, daylight
alone is not sufficient and needs to be supported by
artificial lighting sources in order to prevent visual
fatigue and other health issues.
The natural light penetration into the classroom
must be ensured by regularly cleaning the covers of
the lighting systems and window openings,
maintaining clean wall surface, ceiling and floor.
Designers, teachers and all people who are
involved with educational environments must
consider the lighting and controlling it. Physical area
in designing is very important and lighting is one of
the most important features in physical area in all
environments especially in educational and working
environments [29]. Despite the fact that good lighting
makes workspace more efficient, the lighting system
is always regulated by the human factor. Modern
technologies already offer lighting based on natural
daylight. For example, the light is automatically
adjusted by the control system. The sensor inside
measures the daylight amount and maintains the
lighting level for a given time, depending on daylight
availability which guarantees energy savings.
Different scenarios (with varying degrees of
chromaticity and light intensity ratios) are presented
in the control system [1].
5. Conclusions
Good lighting is a key to creating successful living,
working and learning environment, and is necessary
to ensure safety, as well as, well-being, health and
quality of life. By objectivizing the lighting, we
pointed out the deficiencies in the internal
environment of the university classroom. A major
shortcoming in the design of the classroom is due to
another building being immediately adjacent to the
researched building. This causes shadowing and
insufficient daylight flow into the room even though
the daylight coefficient met the required values. At
the moment, only alternative solutions can be taken,
which can bring not only light comfort but also
energy savings. However, other parameters such as
humidity, air flow, temperature, noise or chemical
factors are very closely related to the building's
suitability. Therefore, improving the lighting is
important, however, at the same time, maintaining
the classroom with both appropriate air conditioning
and regeneration systems is necessary, so that the
inner environment well-being, impacts the
performance of the student and the teacher positively,
and does not result in discontent.
Acknowledgements
This article was supported by the Grant Agency
Ministry of Education SR KEGA - project no.
014UKF-4/2016.
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