Impact of Material Solutions and a Passive Sports Hall’s Use on Thermal Comfort

Abstract

High outdoor temperatures and thermal gains due to solar radiation, which penetrates the interior of buildings as the climate warms up, pose a major challenge to maintaining thermal comfort in passive sports facilities. Superbly insulated and airtight envelopes, specific microclimatic requirements and very high user activity can easily lead to overheating and thermal imbalance during summer. This paper focuses on the influence of the varying thermal capacity of external walls and night-time cooling on thermal comfort in a passive sports hall building. Based on experimental studies of the thermal conditions in the building, a model of it was created in Design Builder. Through simulation, the program initially analysed the thermal conditions that arise under different envelope assemblies. Two different ways of cooling the building at night were then analysed: mechanical and natural. The results presented showed that in a well-insulated sports hall with a large volume, the type of wall material alone had only a limited influence on thermal comfort in summer. In contrast, night-time cooling in integration with the accumulation of cold in the building’s structural components had a significant impact on protection against overheating during the summer. The type of envelope material is even more important when night-time air exchange is high. Intensive natural ventilation is associated with the highest number of hours in the comfort range—28.1–32.4% more hours in relation to the variant without night ventilation. The use of mechanical ventilation, operating at night at maximum capacity, will result in an increase in the number of hours with air temperatures in the −0.5 < PMV < +0.5 range by only 14.1–21.3%. The high thermal mass of the envelope, combined with adequate ventilation, reduces the occurrence of very high indoor air temperatures, thus alleviating the nuisance of overheating. The maximum internal air temperature during the day is lower by 2.4–3.3 K, compared to the case when no night ventilation is used. Mechanical ventilation operating at its maximum capacity can reduce the maximum internal temperature by 1.2–1.6 K.

1. Introduction

Due to intensifying global warming, it becomes a significant challenge to ensure indoor thermal comfort in summer conditions [1]. The conscious and rational design of increasingly popular low-energy buildings requires appropriate solutions and the coupling of architectural decisions with the effects of their applications [2,3]. Sports facilities with specific environmental performance requirements, due to low operating temperatures and high physical activity of users, are a particular challenge. The consequence of the stringent requirements and the high insulation and airtightness of the envelope of such facilities is interior overheating during periods with high outdoor temperatures. Anthropogenic climate change is therefore driving the search for design tools to reduce the energy demand of buildings for both heating and cooling. One possibility to passively protect low-energy buildings from overheating and occupant discomfort is to exploit the accumulative properties of the thermal mass of structural materials [4,5,6,7,8].

The thermal capacity of building partitions, defined as the ability of materials to absorb and accumulate thermal energy under varying ambient temperature conditions, is dependent on the specific heat capacity and density of the materials. As the volumetric density of a material increases, the heat storage capacity of a partition built from it increases. The ability of a material to respond to changes in ambient temperature is characterised by a combination of three parameters: λ, ρ and c_p, called the thermal diffusivity coefficient or temperature equilibrium coefficient and is calculated according to Formula (1).

$$a=\frac{\lambda }{c_p\times \rho }$$

(1)

where:

a—thermal diffusivity coefficient (temperature compensation coefficient),

λ—thermal conductivity coefficient [W/mK],

c_p—specific heat capacity, [J/(kg × K)],

ρ—density [kg/m³].

Another quantity that groups the above material coefficients in a slightly different way is the material’s thermal effusivity coefficient [9,10], also known as the material’s thermal activity.

$$\mathrm{e}=\sqrt{\lambda \times \rho \times c_p}$$

(2)

where:

e—effusivity of the material [$\frac{W\times s^{\frac{1}{2}}}{m^2\times K}$],

λ—thermal conductivity coefficient [W/mK],

c_p—specific heat capacity, [J/(kg × K)],

ρ—density [kg/m³].

Numerous studies [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26] argue that thermal mass significantly contributes to a reduction in heating and cooling loads. From a thermal comfort perspective, materials with a high density and high specific heat capacity are the most desirable. There are claims in the literature that the rational use of thermal mass can reduce the energy demand for heating and cooling by up to 25–30% [27]. However, this is closely dependent on a number of factors including a building’s size, use and location, internal heat gains, the type of ventilation or, finally, the method of shading [28]. Researchers from the University of Toronto, led by M. Gorgolewski [12], carried out a series of simulations of an industrial building. They looked for the relationship between thermal mass, the thermal resistance value R of the external walls and the size of glazed surfaces. They sought to determine the critical value for the thermal resistance coefficient of external walls. There were suggestions that above a certain value of envelope thermal resistance, additional thermal mass is beneficial, while below this value, energy consumption increases, and thermal comfort is disrupted.

Detailed experimental measurements on thermal mass were carried out, among others, at Newcastle University [29]. The conclusions suggested not to rely solely on thermal resistance, as such an approach can result in erroneous expectations and inefficient design. According to the study, a static parameter such as thermal resistance is not sufficient to analyse the impact of diurnal variations in outdoor temperature and thermal mass on indoor thermal conditions. The analysis of the energy efficiency of real buildings cannot therefore, for obvious reasons, be reduced to an assessment of the thermal transmittance U alone, which ignores dynamic climatic changes in the temperate zone [29].

A team from the University of Tampere, Finland [13], carried out a detailed analysis of 28 publications on the importance of thermal mass and, on this basis, the researchers concluded, among other things, that high thermal capacity reduces the need for mechanical cooling during periods of high outdoor temperatures. In addition, the maximum indoor air temperature in a solid building can be 3–6 K lower than in lightweight buildings. The study showed that linking high thermal mass to night ventilation of office buildings can reduce the energy demand for mechanical cooling by up to 50%. It was concluded that the combination of high thermal mass and high airtightness in single-family homes can result in a 20% reduction in energy demand relative to a lightweight counterpart [16].

Using Norwegian climate data, Dokka [11] analysed the effects of night ventilation and active cooling (single-family and office building) on energy consumption and thermal comfort, for different constructions and different occupancy types. The simulation results indicated that a heavy residential building would require approximately 7% less energy for heating compared to a light building. In an office building, the disparity in heating energy requirements was up to 10%, depending on the building design adopted. In addition, it was shown that an actively cooled lightweight building required more than 30% more energy compared to a solid structure. In the case of a passively cooled lightweight building with additional night ventilation, thermal discomfort was recorded during use. The internal temperature exceeded 26 °C for 179 h in a year [11,16].

Golański [30] provides basic principles for the effective use of thermal mass. In addition to basic information on the placement and preferred thickness of thermal mass, the author clearly suggests that thermal mass should be naturally or mechanically cooled at night during the summer [30].

To determine to what extent the structural concrete of partitions stabilises the indoor climate of a building while minimising energy use, Johannesson G., Lieblang P. and Öberg M. [14,15] carried out a number of simulation studies. They analysed the energy balance in residential and office buildings for heavy and lightweight structures, located in various countries, ranging from Sweden to Portugal. The results showed that heavy construction provides a significant energy performance advantage over lightweight structures. A residential building made of heavy concrete required 2–9% less primary energy compared to a lightweight structure. This advantage increased with larger transparent surfaces on the south side. A solid structure with south-facing glazing resulted in lower energy requirements for cooling. In the case of the office building analysed, the resulting reduction in energy for cooling was used as a measure to evaluate the building. The heavier option in this case produced 10–20% better conditions compared to the lighter option.

Researchers from Tsinghua University in Beijing [18] sought to determine model thermophysical properties for the building envelope. Climatic conditions, internal and external heat sources, orientation relative to the cardinal directions, or type of ventilation were considered. The building model analysed, measuring 4.5 × 3.5 × 2.7 m, was located in Beijing, China. The south façade featured glazing measuring 1.2 × 2.4 m. Internal heat gains were estimated at 7.5 W/m², and air exchange rates at 1 h⁻¹ (closed window) and 5 h⁻¹ (open window) [18,29]. The simulation results indicated that a construction material with an enormous heat capacity of 100 MJ/m³ × K and, at the same time, a thermal conductivity coefficient λ of less than 0.1 W/mK was needed to completely reduce the energy demand for heating and cooling. The currently used insulating building materials are characterised by much lower conductivity values, but the level of the second parameter is not achievable.

With reference to the results presented in the literature, the following question arises: is material thermal storage capacity crucial in shaping thermal comfort in summer in well-insulated passive sports halls? This paper presents the results of research conducted within the framework of a finished doctoral thesis [31] and aims to show that in a very specific, low-energy sports facility with a large volume, the thermal capacity of the walls alone has only a limited effect on reducing discomfort caused by overheating.

2. Materials and Methods

2.1. Passive Sports Hall

Thermal comfort measurements were taken in a sports hall of the University of Agriculture in Krakow, constructed to passive energy standards (Figure 1). The orientation of passive buildings in relation to the cardinal directions, as recommended by The Passive House Institute in Darmstadt, involves placing the longitudinal axis of the building along the east–west direction. However, due to the shape of the plot, the University hall is oriented along the north–south axis. With a floor area of 1776.2 m², the building has a multi-purpose sports arena with seating for approximately 156 people in total, as well as a changing room and sanitary facilities with associated spaces. The main body of the building is covered by a flat roof with a 2° pitch and has a grade-to-coping height of 10.35 m. The structural layers of the walls consist of 25 cm thick silicate masonry units insulated with 30 cm thick polystyrene panels. The U-value of non-transparent external partitions is 0.1 W/m²K and that of the transparent ones is 0.8 W/m²K. The designer reports that the total solar energy transmittance g for the glazing assemblies used in the building exceeds 60% [32,33].

The eastern orientation of the building’s large glazing, with a total area of 81.9 m², resulting from the shape of the plot, entails a significant risk of overheating (Figure 2). Solar gains are to be reduced in summer by electrically controlled external shading blinds.

The building has a final energy consumption for heating of approximately 15 kWh/m²/year and a total primary energy consumption of less than 120 kWh/m²/year. The low energy requirements for heating the sports hall are ensured, among other things, by sufficiently thick, high-quality thermal insulation materials and the high airtightness of the building’s envelope n₅₀ = 0.3 h⁻¹. The building is equipped with mechanical ventilation with heat recovery. The recuperators have a maximum heat recovery efficiency of 85%.

2.2. The Criterion for Ensuring Thermal Comfort

Microclimate assessment involves measuring or calculating the magnitude of the basic and derived physical parameters, and then calculating the values of the relevant indicators for comparison with applicable standards [34] in simulation software. For temperate climates, these requirements are given in the European standard PN-EN ISO 7730:2006 [35].

The instrument used to measure the thermal microclimate in the building under analysis was the BABUC A integrated digital meter (Figure 3), which is compliant with the PN-EN 7726 standard [36]. Sensors connected to the central unit measure dry and wet bulb temperatures, indirectly mean radiant temperature, as well as relative humidity and air velocity.

The basic indicators used to analyse the thermal environmental conditions in an indoor space are: PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied), first proposed by Fanger [37]. The PMV index determines the predicted mean score according to Fanger’s seven-point psychophysical heat sensation scale [37] and takes into account a number of environmental and individual parameters that affect heat exchange rates (Figure 4).

Environmental parameters include indoor air temperature, humidity and air velocity, as well as mean radiant temperature. Individual factors related to a building’s users, which include physical activity and the thermal insulation of clothing, are extremely important for the perception of environmental conditions.

The second indicator for assessing comfort is the PPD, i.e., the predicted percentage of dissatisfaction. The PPD index, obtained from the PMV index, provides information on thermal discomfort (thermal dissatisfaction) by predicting the percentage of people likely to feel too hot or too cold in the given thermal environment. Under thermal comfort conditions, for a class with medium requirements (category II according to EN 16798-1 [38]), the PMV should be between −0.5 and +0.5, which corresponds to a PPD value of 10%.

2.3. Simulation Model in Design Builder

In this study, Design Builder software 5.0.3.7 was used to simulate the effects of internal and external shading on thermal conditions in the sports hall. It is worth emphasizing that at present, it is the most modern and most advanced tool designed for simulation calculations.

A geometrical solid model of the sports hall under study at the University of Agriculture in Krakow, Figure 5, was created using Design Builder, considering the parameters, structures and MEP services of the facility as well as occupancy schedules.

The hall was designed for 124 spectators and 32 athletes. As the research was performed during the academic year, when the facility is mainly used by student groups, the conditions were analysed in relation to active people only. The exact load on each sector of the sports hall, adopted for the validation of the model and corresponding to the use of the facility during the measurements, is presented in

Table 1. Load on the University of Agriculture sports hall during the second measurement round (adopted for model validation).

Date	Hours	Number of Occupied Sectors	Approximate Number of People in the Room/h
20 May	11.00–14.00	2	50
	14.00–16.30	1	25
	17.30–22.00	2	15
21 May	8.00–10.00	2	50
	10.00–11.00	1	25
	11.00–15.30	2	50
	15.30–17.00	0	0
	17.00–18.00	1	25
	18.00–19.00	2	50
	19.00–20.00	1	10
22 May	8.30–10.00	1	25
	10.00–11.00	2	30
	11.30–13.00	3	75
	13.00–14.30	1	25
	14.30–16.00	0	0
	16.00–18.00	2	30
	18.00–20.00	2	50
	20.00–22.00	1	15
23 May	8.00–11.00	1	25
	11.00–12.00	2	30
	12.00–16.00	0	0
	16.00–19.00	3	50
	19.00–20.00	1	10
	20.00–22.00	3	75
24 May	9.00–15.00	3	50

.

The metabolic energy of the exercising student was assumed to be 300 W/person. The metabolic rate value taken from the Design Builder library corresponds to the activity of a person practicing “exercise/sport”. For the summer period analysed, a clothing thermal resistance value corresponding to lightweight sportswear of 0.3 clo was used.

In the validation, it was assumed, based on the actual use of the hall during the measurements, that the window blinds on the south-east elevation were shut from the early morning hours. Although the blinds were lowered, they did not completely restrict access to light, as the aluminium slats were inclined at approximately 30° to the window surface. On the northwest side, the blinds were not used at all during the measurement period.

The required illuminance in the hall was assumed to be 400 lux as per the relevant standard [39]. Artificial lighting switched on automatically when natural lighting was insufficient during the hall’s opening hours.

A basic simulation algorithm option called Simple was used to model the mechanical ventilation system in Design Builder. In the design documentation of the building, the capacity of the air handling unit was assumed as dependent on use:

• during a competition and with full stands—100%,
• 1/3 of the room used—20%,
• 2 or 3 spectator sectors occupied—40 or 60% of maximum capacity [32].

The maximum capacity of the air handling unit corresponds to an air exchange rate of 0.75 ac/h (maximum ventilation capacity is 9.000 m³/h, room volume is 12.075 m³) [32].

The hall envelope’s high airtightness was confirmed by a pressure test in accordance with EN ISO 13829-2002 [40]. The result was n₅₀ = 0.3 h⁻¹. The model assumed a conventional determination of the airtightness of the sports facility at a level defined as Excellent.

During the validation of the model used for simulation, the effects of air infiltration and natural ventilation were taken into account according to the actual use of the building. An interview was to establish that no fixed schedule for window tilting was in place. It was dependent on subjectively determined needs and individually controlled by class attendees. For the validation of the model, based on the information sought, window opening times were set as shown in

Table 2. Window opening times assumed in the modelling on the southeast and northwest sides of the University of Agriculture hall.

Date of Measurement	Windows on the Southeast Facade	Windows on the Northwest Facade
20 May	tilted 7.00–21.00	tilted 8.00–21.00
21 May	closed	closed
22 May	tilted 14.00–20.00	tilted 19.00–20.00
23 May	tilted 8.00–12.00 and 16.00–21.00	tilted 19.00–22.00
24 May	tilted 8.00–20.00	tilted 9.00–18.00

.

The building’s design provided for night-time ventilation, functioning by opening windows on opposite walls of the sports arena. According to the nomenclature adopted by the design’s authors, it was achieved via natural cross-ventilation. However, it is known that this option was not used during the measurement period.

The validation of the hall model was complex and hampered by uncertain information about the use of the facility. The authors were not in the hall for the entire five-day measurement period and the data obtained were based on an interview with hall staff. The original findings, adopted to create the initial model in Design Builder, were at times significantly different from measurements. Only strenuous modifications (about 70 steps), in consultation with the hall staff, regarding the number of hall users and window tilting allowed for a convergence of the data and simulation results.

To determine the correlation between the measurements and the simulation, a correlation coefficient was calculated. Comparing the results of indoor air temperature measurements in the hall from 20–24 May with the results of the final model, a correlation coefficient value of 0.94 was obtained (Figure 6).

A correlation coefficient value in the range of 0.7 r_xy < 0.9, indicates a very high correlation in statistical analysis [41]. Therefore, the model of the passive sports hall in Krakow made in Design Builder can be used for further analyses.

The standard deviation was calculated, and the differences between the indoor air temperature curves from measurements and simulations were plotted as a bar chart (Figure 6). The resulting standard deviation value of 1.138 indicates a slight dispersion of the variables around the arithmetic mean value of the test variable.

3. Results of Thermal Comfort Analysis

3.1. Experimental Analysis and Survey

The first trial measurements in the facility (without users) were carried out in the period between 7 and 10 August. Another round of measurements was performed the following year between 20 and 24 May, during which the hall was used for sports activities. Each time the outdoor temperature was above 30 °C. The first time, 663 readings were taken over three days, and the second time, 1279 measurements were taken over five days. It should be noted that the facility was not in use during the first series of measurements, so it was possible to carry out continuous tests and leave the measuring equipment unattended and secured in a central area of the arena. The artificial lighting and mechanical ventilation system was switched off during this period and all windows were closed. In this sense, the conditions tested did not correspond to the normal operation of this building, but characterise the natural (undisturbed by the operation of the service) insulating and capacitive properties of the envelope.

The second series of measurements was carried out under conditions compatible with the intended use of the sports facility, which was used throughout the study period. The detailed loading of the individual sectors of the sports hall is given in Table 1.

The mechanical ventilation system was only activated on the second and third days of measurement, i.e., on 21 and 22 May, only when there were people in the hall (Table 1). The windows were opened and closed manually during the tests, during the hours of use of the facility, from 8.00 to 10.00. During the microclimate tests carried out in the hall, the natural night-time ventilation, as assumed in the design, was not used.

For safety reasons, the meter was located behind a baffle and shielded by a net during the measurements (Figure 7). The short distance from the baffle meant that its effect on the average radiation temperature was overestimated.

Selected indoor environmental parameters for the hall during the study are shown in

Table 3. Average measured values of indoor environmental parameters in the UR hall.

Environmental Parameters (Average Values)	Unit	First Measurement Series	Second Measurement Series
Indoor air temperature ta	[°C]	27.9	24.1
Indoor air humidity	[%]	58.28	50.85
Radiation temperature tr	[°C]	28.8	24.30
PMV	[-]	1.14	2.26
PPD	[%]	33.15	84.18

.

The indoor air temperature ta, during the first measurement period, ranged between 26.9 °C and 29.0 °C, while the average value was 27.9 °C (Table 3). The trend line shown in Figure 8a illustrates the increase in mean indoor air temperature as a result of energy accumulation from day to day. The average value of the radiation temperature of the surrounding surfaces was 28.8 °C, while the average relative indoor air humidity was 58.28% (Table 3).

The mean PMV value (Table 3) was 1.14, but even the minimum value (0.76) was outside the thermal comfort range (Figure 8b). The reason for the observed sudden morning spikes in PMV values (Figure 8b) was the direct solar radiation that reached the meter’s sensors through the unprotected windows on the west side with blinds and the glazing in the emergency door. During the entire monitoring period, the internal thermal conditions were outside the comfort zone. The average PPD value was higher than 30% (Table 3), and the maximum instantaneous value even exceeded 90%.

During the first measurement period, the conditions inside the facility did not produce thermal comfort, not even for a moment. This was not only due to climatic conditions, but also to a large extent to the way the facility was operated during this period. Mechanical ventilation and natural ventilation were not used, and windows were not opened.

During the second series of measurements in May, the average indoor air temperature was 24.1 °C, while the maximum value exceeded 27 °C (Figure 9a). The minimum indoor temperature was 22.1 °C (Figure 9a). Figure 9a, on 21 May, shows a decrease in the indoor temperature (around 16:00–17:00) and a renewed increase from 17:20, related initially to the break in classes and then to the heat load of the hall’s users (Table 1). On 23 May, the indoor air temperature did not increase compared to the previous day, as a result of the lower number of people in the hall in the morning (lower internal gains). In addition, between 12:00 and 16:00, when the hall was not in use, the windows were closed, which protected the building from additional gains from warm outside air. However, it can be seen from the distribution in Figure 9a that the trend line, as before, shows a strong tendency for the temperature values to increase on consecutive days.

On 24 May, during the use of the building by a significant number of people between 9:00 and 15:00, the indoor air temperature rose rapidly, and the highest value was 27.3 °C (Figure 9a). These conditions were influenced by additional heat gains from the outside air, due to the windows on both sides of the space being open all day, and thermal gains from the presence of users. The mean value of the radiation temperature of the surrounding surfaces, however, was significantly lower, at 24.3 °C. The average relative indoor air humidity was 50.85% (Table 3).

During the entire measurement period in May, internal thermal conditions were far outside the thermal comfort zone (Figure 9b). The PMV value did not fall below 1.6 and its maximum value exceeded 3.0 (Figure 9b). From the third day of the second series of measurements onwards, the PMV value exceeded the permissible value of 2.0 throughout the range.

The unfavourable microclimate in the hall was not only caused by the high outside air temperature, but was also due to the way the building was operated at the time of the measurements. Initially inoperative and then poorly used mechanical ventilation and the lack of regular ventilation at lower outside temperatures led to the accumulation of excess energy in the hall.

3.2. Survey Results

In addition to thermal comfort measurements, an original survey was conducted in the hall among 104 randomly selected users of this building. Essential information about the respondents is shown below:

• 9 men and 95 women—average physical activity,
• age of respondents: 19–23 years old,
• height of the respondents: 160–185 cm,
• clothing: light, shorts/leggings and t-shirts.

The results of the questionnaire on the environmental conditions inside the hall are presented in

Table 4. Results of the May 2014 survey on environmental conditions in the University of Agriculture sports hall.

Fanger Scale	How Would You Rate the Temperature in the Hall?
	Woman	Man
+3 (hot)	30	-
+2 (warm)	35	3
+1 (quite warm)	19	1
0 (neutral)	11	5
−1 (quite cool)	-	-
−2 (cool)	-	-
−3 (cold)	-	-

. The majority of the respondents opted for the ‘warmer’ side of the Fanger scale (88/104 of those surveyed). Only 16 of the respondents (15% of those surveyed) described the microclimate in the hall as neutral to them, meaning that they experienced thermal comfort. As many as 30 (28.8%) respondents rated the thermal condition inside the hall as ‘hot’, i.e., the maximum on the scale presented. The ‘warm’ rating was given by 38 people, and the ‘quite warm’ by nearly 20.

The PMV values for both measurement periods were outside the thermal comfort limits. According to international standards and common practice, temporarily exceeded limits are usually accepted provided that the internal microclimate does not endanger the health of the user. The high physical activity of sports hall users, the low insulation value of clothing and the short periods of use preclude the use of an adaptive comfort model. Physiological or psychological adaptation to indoor conditions is impossible if the sports facility is used for several hours a week.

The short-term measurements carried out in the hall and the survey are not sufficient measurements to assess the building. They are an indication that in buildings with very low energy consumption, overheating of the interior often occurs during the summer months. The surveys carried out over a few days are therefore a sufficient basis for confirming the existence of the problem and for further simulation analyses of the studied building.

3.3. Simulation Variants and Results

Due to the specific use of the building only during the academic year, simulations were carried out for the period from 1 May to 30 June. The other summer months were not included due to the holiday period. In the simulation model, the layout of the layers in the external wall assembly was adopted according to the design assumptions: external silicate plaster and adhesive layer reinforced with mesh with a total thickness of 1 cm, thermal insulation—Platinum polystyrene (EPS 031 Termonium Plus) 30 cm, hollow silicate masonry units 25 cm, internal mineral plaster 1 cm [32]. In the subsequent simulation variants, only the structural layer was modified, without changing the other materials. The structural layer thickness of 25 cm assumed in the design was left in place for all options. Although for some variants this assumption deviates far from the actual needs and feasibility, it will allow a simple comparison of the impact of material properties on thermal comfort. The material characteristics are summarised in

Table 5. Characteristics of the construction materials adopted for the analysis according to [20,42,43,44].

Construction Material	Density ρ [kg/m3]	Thermal Conductivity λ [W/(m × K)]	Specific Heat c [J/(kg × K)]	Thermal Capacity C [MJ/m3 × K]	Thermal Diffusivity (Temperature Compensation Coefficient) a [m2/s]	Material Effusivity e [(W × s1/2)/(m2 × K)]
Concrete	2200	1.3	840	1.85	7.03 × 10−7	1549.97
Aerated concrete	600	0.21	840	0.50	4.17 × 10−7	325.33
Clinker brick masonry	1900	1.05	880	1.67	6.28 × 10−7	1324.99
Solid brick masonry	1800	0.77	880	1.58	4.86 × 10−7	1104.39
Natural stone	2800	3.5	920	2.58	1.36 × 10−6	3002.67
Hollow-core silicate masonry units	1500	0.46	880	1.32	3.48 × 10−7	779.23
Silicate masonry units	1900	0.9	880	1.67	5.38 × 10−7	1226.70
Reinforced concrete	2500	1.7	840	2.10	8.10 × 10−7	1889.44

.

When considering the characteristics of the construction materials adopted for the analysis, it is important to note the values obtained for the temperature equalisation coefficient a. The highest value of the coefficient is found in natural stone (1.36 × 10⁻⁶ m²/s), which has a conductivity coefficient of 3.5 W/mK, Figure 10. This means that a material with a high thermal capacity and conductivity reacts very slowly to fluctuations in external temperature. Reinforced concrete and plain concrete also have relatively high a-values, in contrast to aerated concrete, for example.

In all options for the simulation analysis, the settings (ventilation, lighting, blinds, people) were assumed to be as close as possible to the actual operation of the arena. It was assumed that window opening is possible throughout the day between 8:00 and 22:00 on both sides of the arena (20% of the total opening). In the simulation, however, the daily ventilation was made dependent on the external conditions. If the condition T_out > T_int is met—the windows are closed, where:

• T_out—outdoor air temperature [°C],
• T_int—indoor air temperature [°C].

No account was taken of night ventilation, and the assumed minimum indoor air temperature during window tilting is 14 °C. It was assumed that the blinds on the south-east elevation are lowered when the solar irradiance exceeds 100 W/m², and on the north-west side, the blinds are uncovered throughout the simulation period, which is not in accordance with the design assumptions and common sense, but corresponds to the actual use of the building.

The required illuminance in the hall was assumed to be 400 lux in accordance with PN-EN 124641:2012 [39]. Artificial lighting is used as required during the hours of use of the hall, i.e., 8:00 to 22:00. On the basis of additional simulations it was determined that, despite the lowered blinds on the south-east side in the morning and afternoon, artificial lighting is only needed after 19:00.

The assumed use of the room during the week is shown in

Table 6. The use of the University of Agriculture sports hall adopted for the simulation.

Day of the Week	Hours	Number of People in the Hall/h
Monday–Friday	8:00 to 16:00	50
	16:00 to 22:00	25
Saturday–Sunday	9:00 to 20:00	50

.

The following simulation options were adopted:

• Variant 1—external wall layering: external silicate plaster and adhesive layer reinforced with 1 cm thick mesh, thermal insulation—polystyrene Platinum 30 cm, plain concrete 25 cm (with parameters as in Table 5), internal mineral plaster 1 cm.
• Variant 2—aerated concrete in the construction layer with parameters as per Table 5.
• Variant 3—clinker bricks in the construction layer with parameters as in Table 5.
• Variant 4—solid bricks in the construction layer with parameters as in Table 5.
• Variant 5—natural stone in the construction layer with parameters as in Table 5.
• Variant 6—hollow silicate masonry units in the construction layer with parameters as in Table 5.
• Variant 7—solid silicate masonry units in the construction layer with parameters as in Table 5.
• Variant 8—reinforced concrete in the structural layer with parameters as in Table 5.

The Polish building regulations do not provide clear guidance on the temperature range for thermal comfort in sports facilities [33] (Section 4, §134). Regulations specify a design temperature, used in gymnasium design, of 16 °C. However, there are no clear guidelines on the range of thermal comfort for athletes. In publications on thermoregulation, it can be found that, for example, activity at a heart rate of 140–150 beats/min is best performed at 16–17 °C. Increasing the heart rate to 170–180 beats/min is associated with a reduction in the temperature comfort zone to 13–14 °C. In the available sources, there is a lack of clearly defined sports categories, metabolic values and corresponding thermal comfort temperatures. An in-house analysis of indoor conditions for an assumed metabolic level and clothing insulation made it possible to establish (using an algorithm formulated by Fanger) an indoor thermal comfort range. Ultimately, it was assumed that for active users of the hall, comfortable indoor air temperatures in summer are in the range 14–18 °C.

Table 7. Mean and maximum values of indoor air temperature and radiation temperature for the two-month analysis period and the eight simulation variants adopted.

Construction Material	Indoor Air Temperature ta [°C]			Radiant Temperature tr [°C]
	Average	Maximum	Average	Maximum
Concrete	19.8	26.0	20.8	25.7
Aerated concrete	20.0	27.2	21.0	27.0
Clinker brick masonry	19.8	26.1	20.8	25.8
Solid brick masonry	19.9	26.3	20.8	26.0
Natural stone	19.8	25.6	20.8	25.3
Hollow-core silicate masonry units	19.9	26.5	20.9	26.2
Silicate masonry units	19.9	26.2	20.8	25.9
Reinforced concrete	19.8	25.9	20.8	25.6

summarises the calculated arithmetic mean and maximum values of the indoor air temperature and radiation temperature in the UR hall for the assumed eight simulation variants. The variant with aerated concrete has the highest instantaneous indoor air temperature value of 27.2 °C. In contrast, the lowest maximum temperature of 25.6 °C applies to the structural layer containing natural stone. The average indoor air temperature values for all variants are close to or equal to 19.9 °C. In terms of radiation temperature, the average values for all assumed options are very close to each other and fluctuate around 20.8 °C. Differences in the maximum radiation temperature values are noticeable and amount to 1.3 °C. As with the indoor air temperature, the highest maximum radiant temperature applies to the aerated concrete wall structure (27.0 °C) and the lowest to the natural stone bearing layer (25.3 °C).

The results obtained in this way for a two-month period indicate very little influence of the varying heat capacity of the external walls (for the assumed conditions of use of the building). The differences between the maximum indoor air temperatures are in the range of 0.1–1.6 °K.

In order to better illustrate the behaviour of the thermal mass, the following section shows the air temperature distributions in the hall during selected short periods of high and low outdoor temperatures (Figure 11 and Figure 12).

During a week of high outside temperatures, the difference between the air temperatures is between 0.1 and 2.0 °K for the individual material variants. The greatest difference occurs on 23 May at 18:00 and is 2.0 °K (between a natural stone wall and an aerated concrete partition). The highest temperature values can be observed for lightweight aerated concrete structures, for which the difference between the air temperature and the upper limit of the thermal comfort range is almost 8 °K. Analysing the hot five-day period, it can be seen that the upper limit of the comfort temperature range of 18 °C assumed for the hall is exceeded (by 1.0 to 7.8 °K) in each material variant.

According to the conclusions of thermal mass studies carried out around the world, lightweight material reacts fastest to changes in outdoor temperature. In the case of high outdoor air temperature values, a partition made of a material with low thermal mass will be the least desirable in terms of protecting the interior from overheating. The average and maximum values for the indoor air temperature over a hot five-day period in

Table 8. Mean and maximum values of indoor air temperature for the five-day period of high outdoor temperatures (20–24 May).

Construction Material	Indoor Air Temperature ta [°C]
	Average	Maximum
Concrete	22.1	25.0
Aerated concrete	23.0	25.9
Clinker brick masonry	22.2	25.1
Solid brick masonry	22.3	25.2
Natural stone	21.9	24.6
Hollow-core silicate masonry units	22.5	25.4
Silicate masonry units	22.3	25.2
Concrete	22.1	24.9

confirm the slightly more favourable properties of natural stone compared to aerated concrete in terms of protection against overheating.

When considering the period of low external temperatures (Figure 12), it can be seen that the variant with lightweight aerated concrete has the lowest internal air temperature values. On the other hand, the highest temperatures can be observed in the variant with natural stone, i.e., a material with a high heat capacity value and high thermal conductivity. Due to the nature of the object under analysis and the low temperature values of the comfort zone, it can be seen in Figure 12 that the range of temperature changes for the lightweight material overlaps more with the comfort zone. This is related to the different thermal resistance of the wall in the different variants. The materials of the construction layer differ considerably in their thermal conductivity although they have the same thickness. The result is a variation in resistance and associated heat loss through the hall cladding. The period under analysis (May and June) is characterised by large diurnal fluctuations in outdoor temperature. Hence, during the numerous cool days during this period (

Table 9. Number of hours for different outside air temperature ranges for the entire analysis period.

Number of Hours with Outdoor Air Temperature < 10 °C	Number of Hours with Outdoor Air Temperature within 10–15 °C	Number of Hours with Outdoor Air Temperature within 15–20 °C	Number of Hours with Outdoor Air Temperature within 20–25 °C	Number of Hours with Outdoor Air Temperature > 25 °C
226	484	450	239	65

), increased thermal losses can reduce indoor comfort. Conversely, during the hot period, the capacity for effective accumulation is not properly utilised, due to the lack of night-time interior cooling.

As a result, despite the markedly different properties of the materials used, very little variation is obtained in the results of the predicted mean evaluation index over a two-month period (

Table 10. Hourly distribution of PMV for the adopted simulation variants and the two-month calculation period.

Construction Material	Number of Hours with −0.5 < PMV< +0.5	Number of Hours with PMV > 0.5
Concrete	684	780
Aerated concrete	669	782
Clinker brick masonry	681	783
Solid brick masonry	673	791
Natural stone	678	786
Hollow-core silicate masonry units	676	788
Silicate masonry units	675	789
Concrete	675	789

).

Figure 13 illustrates the distribution of the PMV for the five-day average of high outside temperatures. As in the case of indoor air temperature, the highest PMV values are found in aerated concrete construction and the lowest in natural stone.

The results obtained for the long period (Table 10) are due to the large diurnal temperature fluctuations in the spring and summer months analysed, the specific way in which the building is used and the form of the wall material variants (same thickness of the structural layer).

Analysing the five-day period of high outdoor temperatures, it can be seen that the natural stone variant has the highest number of hours (18 h) during which thermal comfort conditions prevail (

Table 11. Hourly distribution of PMV for the adopted simulation variants and the five-day (20–24 May) calculation period.

Construction Material	Number of Hours with −0.5 < PMV < +0.5	Number of Hours with PMV > 0.5
Concrete	17	103
Aerated concrete	6	114
Clinker brick masonry	14	106
Solid brick masonry	9	111
Natural stone	18	102
Hollow-core silicate masonry units	9	111
Silicate masonry units	11	109
Concrete	17	103

). Materials with a high thermal capacity (natural stone, reinforced concrete, concrete) are characterised by better thermal conditions on hot days compared to others. The worst performer is the variant with lightweight aerated concrete, for which, during 6 h of all 120 h, the PMV value is in the range of −0.5 < PMV < +0.5.

Intensive cooling of the massive interior during the night is one of the best known and at the same time simplest ways to protect buildings from overheating. In the analysed building, no such treatment was found, although it was recommended in the technical design of the building. Therefore, for the exterior wall material variants previously adopted for analysis, the effect of night cooling on thermal comfort was checked using Design Builder. In the simulation analyses, two different methods of night cooling of the building were considered: mechanical or natural ventilation. In the simulation results presented below, there are also references to a variant without night cooling. Although such a way of using the building in summer is not rational, its consideration is based on the actual use of the hall.

In modelling the hall, it was determined that the minimum required fresh air flow per player is 30 m³/h [45]. For 50 people playing, an air exchange of 1.500 m³/h will meet the hygienic needs of the users. The minimum fresh air flow during the day must be provided by mechanical ventilation in a situation where the building has no windows open and no natural ventilation. The maximum capacity of the air handling unit designed for this building corresponds to an air exchange rate of 0.75 ac/h (the maximum ventilation capacity is 9000 m³/h, and the volume of the hall is about 12075 m³). In the case of mechanical ventilation at night (23:00 to 6:00), the intensity of air exchange was assumed at 20% of the maximum value, and then 100%. Night-time natural ventilation was implemented in the simulations in the form of window tilting (40% opening) from 23:00 to 6:00, throughout the analysis period. The actual air exchange with the windows tilted during the night is calculated by the program depending on the current climatic conditions, i.e., outdoor temperature and wind direction and speed.

During the day, the windows can be tilted between 8:00 and 22:00 according to the actual use of the hall and depending on the external conditions (with the condition T_out > T_int—windows closed). The value of the minimum temperature of the indoor air during the tilting of windows during the day and night is 14 °C, its achievement is associated in the simulation algorithm with the closing of windows.

Table 12. Maximum indoor air temperature values for the two-month analysis period without night ventilation and with night cooling applied.

Construction Material	Maximum Indoor Air Temperature [°C]
	No Night-Time Cooling	With 20% Night-Time Cooling	With 100% Night-Time Cooling	Natural Night-Time Cross-Ventilation
Concrete	26.0	25.5	24.6	23.4
Aerated concrete	27.2	26.8	25.6	23.9
Clinker brick masonry	26.1	25.7	24.7	23.4
Solid brick masonry	26.3	25.8	24.7	23.5
Natural stone	25.6	25.2	24.4	23.2
Hollow-core silicatemasonry units	26.5	26.0	24.9	23.6
Silicate masonry units	26.2	25.7	24.7	23.4
Concrete	25.9	25.4	24.6	23.3

summarises the results of calculating the maximum indoor air temperature for all three night-time ventilation scenarios for the building and for all eight exterior wall material variants.

Again, it should be noted that the differences caused by the type of wall material, within the same night ventilation method, are small. When mechanical ventilation was used at night to cool the body of the building, operating at 100% efficiency, the difference in the value of the maximum indoor air temperature between the extreme variants was only 1.2 °K. When natural ventilation, which induces less intensive air exchange than mechanical ventilation, was used at night, the differences between the adopted eight variants were even smaller, amounting to a maximum of 0.7 °K. As before, slightly lower values of maximum indoor air temperature were observed for materials with high thermal capacity (natural stone, reinforced concrete) compared to lightweight materials (aerated concrete). Therefore, it can be concluded that in the case of a building with a large volume, the type of construction material used and the associated thermal capacity of the interior are only of limited importance in shaping thermal comfort in spring and summer.

The air exchange rate during the night was significant for thermal conditions in the building interior throughout the analysis period. With mechanical ventilation operating at the design recommended minimum level (20%), the maximum indoor air temperature for all variants was lower by only 0.4–0.6 °K compared to the variant without night-time ventilation. Mechanical ventilation operating at its maximum capacity guaranteed a reduction in the maximum indoor temperature by 1.2–1.6 °K. If natural ventilation of the building at night had been used, maximum temperatures would have been lower by up to 2.4–3.3 °K with respect to the variant without night-time ventilation.

As before, a five-day period of high outdoor temperatures was selected for detailed analysis. Figure 14 and Figure 15 compare the resulting indoor air temperature values for two extremes in terms of the heat capacity of materials. Opening windows at night results in a reduction in daytime indoor air temperature (e.g., at 14:00) of 2.2–3.3 °K for aerated concrete and 2.0–2.5 °K for natural stone compared to the variant without night-time ventilation. The use of mechanical ventilation at night (0.75 ac/h) on the analysed days of 20–24 May reduced interior temperature values to a lesser extent than natural ventilation. This is due to the higher intensity of natural air exchange compared to the possibility of mechanical ventilation. The stone wall cooled naturally at night, and was characterised by interior air temperature values closer to the comfort zone (Figure 15).

Table 13. Number of hours with conditions in the thermal comfort range −0.5 < PMV < +0.5 for the analysed variants without night ventilation and with night cooling applied.

Construction Material	Number of Hours with Conditions within the Thermal Comfort Range−0.5 < PMV < +0.5
	No Night-Time Cooling	With 20% Night-Time Cooling	With 100% Night-Time Cooling	Natural Night-Time Cross-Ventilation
Concrete	684	742	842	975
Aerated concrete	669	712	779	930
Clinker brick masonry	681	740	835	980
Solid brick masonry	673	733	825	966
Natural stone	678	740	862	992
Hollow-core silicate masonry units	676	728	811	952
Silicate masonry units	675	734	828	982
Concrete	675	741	847	998

summarises the number of hours in the thermal comfort range (the condition 0.5 < PMV < +0.5 is met), for the considered variants of night-time cooling and eight different building materials. Significant differences appear with changes in the intensity of night-time ventilation. When natural night-time ventilation, the most effective in this hall, is used, the number of hours in the thermal comfort range increases by 28.1–32.4% compared to the option without night-time cooling. The use of mechanical ventilation, operating at night at maximum capacity, increased the number of hours in the thermal comfort range by 14.1–21.3%. It should also be noted that the use of maximum-capacity mechanical ventilation involves additional costs, associated with significant energy consumption.

To graphically illustrate the effect of night-time cooling on thermal comfort, Figure 16 and Figure 17 show the distribution of predicted average rating index values for selected construction materials—aerated concrete and natural stone. As before, a five-day period with the highest outdoor temperatures was selected from the two-month interval analysed. The PMV values, for neither of the analysed options, coincide completely with the thermal comfort zone. However, the graph that takes into account natural night-time ventilation runs closest to this zone, in both cases. In the case of structural walls made of stone and natural cooling, at night for most hours, the PMV value ranges from −0.5 to +0.8, which, according to the Fanger scale, means comfortable or indifferent conditions for hall users (Figure 17). The use of lightweight aerated concrete in the structural layer causes the distribution of PMV values to fall within a wider range of −0.4 to +1.1, despite the natural ventilation with cool air at night (Figure 16). The black graph (the variant without night-time cooling) has little overlap with the thermal comfort zone in both cases of the materials used. This means that those using the facility will be clearly too warm during this time. The use of mechanical ventilation for night-time cooling (orange graph) lowered PMV values, but due to its limited rate, it was not as effective as natural ventilation.

To complete the information on the sports arena of the University of Agriculture, it is necessary to mention the modification of the ventilation system, which the authors learned about after the measurements were taken. In view of the building’s repeated overheating in summer and the great discomfort felt by users, a mechanical cooling system was installed in the arena. The decision to upgrade confirmed the problem of the lack of thermal comfort during high outdoor temperatures noted during the survey (2013 and 2014).

4. Discussion

In passive buildings, protection against overheating is crucial and should be an essential step in the design process. The choice of specific solutions must be well thought out and preceded by a thorough analysis of both the efficiency of a given system, as well as its energy consumption and implementation costs. Trying to minimise total energy consumption and maintain thermal comfort conditions without mechanical cooling is very difficult to achieve. In the design and construction documentation of the analysed sports hall, air conditioning was not provided. Among the available passive tools, the authors looked for effective methods to reduce overheating.

Sports facilities are spaces with specific microclimatic requirements due to the required operating temperature and physical activity of users. Ensuring thermal comfort is particularly important there, as it can affect the performance and health of athletes. Most sports facilities are multi-purpose arenas, where several activities with different metabolic rates are performed. Determining a comfortable thermal environment for all athletes and spectators is difficult and can lead to an overestimation of thermal sensation in some athletes. This article examines conditions for lower-activity athletes.

In the context of overheating and reducing thermal discomfort on hot days, materials with a high effusivity factor are more desirable. However, in the case of well-insulated low-energy buildings with a very large volume and a small number of partitions (such as the UA sports hall), their thermal capacity is not the main factor that affects thermal comfort in summer. Night-time ventilation is key to preventing overheating. It is known that the thermal component of the natural air exchange mechanism functions most effectively on cooler days and nights. The difference in indoor and outdoor air temperature creates a difference in density and pressure, which in turn translates into air circulation through natural convection. The pressure difference, and thus the ventilation rate, is proportional to the temperature difference between the indoor and outdoor air. Given the thermal capacity, the effects of material variation are greater the more intensive the night-time ventilation of the interior and the associated nightly cooling effect of the interior. The analysis shows that the effects of night-time mechanical ventilation of a large-volume hall are weaker compared to natural night-time ventilation. This is due to the relatively low power of mechanical ventilation relative to the total volume of the interior. The intensity of mechanical ventilation was related to the expected number of users, not the interior volume. The maximum capacity of mechanical ventilation corresponds to a volumetric air exchange of 0.75 h⁻¹. Night-time natural ventilation is more effective in discharging thermal mass due to an average number of air exchanges of about 4 h⁻¹. Analyses of the effect of night-time cooling on thermal conditions in passive buildings have also been the subject of separately published articles [46,47].

The unfavourable orientation of the analysed building, as well as the effectively insulated shell, caused a significant increase in internal temperature during the study period. Night-time ventilation is used sporadically in the hall building due to various practical considerations: automatic closing of windows in windy or rainy conditions and fear of burglary. Without close cooperation between designers and users on how to discharge excess stored energy in summer, advanced passive buildings will not be able to protect consumers from discomfort.

It is worth mentioning that the adaptive comfort model is increasingly often used to assess thermal conditions in buildings with hybrid ventilation. In the model, during a long period of rising outdoor air temperature, the human body adapts slowly to these conditions and the range of comfortable conditions shifts towards higher temperatures. This type of approach can only be used if a building’s occupants are able to adjust their clothing or open the windows in response to changing environmental conditions. By accounting for occupant adaptation, a more lenient assessment of the microclimate makes it possible, once relevant requirements have been met, to accept conditions treated as overheating under Fanger’s criterion. Although the adaptive method of determining thermal comfort has its limitations, it should be used wherever possible. The synergy of an indoor environment controlled by the occupants in response to the prevailing outdoor conditions and the low energy consumption of passive buildings is becoming an indispensable part of sustainability. By factoring in the thermoregulatory capabilities of the body and using the basic principles of heat exchange with the environment, it is possible to ensure occupant comfort with minimal operating costs.

5. Conclusions

Based on the analysis of the impact of material solutions and night-time ventilation on thermal comfort in a passive sports hall, the following conclusions can be made:

• Night-time cooling can have a large impact on protection against overheating in passive buildings during summer. Intensive natural ventilation is associated with the highest number of hours in the comfort range: 28.1–32.4% more hours compared to the variant without night-time ventilation. The use of mechanical ventilation, operating at night at maximum capacity, will result in an increase in the number of hours with air temperatures in the −0.5 < PMV < +0.5 range by only 14.1–21.3%.
• In the case where natural ventilation was used at night the maximum indoor air temperature during the day was lower by 2.4–3.3 °K, relative to the case where no night-time ventilation was used.
• With mechanical ventilation operating during the night at its design-recommended minimum level (20%), the maximum internal air temperature is only 0.4–0.6 K lower than without night ventilation. Mechanical ventilation operating at its maximum capacity can reduce maximum indoor temperature by 1.2–1.6 K.
• In the hall under study, the design of the ventilation system addressed the necessary hygienic air exchange resulting from the maximum number of users (maximum 0.75 ach). The design of the facility, taking into account thermal comfort, should allow much more intensive forced air exchange, even several exchanges during the hour [46].
• One important advantage of mechanical ventilation is its independence from external conditions, certainty of operation and adjustability. However, its significant cost and additional energy consumption is a downside.
• Natural ventilation depends directly on climatic conditions, poses problems of safety, protection from flooding, wind damage to windows, etc.
• In the case of a well-insulated sports hall with a very large volume, the thermal capacity of exterior wall materials has little effect on improving thermal conditions. It is not significant in shaping thermal comfort in summer. This is due to the low volume of wall materials in relation to the much greater volume of this building. In the case of residential or office buildings with small rooms, these proportions are different and the influence of the volume of the partitions can be much greater.
• Solid materials (natural stone, reinforced concrete), with high values of effusivity coefficient and temperature equalisation, allow slightly better results than lightweight materials with lower thermal conductivity.
• The high thermal capacity of the envelope reduces the occurrence of very high air temperature values inside the building, thus reducing overheating.
• The type of partition material is all the more important the greater the night-time air exchange rate.
• Opening windows at night results in a reduction in the daytime indoor air temperature (e.g., at 2 p.m.) by 2.2–3.3 K for lightweight cellular concrete and 2.0–2.5 K for natural stone compared to the alternative without night-time ventilation.
• The use of high thermal capacity materials in partitions usually promotes a reduction in project costs and provides better structural capabilities (carrying higher loads).

Thermal comfort is a broad, multi-criteria issue that is difficult to analyse comprehensively. The authors are aware of the many limitations associated with the measurements presented. This study was an effort to simplify the assessment of microclimatic conditions in highly specific buildings like sports halls. When undertaking the study, the authors were under no illusion that they would be able to accurately determine the effect of point, directed solar radiation for every location and every moment. In addition, the building’s users did not have strictly assigned locations and visit times. Even in the case of a relatively stationary volleyball game, they were still moving around the hall. In addition, measurements were only made for certain specific metabolic and clothing insulation data. The sports hall can be the site of many different activities as a part of different sports disciplines. The authors focused on activities customarily carried out during the academic year with students and performed the analysis only for this specific-yet-broad user group. All of this makes the information on thermal comfort and that derived from measurements and from simulations indicative and should be treated as an average in terms of place and time.

The location of the device may also have had some small impact on the final results. However, it was the only possibility to perform measurements during the building’s routine operation. The location of the instrument was dictated by concern for its safety, as well as technical possibilities, based on the hall’s form of use. The sensors’ location could not interfere with the sports activities schedule.

It should be added that there are no clear, established guidelines on measuring thermal comfort in sports facilities in recognised standards and in the literature. In addition, there is a lack of consistency and clearly defined categories of sports, metabolic values and the corresponding thermal comfort temperature. It is therefore difficult to formulate general conclusions for this group of buildings, especially when they are built to be passive buildings, and for a specifically defined user group.

The authors are aware of the unavoidable approximations and simplifications that result from the manner, conditions and timing of measurements in the hall. Similar limitations also apply to simulation results concerning the average conditions in the hall’s centre. Nevertheless, the results obtained in this way should, in the authors’ opinion, allow meaningful comparisons of the analysed alternatives and aid in the search for correct directions for the design of such facilities.