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THE FIRST TEST OF INDOOR AIR QUALITY IN KINDERGARTENS OF THE REPUBLIC
OF SRPSKA
Biljana ANTUNOVIĆ1*, Aleksandar JANKOVIĆ2, Darija GAJIĆ1, Nevenka ANTOVIĆ3, Jelena
RAŠOVIĆ1, Zoran ĆURGUZ4, Milan POPOVIĆ5
1 University of Banja Luka, Faculty of Architecture, Civil Engineering and Geodesy
2Norwegian University of Science and Technology, Faculty of Architecture and Design
3University of Montenegro, Faculty of Natural Sciences and Mathematics
4University of East Sarajevo, Faculty of Transportation
5University of Banja Luka, Faculty of Natural Sciences and Mathematics
*Corresponding author; E-mail: biljana.antunovic@aggf.unibl.org
The first experimental results of the indoor air quality in two kindergartens
located in the Republic of Srpska are presented in this paper. Kindergarten
representatives for the year of construction (old and new), building
materials, and energy efficiency have been chosen. Indoor air quality
measurements (air temperature, relative humidity, ventilation rate, CO2,
and radon concentration) were performed during the winter of 2015/2016.
Measured indoor air quality parameters are discussed and compared to the
international standards BAS EN 16798-1, ASHRAE 62.1, and ISO 7730. The
average measured radon concentrations for both buildings have not
exceeded the level of 200 Bqm-3, but for reliable results, long-term
measurement needs to be performed. The CO2 concentration in the old
kindergarten fulfills the BAS EN 16798-1 requirement for category I during
62.43% of total occupancy time, while for the new kindergarten, it is only
5.79% of full occupancy time. Results of CO2 concentration confirm that
good sealing of the envelope of new buildings and user behavior (number of
users and natural ventilation) does affect air quality. Furthermore, a high
correlation between CO2 concentration and relative humidity in both
buildings and a more considerable correlation for the new building have
been observed.
Keywords: indoor air quality, kindergarten, temperature, relative humidity,
number of air changes, CO2 concentration, radon concentration
1. Introduction
Indoor Environmental Quality (IEQ) is a comprehensive term that includes various
factors: indoor air quality (IAQ), lighting, thermal comfort, acoustics, drinking water, ergonomics,
electromagnetic radiation, and many other factors [1].
Per the EPA definitions, Indoor Air Quality (IAQ) refers to the air quality within and around
buildings and structures, especially as it relates to the health and comfort of building occupants [2] To
evaluate IAQ, pollutant concentrations, thermal conditions (temperature, airflow, relative humidity),
light, and noise are generally analyzed [3]. Indoor air pollution has been determined by the
concentrations of pollutants present in the air (formaldehyde, volatile organic compounds, particles,
pesticides, radon, fungi, bacteria, and nitrogen oxides), while its elevated concentrations can cause
Lung cancer Legionnaires' disease, carbon monoxide poisoning, allergy, and asthma [4]. According to
some papers, thermal comfort represents the most crucial aspect of IAQ [3]. The concept of indoor air
quality in science became significant during the global energy crisis in the 70s when there was an
increase in energy prices. Consequently, there was a need for economical consumption of thermal
energy to protect the environment and reduce CO2 emissions [5]. The essential action required was to
decrease the heat losses in buildings by addressing both transmission and ventilation to lower energy
consumption for heating buildings. Reduction of ventilation losses due to infiltration is achieved by
better sealing of the envelope, which, on the other hand, causes more significant indoor air pollution.
Indoor air quality and pollution of the air are essential aspects of the comfort and health of inhabitants
in all building types. Still, they are vital for kindergartens, where children spend most of their time
during the day in the most sensitive period of their growth and development. The kindergarten opening
hours are 7 a.m. to 5 p.m. from Monday to Friday. On average, that time is 8 hours per day and five
days per week, which is around 50 weeks or 2000 hours on a year level. In addition, children spend at
least the same amount of time in a closed space at home. Indoor air quality and pollutants that could be
present in the air can cause discomfort, affect the learning performance of children, and, last but not
least, cause long and short-term health problems [6, 7]. Furthermore, children are more sensitive to air
pollutants and at higher risk for developing diseases and cancer than adults [8, 9]. A precondition for
good indoor air quality is adequate fresh air supply (ventilation), quantified by the required air changes
per hour. It depends on the quality of the outdoor air. Also, the indoor concentration of CO2 can give
insights into the air quality in the room, but it depends on occupancy and ventilation rate. According to
papers [10, 11], a high correlation between CO2 concentration, relative humidity, and indoor air
temperature in naturally ventilated buildings is expected. The International Standard BAS EN 16798-1
[6] introduces different categories of building materials depending on the pollution. The building is
"very low polluting" if all of the materials are very low polluting and if smoking is prohibited and not
practiced. The standard defines "very low polluting materials" as traditional natural materials, such as
stone, glass, and metals, which are known to be safe with respect to emissions, etc.
As important aspects of indoor air quality in kindergartens, the radon concentration, the
concentration of CO2, the internal air temperature and relative humidity, and air changes per hour are
measured and analyzed in this paper.
2. Methodological Approach
To evaluate the air quality in the kindergarten's indoor space, measurement methodology has
been introduced (Fig. 1). In the theoretical part, the definition of the radon concentration, CO2
parameters, and their prescribed values are discussed. Furthermore, the case studies of kindergartens
taken from different construction periods, showing typical representatives of old and new kindergarten
construction and their characteristics, are considered. The representative of the old construction is a
kindergarten built 40 years ago, as are most existing kindergartens that need to be renovated. On the
contrary, the exemplar of modern construction is the kindergarten, constructed according to the
parameters prescribed in the currently valid rulebook, as a low-energy building. Moreover, the
measuring instruments, their characteristics, and the standards used to perform measurements are
introduced. The characteristics of the rooms where the measuring devices were installed are also taken
into consideration. The experimental part of the research was carried out in selected kindergartens.
The air quality parameters in typical, characteristic rooms for children were carried out in the
experimental part of the research (Fig. 1).
Figure 1. Scheme of the methodological approach
The results of the measurements are discussed in a comparative analysis of two kindergartens.
The radon in the indoor space and the CO₂ concentration, temperature and air humidity in the indoor
and outdoor spaces, and the number of air changes per hour are measured and analyzed in order to
have an adequate discussion about the quality parameters of the indoor environment. Finally, the
correlation coefficients between CO2 and temperature and CO2 and relative humidity are presented and
discussed.
3. Theoretical part: Definition and prescribed values of parameters
The theoretical basis for parameters used to evaluate internal air quality (the radon
concentration, the CO2 concentration, and the number of air changes per hour) is introduced in this
chapter.
3.1. The radon concentration
According to the UNSCEAR 2000 report, the annual global average effective dose from natural
radiation (cosmic radiation, external terrestrial radiation, inhalation, ingestion) is 2.4 mSv (public
exposure). Almost half of this total received dose comes from radon inhalation [12].
Radon (222Rn) is the most widespread natural radioactive gas, tasteless, colorless, odorless, and
inert. Generally, the ground under (and around) the building is the primary source of radon in indoor
air [13]. Building material is the second leading source of radon in indoor air, particularly on the upper
floors [14, 15]. The results from the previous papers confirmed that usually, the most significant
influence on the total radon concentration up to the second floor in an enclosed space is radon from the
soil. Radon emanating from the material used during construction, i.e., built into the walls or floors, is
more significant for the upper floors. The other sources of radon indoors are gas, water supplies, and
outdoor air. It should be noted that the global average indoor radon concentration is found to be 46
Bqm-3 with a geometric mean of 37 Bqm-3, while its typical outdoor concentration is of the order of 10
Bqm-3 [12, 16].
Special attention must be paid to the energy-efficient buildings which, due to energy saving for
heating and cooling, strive to lower air exchange with the outdoors (airtightness). Increased
concentrations of this gas are dangerous to health. The danger of radon to human health arises from
inhaling short-lived decay products (polonium isotopes) that can deposit in lung tissue and damage it
by emitting alpha particles. According to the results of studies, radon and its short-lived daughters are
considered the second leading cause of lung cancers after smoking. Furthermore, it is essential to
emphasize that children are more susceptible to radiation exposure than adults from slightly enhanced
natural radiation [8, 9].
Regulations concerning the population's exposure to radon and its descendants differ in different
countries. However, new recommendations have been introduced recently in light of new scientific
data. The EU Directive 2013 requires establishing a national reference level for indoor radon annual
average activity concentration not exceeding 300 Bqm-3 – for residential dwellings and workplaces
[17]. To minimize health risks due to radon exposure, the WHO recommends a reference level of 100
Bqm-3, and certainly not higher than 300 Bqm-3 [18].
3.2. The CO2 concentration
Carbon dioxide (CO2) is a colorless and odor-gas component of atmospheric air. The amount of
CO2 in the outdoor air is variable (around 0.04 %). It is one of the indoor pollutants emitted by
humans, furniture, buildings, and HVAC systems, affecting humans to experience drowsiness, develop
headaches, and so on. Since kindergartens are buildings with special requirements as susceptible
persons use them as young children, they have classified the building category I according to the
standard BAS EN 16798-1 [6]. Some recent studies indicate that the indoor concentration of CO2 is
strongly influenced by the number of occupants in the rooms and their times of stay. CO2 measured
values might indicate problems with ventilation adequacy, but the CO2 concentration does not indicate
air pollutants that are not perceivable by humans, such as radon. According to international standards
(including The American Society of Heating, Refrigerating and Air-Conditioning Engineers –
ASHRAE [19]), acceptable indoor levels of CO2 should not exceed 1000 ppm. At the same time, the
difference between the indoor and the outdoor concentration should satisfy specific criteria depending
on the building category. The CO2 concentration, as a parameter of IAQ, is directly affected by the
ventilation rate.
The air change rate is characterized by the number of air changes per hour, representing the
ratio of the exchanged air volume in one hour and the total net volume of the room n [h-1]. The number
of air changes per hour is one of the parameters that directly shows the indoor air quality. From the
design point of view, a specific air change rate is required depending on the building envelope's
thermal characteristics, the building's position to the surroundings, the microclimate conditions, and
the use of the building. Also, health and comfort criteria directly influence required ventilation and the
number of air changes per hour. According to the national regulations in the Republic of Srpska [20],
the measured number of air changes per hour, when the difference in pressure between the indoor and
the outdoor air is 50 Pa, has to be three h-1 for naturally ventilated buildings.
The measured indoor and outdoor values of air temperature, air humidity, and the concentration
of CO2 are presented separately, as well as through the correlation coefficients between CO2 and
temperature and CO2 and relative humidity.
4. Case study part: Typical kindergartens and measuring instruments
Two kindergartens (Neven and Kolibri) in Banja Luka in the Republic of Srpska have been
chosen for the presented case studies.
4.1. Characteristics of analyzed buildings
Kindergarten Neven, with design documentation dating back to 1974, represents an example of
an old building, while kindergarten Kolibri, with design documentation dating back to 2008, has been
taken as an example of a new and modern built kindergarten according to energy efficiency rulebooks
of the Republic of Srpska [20, 21, 22]. The two buildings are similar in terms of site, size, and design
number of users (Fig. 2). They both accommodate ca. 220 children aged 1-6, divided into eight
groups.
Both kindergartens are located in an urban area, surrounded by other buildings, and have similar
ventilation conditions since they are both naturally ventilated. Neven has a central heating system with
radiators installed on the external walls. In contrast, Kolibri has a floor heating system (low-
temperature regime) heated through a water-water heat pump with an underground thermal spring.
Furthermore, Neven has no compact form, and its building shape factor is 0.94. On the other hand,
Kolibri has a widespread ground floor size with a larger part that includes a gallery, which increases
Figure 2. The view of the kindergarten from the yard and layout of the ground floor:
Neven (left) and Kolibri (right)
kindergarten volume with a building shape factor of 0.77. The old kindergarten, Neven, is a
prefabricated reinforced concrete frame structure with brick infill walls. The new kindergarten is a
masonry structure with load-bearing brick walls and reinforced concrete ring beams. The average U-
value of the elements of the envelope is presented in Tab. 1 and for two buildings, they are different
due to the different designs and materialization of the envelopes, resulting in Kolibri satisfying the
criteria of energy-efficient buildings.
Table 1. Characteristics of the Kindergartens
Neven (old)
Kolibri (new)
No of floors
P
P+G
Heated space area [m²
1014
1110
Heated space volume [m3
3044
4157
U-value walls [Wm-2K-1]
1.47
0.41
U-value windows Wm-2K-1]
3.55
1.51
U-value roof Wm-2K-1]
0.77
0.20
U-value floor Wm-2K-1]
1.12
0.33
g-value
0.77
0.61
A/V ratio m-1]
0.94
0.77
Number of users
217 children, 18
nurses/nursery/preschool teachers
224 children, 16
nurses/nursery/preschool teachers
Number of users per room
28
25
4.2. Characteristics and setting of measuring instruments
Tab. 2 lists measured IAQ parameters, the names of devices used for measurement, and the
corresponding standards.
Table 2. Characteristics of the equipment
Parameter
Equipment
Standard
The airtightness
Minneapolis Blower Door,
Model 4 220V SYSTEM
ISO 9972
ISO 13789
The radon concentration in indoor air
RAD7 DURRIDGE Radon
Detector
active method
The CO2 concentration, air temperature,
and relative humidity
TESTO 435-2 with the
adequate IAQ probes
BAS EN 16798-1
Thermal irregularities
Testo 885-2
EN 13187
The electronic detector of alpha particles, the RAD7 DURRIDGE Radon Detector (Fig.3), has
been used to measure the radon concentration in indoor air. The detector produces a signal with a 50%
probability. This signal is amplified electronically and transformed into a digital signal. The
microprocessor stores the energy level of the signal and produces the spectrum. The manufacturer
recommends that the device works at standard room temperature and air humidity up to 6% when the
device error is 4%. All deviations from these values are corrected by the program which controls the
detector RAD7.
According to the standard BAS EN 16798-1 [6], air quality can be determined by measuring the
CO2 concentration in a fully occupied building. The measurement was performed using TESTO 435-2
with adequate IAQ probes for CO2 concentration, relative humidity, indoor air temperature, and
absolute pressure (Fig. 3). The data logger records CO2 concentration in the range 0-10000 ppm, with
accuracy ± (0-5000 ppm CO2: 75 ppm CO2+3% mv). The measurement range for air temperature is
20-70 C and relative humidity 0-100% RH with the accuracy ±0.5 °C and ±3% RH, respectively.
The standard defines different acceptable levels for each building category depending on the
indoor CO2 concentrations above the outdoor level. Since users of kindergartens are children in their
most sensitive period of growth and development, these types of buildings can be defined as buildings
of category I due to the high level of expectation according to BAS EN 16798-1.
Both kindergartens are ventilated naturally. The airtightness of analyzed buildings is tested with
the Minneapolis Blower Door (Fig. 3) measuring equipment according to the methodology defined in
the standard ISO 13789 [23]. Due to kindergartens' large net heated space volume, only representative
rooms are tested following ISO 9972 [24].
During measurements, qualitative detection of thermal irregularities on the envelope was carried
out using an infrared method with Testo 885-2 (Fig. 3) following EN 13187 [25].
Figure 3. Devices used for measurement: RAD 7 (left), Testo 435-2 (middle-left), Minneapolis
Blower Door (middle right), Testo 885-2 (right)
5. Experimental part: The results of the measured parameters in kindergartens
The measurements of indoor air quality parameters were performed on the ground floor of
kindergartens Neven and Kolibri during December 2015 and February 2016, respectively. The
analysis of the obtained measurements of the radon and CO2 concentration, air temperature and
relative humidity, and number of air changes in the representative room in each kindergarten was
made.
5.1. The radon concentration
In Neven, measurements were done during one week from February 12th to February 18th,
2016 (the 13th and 14th were weekend days) (Fig. 4). The measuring room was located on the ground
floor of the building; it was used during measurements, but attention was paid to the fact that air
circulation in the room is low. The measured mean value of radon is 1753 Bqm-3 (Tab. 3). As can be
seen from Fig. 4 the maximum radon concentration was detected on February 15 at 13.30 h when the
kids were sleeping, and it reached a value of 312 Bqm-3. The radon concentration was relatively high
during the few days of measurements, including weekends. Since space is not occupied on weekends,
it is worrying that the high radon concentration occurs at the beginning of the working week when the
building is occupied; on average, it is above 200 Bqm-3.
In Kolibri, radon concentration measurements were done for one week from the 3rd to the 9th of
February of 2016 (the 6th and 7th were weekend days) (Fig. 4). The measurement was carried out in a
room located on the first floor of the building. As can be seen from the time-dependent radon
measurement shown in Fig. 4, the radon concentration during the day was getting higher and reached
its maximum value on weekends. On Sunday at 23.14, the measured value reached 276 Bqm-3, while
on the next day, after ventilation of the room (the draft), there was a drop in radon concentration. The
measured mean value is 142 2 Bqm-3 (Tab. 3), while the mean value was below 100 Bqm-3 during
occupational time. Looking at the obtained results (Tab. 3, Fig. 4), it is clear that the measured
concentration significantly exceeds the global average indoor radon concentration of 46 Bqm-3, except
for the minimum concentration in Kolibri.
Figure 4. Time-dependent radon concentration (blue line) with mean value (red line):
Neven (left) and Kolibri (right)
Table 3. The results of radon measurements in two kindergartens
Maximum
concentration
Bqm-3]
Minimum
concentration
Bqm-3]
Average value
Bqm-3]
Neven
312 31
81.5 16
175 3
Kolibri
27629
38.9 12
142 2
For comparison, the indoor radon concentrations in 296 kindergartens in Sofia measured during
three months by the passive detectors (CR-39) showed an average of 132 Bqm-3 [26]. On the other
hand, a study on radon exposure in Slovenian kindergartens and schools showed that in 45
kindergartens and 78 schools, radon concentrations exceeded the level of 400 Bqm−3. After such a
finding, measures for radon level reduction were successfully performed in 35 buildings [27].
Furthermore, in Montenegro, for example, the average 9-month radon activity concentration,
measured by the CR-39 in 2855 ground-floor rooms of 468 buildings of pre-university education
(including kindergartens), was found to be 275 Bqm-3. At the same time, 728 rooms showed
concentrations above 300 Bqm-3 and 111 – above 1000 Bqm-3 [28].
5.2. The CO2 concentration
The indoor CO2 concentration (Fig. 5) and its comparison to the outdoor concentration were
analysed for the four days of measurements during the heating season from December 22 to 25, 2015
in Neven and from January 26 to 29 in 2016 in Kolibri. The analysis presented here includes only
0
50
100
150
200
250
300
350
12.02.2016
13.02.2016
13.02.2016
14.02.2016
14.02.2016
15.02.2016
15.02.2016
16.02.2016
16.02.2016
17.02.2016
17.02.2016
Radon [Bq/m3]
0
50
100
150
200
250
300
3.02.2016
4.02.2016
4.02.2016
5.02.2016
5.02.2016
6.02.2016
6.02.2016
7.02.2016
7.02.2016
8.02.2016
8.02.2016
Radon [Bq/m3]
measurements during the occupation time (08:00 to 17:00, marked with green vertical lines in Figure
5). The length of the time interval in which the indoor CO2 concentration is below the maximum
acceptable level is used as a characterization index. In both buildings, there are high concentrations of
CO2 with significantly higher average levels in Kolibri (2199 ppm) than in Neven (993 ppm) (Figure
5) during occupancy time (Tab. 4).
The outdoor daily temperature and relative humidity data were obtained from the nearby
meteorological station (Budzak – WMO code 14542). The outdoor CO2 concentration was not directly
measured but was estimated based on the indoor measurements during the weekend before and after
the reference period. As children do not stay in kindergartens during weekends, there are no sources of
CO2, and after some time, indoor CO2 concentration comes into equilibrium with the outside one due
to the diffusion process. The estimated outdoor CO2 concentration based on measurements from two
consecutive Sundays is 499 ppm for Neven and 525 ppm for Kolibri.
The CO2 concentration in Neven (blue line in Fig. 5) fulfills the BAS EN 16798-1 requirement
for category I during 62.43% of total occupancy time. At the same time, for Kolibri, it is only 5.79%
of full occupancy time (Tab. 4). The highest average air temperature measured at the height of an
average child's head (h=110 cm) during the time of occupancy in Neven leads to more frequent
opening of balcony doors/windows and the consequent inflow of external air with the lowest CO2
content (Tab. 5). These moments can be identified as the sudden declines in the indoor CO2
concentration in Fig. 5. Although the more frequent opening of the door and consequently lower
concentration of CO2 in the room can be the result of more favorable external conditions, in this case
study, the mean maximum daily outdoor temperature during the measurement period was higher
outside Kolibri than Neven. Children generate CO2 and humidity, and approximately the same number
stay in both kindergartens. Considering the lower air temperature in Kolibri, which leads to less
frequent opening of doors and windows, we can conclude why the air quality is better in Neven.
Table 4. The percentage of the total occupancy time when each building category meets the
condition
Neven
Kolibri
Total time [%]
Category I (550 ppm)
62.43
5.79
Category II (800 ppm)
75.00
14.07
Category III (1350 ppm)
97.38
31.72
Category IV (>1350 ppm)
2.62
68.28
Figure 5. The time-dependent CO2 indoor concentration in Neven (red line) and Kolibri (blue
line)
All openings, such as windows and doors, which are part of the thermal envelope, were closed,
which ensured the prerequisites for creating pressure differences between the inside of the building
and the outside air.
Table 5. The average values of the air temperature, relative humidity, and CO2 concentration by
days during time of occupancy and corresponding outdoor whole-day temperature average
values
Neven
Indoor
Outdoor
t[oC]
φ[%]
CO2 [ppm]
t[oC]
φ[%]
CO2 [ppm]
22.12.2015.
23.3
38.7
1077
6.4
79.0
499
23.12.2015.
23.2
35.6
936
5.6
79.0
24.12.2015.
23.4
37.4
1031
5.2
80.5
25.12.2015.
23.0
37.9
929
5.7
79.5
Kolibri
Indoor
Outdoor
26.01.2016.
19.8
53.7
2589
8.5
66.0
525
27.01.2016.
20
48.7
2075
6.7
74.8
28.01.2016.
20.8
50.7
1905
9.3
70.0
29.01.2016.
20.9
54.5
2227
9.6
73.5
The measurement has been performed at the pressure difference of 50 Pa between the internal
and external air. As a result, the numbers of air changes per hour of 8.78 h-1 and 2.72 h-1 were obtained
for Neven and Kolibri, respectively. The measured value for Neven is highly different from the
maximum value of n50=3 h-1 for naturally ventilated buildings [20]. The demand for airtightness is
fulfilled for the other kindergarten according to the Blower Door test results (n50 = 2.72 h-1) [20, 29].
Test points to sensitive areas such as air leaks and thermal bridges where increased air infiltration
occurs in Neven (Fig. 6). It is obvious that there are severe problems with thermal bridges around
windows (Fig. 6 - left) since the temperature of the warmest point is 22.0 °C and of the coldest one is
6.5 °C. The balcony door is shown in Figure 6 - right, and as can be seen, the hottest point has a
temperature of 19.3 °C, and the coldest one is 2.9 °C. The coldest places where intense air infiltration
occurs are at the joints of the windows, with the wall indicating the absence of sealing rubber.
0
1000
2000
3000
4000
18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06
CO₂ concentration [ppm]
Time [h]
Figure 6. Thermal image of the interior of Neven during the Blower Door test measurement
A difference in the quality of windows and balcony doors primarily causes a difference in the
measured airtightness of kindergartens. Double-glazed windows with ordinary glass and wooden
frames were embedded almost 40 years ago in Neven. In contrast, modern windows with double
thermal insulation glazing and low-emitting coating filled with argon and PVC profiles have been
recently installed in Kolibri. In addition, the facade wall has adequate thermal insulation, and thermal
bridges at the junction of the window frame to the facade wall are resolved. From the presented
analysis, it is evident that poor sealing of windows and balcony doors in Neven causes the appearance
of thermal bridges, which significantly influences the increased number of air changes, which is
almost three times higher than allowed. Although more significant infiltration is not good from the
energy demand point of view, it is evident that it is more favorable for the air quality requirement.
6. DISCUSSION
Two kindergartens have approximately the same heated volume, the number of users, and the
average time users spend in the space is eight to ten hours daily. Nevertheless, they are from different
construction periods, and other building materials were utilized. Neven is an energy-inefficient
building, but Kolibri meets the minimum energy requirements according to the Republic of Srpska
Regulations governing this area, as previously discussed.
It is essential to point out that the results presented here, specifically indoor radon
concentrations in two representative kindergartens in Banja Luka, are based on short-term
measurements. The average concentration of radon activity is found to be less than 200 Bqm-3 in both
cases. Even the highest measured radon concentration in these two buildings is less than 400 Bqm-3.
Tab. 3 shows the highest measured concentrations are around 300 Bqm-3 (slightly lower in the
Kolibri), which can be the national reference level for indoor radon concentration according to the EU
directive and WHO recommendations, as well as in current Standard EN 16798-1:2019 [17, 18, 6].
However, long-term measurements must be taken since the radon concentration varies with season and
weather conditions [30, 31].
The measured mean indoor air temperature in Neven (23.2 oC) is higher than in Kolibri (20.4
oC). Kolibri has a higher average relative humidity of 51.9 %, while Neven has 37.4%. These values
are within the comfort zone set by BAS EN 16798-1, BAS EN ISO 7730, and ASHRAE 62.1. The
measurements showed that the Neven has a higher indoor air temperature, lower relative humidity,
higher air infiltration, and lower CO2 concentration. Kolibri has a lower indoor air temperature, higher
relative humidity, lower air infiltration (better sealing), and higher CO2 concentration. However, the
radon concentration is higher in Neven, although the infiltration is better. That leads to the conclusion
that the cause might be the geology of the terrain where Neven is located. Still, special attention must
also be paid to the built-in construction materials. Natural ventilation is used to ventilate both
kindergartens by opening doors and windows and infiltration.
Indoor air quality (IAQ) measurement is based on indirect ventilation rates in two
kindergartens. The ventilation rates measured are 453 l/s for Neven and 249 l/s for Kolibri. According
to the standard BAS EN 16798-1, the recommended level of ventilation rate depends on two
components: necessary ventilation for dilution of pollution from users (biowaste) and ventilation for
dilution due to emissions from the building and the system.
If it is assumed that the required indoor air quality category is I, the recommended volume of
fresh air is 10 l/s/person and 1.0 l/s for low-polluting a building for both kindergartens. The expected
percentage of dissatisfied occupants should be less than 15. The standard requires a concentration of
350 ppm CO2 above external for energy calculation. In this case, it was obtained that the
recommended ventilation level is 342 l/s for Neven and 327 l/s for Kolibri. For calculating the
recommended ventilation levels, we used as input the following floor areas of investigated rooms in
Neven and Kolibri: 62 m2 and 77 m2, and the occupancy of 28 and 25 persons. Therefore, using a
method based on the person and the building component for the demanding level of ventilation, the
conclusion is that the ventilation rate for the new kindergarten (Kolibri) is unsatisfactory. Considering
the elevated CO2 levels in this kindergarten, it is imperative to implement proper ventilation within the
space. Additionally, in Standard EN 16798-1:2019 - Annex C, the occupancy parameters for
kindergartens are 3.8m2/person, while in Neven, it is 2.21m2/person, and in Kolibri, 3.08 m2/person
[6]. That indicates that the occupation in the mentioned kindergartens is higher than prescribed in the
EU standard.
If it is assumed that the required indoor air quality is of category II, the recommended amount of
air is 7 l/s/person and 0.7 l/s for a low-polluting building. Then, the expected percentage of dissatisfied
occupants should be below 20. In this case, it was obtained that the recommended ventilation level is
239.4 l/s for Neven and 228.9 l/s for Kolibri. The concentration of CO2 above the external for the
energy calculation is 500 ppm in accordance with the standard. Thus, according to the measured level
of ventilation, it can be concluded that both kindergartens are meeting conditions for this category.
Although higher infiltration is not good from the point of view of energy consumption, it is more
favorable in terms of air comfort and indoor air quality.
The correlation coefficients between CO2 and temperature and between CO2 and RH were
calculated for both kindergartens (Tab. 6). As seen from the table, correlations are positive, as
expected. The correlation between CO2 and RH in Kolibri is very strong (0.84), which is expected
because of its better air tightness.
Table 6. Type of correlation and correlation coefficients between CO2 and temperature and CO2
and relative humidity
Neven
Correlation coefficient
(CO2-temp)
Type of correlation
Correlation coefficient
(CO2-RH%)
Type of correlation
0.33
Weak positive
correlation
0.63
Strong positive
correlation
Kolibri
Correlation coefficient
(CO2-temp)
Type of correlation
Correlation coefficient
(CO2-RH%)
Type of correlation
0.59
Moderate positive
correlation
0.84
A very strong positive
correlation
For comparison, the measurements of CO2 concentrations in two kindergartens in Slovenia
indicated high concentrations during the winter and spring periods, while the mean concentration
during the winter in the playrooms was 1708 ppm. Furthermore, most of the measured concentrations
(89.3%) in both kindergartens exceeded 1000 ppm, and there was a significant correlation between
CO2 concentration and the number of persons [32]. In four (existing) kindergartens in Poland,
concentration values reached even 4500 ppm, and maximum values were above 3953 ppm [33].
Increased temperature, compared to recommended values for thermal comfort, was also found, with
RH values of 53% during the use of premises [33]. Furthermore, a new study in Slovenia, performed
before the COVID-19 Epidemic in 93 kindergarten spaces, showed that the average temperature was
22.6 , while the humidity was 37.1%. Maximum CO2 concentration in naturally ventilated
kindergarten was 3494 ppm, with an average concentration of 1068 ppm. Kindergarten with
mechanical ventilation had a maximum CO2 concentration of 2866 ppm, while the average was 1001
ppm. The values of all quantities during occupancy were lower in mechanically ventilated
kindergartens [34].
7. Conclusion
This research presents the first experimental results of indoor air quality parameters for
kindergartens in the Republic of Srpska. Kindergarten representatives for the year of construction,
energy efficiency (Neven-old, energy-inefficient and Kolibri-new, energy-efficient) and building
materials have been chosen. Two kindergartens have approximately the same heated volume, the same
number of users, and the same average time users spend in the space. Based on the analysis obtained
from the experimental results (radon and CO2 concentration, temperature and relative humidity of the
air, and number of air changes per hour) for individual kindergartens with respect to the values
prescribed by standards and the comparison of two buildings, few conclusions can be drawn.
The highest measured radon concentrations are around 300 Bqm-3 (slightly lower in new
kindergarten Kolibri), which can be the national reference level for indoor radon concentration
according to the EU directive and WHO recommendations, and in BAS EN 16798-1:2019.
The average measured radon concentrations for both buildings have not exceeded the level of
200 Bqm-3, but for reliable results, long-term measurement needs to be performed.
The CO2 concentration in the old kindergarten (Neven) fulfills the BAS EN 16798-1:2019
requirement for category I during 62.43% of total occupancy time, while for the new
kindergarten (Kolibri), it is only 5.79% of full occupancy time. Results of CO2 concentration
confirm that good sealing of the envelope of new buildings and user behavior (number of
users and natural ventilation) does affect air quality.
A very strong correlation is found between CO2 and RH in the new kindergarten Kolibri
(0.84), as expected due to its better air tightness. More ventilation in indoor spaces is needed
to decrease high CO2 levels. However, the positive correlation between these parameters
indicates that the introduction of outdoor air will reduce not only the CO2 level but also the
temperature and humidity of the indoor space, which can be problematic from the aspect of
thermal comfort and in the case of old kindergarten Neven it will lead to a decrease in relative
humidity below 30%, and in case of new kindergarten Kolibri, temperature reduction below
19 oC.
Using a method based on the person and the building component for the demanding level of
ventilation, the conclusion is that the ventilation rate for the new kindergarten Kolibri is 453
l/s and unsatisfactory for building category I with respect to the requirement of 327 l/s set by
standard BAS EN 16798-1:2019.
Enhancing air quality in kindergartens entails reducing the number of users per unit of surface
area and promoting appropriate user behavior, particularly emphasizing natural ventilation, like
periodic short-term cross ventilation. The final conclusion is that more attention has to be paid to
kindergartens concerning the indoor air quality requirements and additional studies, including longer-
term measurements (monitoring) of air quality parameters in the space itself and the vicinity of the
kindergarten.
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Submitted: 14.01.2023.
Revised: 24.09.2023.
Accepted: 03.10.2023.
