Holistic analysis of indoor environmental quality in refurbished school using HAIEQ methodology - Czech case study

. The subject of this paper is a detailed analysis and evaluation - audit of the quality of the indoor environment in the reference zone of a primary school building in the Czech Republic. The analysis and subsequent evaluation is performed by the certified CTU HAIEQ (Holistic Assesment of Indoor Environmental Quality) methodology, developed at the Department of Building and Construction Engineering of the Czech Technical University in Prague. The analysis is based on a detailed survey of the building, measured data of physical variables of the indoor environment and subjective assessment from the user's point of view. The evaluation of the quality of the environment is carried out in 8 categories - LS Location and location of the building in terms of external environment and social connections; STI Structural-technical design and interior of the evaluated zone; TCW Thermal comfort in cold season; TCS Thermal comfort in warm season; IAQ Air quality; LC Light environment; AC Acoustic environment and EC Electro-magnetic, -ionic -static fields. Each category has 5-8 criteria to be evaluated. The outcome of the indoor environment audit using the HAIEQ methodology is the identification of critical areas and the proposal of possible measures to improve the current situation. The implementation of the proposed measures must be carried out in accordance with applicable regulations and laws by authorized persons. The method used does not guarantee that all problem areas will be found using it and the preparer is not responsible for problems not found during the analysis of the building. The results of the measurement and evaluation methodology are not a substitute for an assessment by a sanitary service.


Description of the object
It is a primary school building (1st to 9th grade), which has undergone reconstruction according to the project from 2020 (Fig.1). In the 1st floor of the primary school building there are cloakrooms and technical facilities of the school, in the 1st to 3rd floor there are classrooms and teachers' offices. In the 4th floor or attic there are 4 residential units and a school kitchen. Structurally, it is a brick building based on foundation strips. The load-bearing and non-load-bearing structures are made of bricks. The perimeter structures are made of solid burnt bricks. The existing vertical perimeter structures have been insulated with an external contact composite insulation system (ETICS) made of 180 mm thick facade mineral thermal insulation (λ = 0.039 W/m -1 K -1 ). The interior plaster is stucco. The external plaster is lime-cement. The ceiling of the 1st floor is vaulted brick into steel profiles, the ceilings of the higher floors are wooden. The roof truss was also insulated (with mineral thermal insulation of 340 mm thickness). The floors in the classrooms are made of OSB boards and vinyl. The windows are new plastic, glazed with insulating glass, Uw ≤ 0.95 W/m -². K -1 . The windows are fitted with all-round fittings with four-position handle and stop and centre seals. The windows on the south and east facades are fitted with front window blinds, the windows on the west facade with internal blinds. The heat source for heating and hot water for the primary school is two Junkers gas boilers located in the 1st floor of the dwelling units each have their own gas boiler and are not subject to assessment. The heating system is a two-pipe system, vertical and horizontal ducts are run loose (uninsulated) or in the wall in the classrooms, the heating elements in the classrooms are cast iron sectional, in PP1 steel plate. Heating elements in classrooms are fitted with thermostatic heads. The control is equithermal. Hot water is heated centrally in an indirectly heated tank located in the 1st floor in the gas boiler room. In all classrooms there is an additional Fig. 1 The building of the school under assessment E3S Web of Conferences 396, 01104 (2023) https://doi.org/10.1051/e3sconf/202339601104 IAQVEC2023 system of equal-pressure controlled ventilation in two versions. The ventilation units are either located in the classrooms or suspended from the ceiling of the classrooms. The units are connected to the exterior through the façade, the air supply to the classrooms is through fabric outlets, and the air exhaust is through grilles. 650/650 m 3 /h are supplied to/from the classrooms. CO2 sensors are installed in the classrooms. The operation of the classroom air handling units is controlled via a web application. Hygiene facilities are ventilated by windows and negative pressure fans, 1 st floor is ventilated by negative pressure mechanical ventilation.

Processing of information on the operation of the evaluated object
For the evaluated classrooms of the elementary school building, information from short-and medium-term orientation measurements of selected physical variables was processed. .The questionnaire survey was not conducted due to the lack of time of the users of the evaluated building. The measurements presented below are indicative and do not cover the entire operating cycle. The aim of the measurements is to provide an indicative indication of the status during the selected evaluation period.

Medium-term measurement of temperature and relative humidity, CO2 concentration and sound pressure level.
Medium-term orientation measurements of air temperature, relative humidity and CO2 concentration with the Netatmo system with a time step of 5 minutes were carried out from 19 May to 12 June 2022 in selected rooms. For the analysis and evaluation of the temperature, humidity and CO2 concentration data, the VISIEQ method from the certified CTU HAIEQ methodology was used, which allows an integrated view of the measured data and the temporal identification of problem situations. The VISIEQ graphs (Fig. 2, Fig.3, Fig.4.) show averaged values over the monitored period to indicate a recurring pattern (e.g. overheating in the morning); detailed waveforms of the measured values are stored in the archive of the processor. For the purpose of this assessment, temperature and humidity data were classified into 8 categories, and in the case of CO2 into four categories. The limits of the categories were set based on EN16798-1, Decree 268/2009 and the above mentioned methodology (see Table 1 to Table 3), so that category "I" corresponds to optimal values and category "IV" to values that are unsatisfactory. the entire building and hence the children had an alternative programme outside the school building. This situation was reflected in the measured values. The HVAC units were not operating at the time of the local investigation. The average PM10 concentration for the surveyed part of the building on 18 May 2022 was: 65.5.7 μg/m 3 (maximum 85.6 μg/m 3 in the computer room, minimum 42.9 μg/m 3 in classroom 7); for PM2.5 the average concentration was 5.36 μg/m 3 (maximum 6.38 μg/m 3 in the computer room and minimum 4.02 μg/m 3 measured in classroom 7). The average concentration of PM10 for the monitored part of the building on 13 June 2022 was: 7.84 μg/m 3 (maximum 14.27 μg/m 3 in the computer room, minimum 3.25 μg/m3 in classroom 10); for PM2.5 the average concentration was 1.32 μg/m 3 (maximum 1.63 μg/m 3 in classroom 7 and minimum 0.88 μg/m 3 measured in the computer room). The limit concentration of dust according to Decree 6/2003 Coll. for PM10 is 150 μg/m 3 ; for PM2.5 80 μg/m 3 . Another indicative measurement monitored the concentration of formaldehyde. The EXTECH VOC + CH2O Meter VFM200 was used for the measurement. Similar to the concentration of dust particles, formaldehyde was monitored in the three classrooms monitored (classroom 7, computer room, classroom 10), where the concentration was read three times over 15 minutes on both days of the site investigation. According to Government Regulation 361/2007 Coll., the permissible exposure limit for formaldehyde in the working environment is 0.4 ppm. The World Health Organization (WHO) recommends a mean 30-minute formaldehyde concentration of 100 μg/m 3 (0.08 ppm). This value should be safe, even considering the longterm effects of formaldehyde, including carcinogenic effects. In the Czech Republic, Decree No. 6/2003 Coll. (laying down hygienic limits for chemical, physical and biological indicators for the indoor environment of living rooms of certain buildings, including buildings for education and training) specifies an hourly limit concentration for formaldehyde of 60 μg/m 3 (0.048 ppm). The average concentration of formaldehyde throughout the building was 0.09 ppm on both days of the site investigation. The computer lab and classroom 10 had higher formaldehyde concentrations than classroom 7. In classroom 7, the formaldehyde concentration was more than double on the second day of the local investigation compared to the first day. Probably because the ventilation system was not operating at all on this day. The higher concentration of formaldehyde may be due to the presence of its source, e.g. in the form of OSB (oriented strand board) flooring. In both cases of the on-site investigation, the measurements were taken at a time when the ventilation system was not running, so it can be assumed that the real concentration would be lower during standard operating hours.

One-time lighting measurement
The light environment was measured with a UPRtek MK350S PREMIUM and an orientation measurement with a Testo luxmeter. In classroom 7, the artificial lighting was measured at the workplaces or benches. The measurements were taken after about 20 minutes from the start of the lighting system and with the blinds closed. Although three tubes in the luminaires were defective and did not work, it can be concluded that the level of illumination in the monitored area at all workplaces meets the requirements of EN 12464-1. The illuminance averaged over 800 lx, which is 300 lx more than the standard requirement, so the operation of this system is not entirely energy efficient. Higher illuminance values also increase the risk of glare. Given the layout and considering that two of the three classrooms surveyed have window openings in two side walls, it can be assumed that the classrooms have sufficient daylight during normal operating hours. The light spectrum of the light sources in classroom 7 corresponds to artificial fluorescent lighting. The alternate chromaticity temperature (colour of light) was measured to be 2930 K on average, which corresponds to a warm white colour. This is not suitable for the environment, especially if the system is to be used in combination with daylight during daylight hours.  Fig. 6, the data of the electromagnetic field intensity for individual frequencies including the sum value (green curve of the highest values in the graphs -TOTAL V/m) are processed. Table 6 gives an overview of the measured and plotted electromagnetic field frequencies. The values measured in all rooms are very low for all measured frequencies and the total value compared to the current permissible limits (Government Regulation No. 291/2015 Coll. on the protection of health against non-ionising radiation). The measured values also meet the health-precautionary limits according to the precautionary principle, i.e. E = 0.6 V/m (e.g. the so-called Salzburg limit).

Assessment of the quality of the environment
On the basis of the submitted documents, a survey of the buildings, measurements and a questionnaire survey, an evaluation of the quality of the environment in terms of 8 criteria is prepared, including the main areas reflecting the quality of the indoor environment in terms of meeting standard or other legal requirements and the response of users. Each of the criteria has several subcriteria allowing a targeted analysis of the quality of the environment. The following table shows the criteria that were assessed for the part of the building under evaluation:  Comments -the solution has the potential to be improved, but the situation does not require immediate implementation of the remedy 3 Serious deficiency -non-compliance with legislation, state of disrepair, non-functionality of equipment -it is recommended to correct the situation as soon as possible. -Change the control of the external blinds -one press to set in motion, one press to stop. -In south and east facing classrooms, ensure proper use of shading devices and ventilation to ensure maximum indoor comfort.
-When higher outdoor temperatures are expected during the day, it is advisable to use ventilation to pre-cool the rooms. -Install local under-ceiling fans in classrooms. In the event of higher temperatures, they will provide increased cooling of the occupants, mix the air in the room when the air feels stuffy, and disrupt the layers of stagnant air formed by the human body at low air velocities The ability of the ventilation system to adapt its mode of operation in response to the needs of the users, with due regard to user-friendliness, maintaining a healthy indoor environment 2

IAQ3
Ability of the ventilation system to report to the user on energy use 2

IAQ4
The ability of the ventilation system to report to the user on the quality of the environment in terms of air quality 2 IAQ5 Summary of air quality assessment results from measurement/simulation (if conducted) 1

IAQ6
Summary of air quality assessment results from the questionnaire survey (if conducted) N IAQ IAQ criterion assessment 1.8 Comment, recommendation: IAQ1 The current operation of the HVAC units does not fully exploit the potential for providing air quality in classrooms. Maintenance of the HVAC equipment has not yet been carried out, although the condition of the filters is already poor. IAQ2 There are CO sensors in the classrooms2 , but it is not clear from the application how and if they are used to control the HVAC units, or if the output/flows of the HVAC units are modulated or not. Users do not understand the data in the application and therefore do not use it practically to change user settings or to check the set operating status of the HVAC units. It is also confusing to set the desired temperature, while the HVAC units do not allow air heating. IAQ3 Informative Commentary. Modern metering and control systems should inform the user of the actual energy consumption (heat and electricity) that is within his/her control, depending on the user parameter settings (e.g. the performance of the air handling unit). IAQ4 -Users do not have clear and understandable information about the operation of the ventilation system and the air quality in the room.
-Organise an HVAC equipment manager or operator to ensure proper operation and maintenance settings.
-Check that the periodic inspection of the equipment is carried out according to the manufacturer's instructions and maintenance plan (weekly, 3monthly, semi-annually and annually, documented by a protocol) -Install an independent wall-mounted CO2, temperature and relative humidity indicator in the classrooms. Providing users with information on indoor air quality allows for a layman's control of the environment and alerts them to outliers.
-Modification of the application for HVAC control -Changing filters : In classroom 7, the lighting system (despite 3 defective sources) will provide illuminance higher than 800 lx, it is energy inefficient, 500 lx would be enough. The chromaticity temperature of the sources is too low. Defective sources have been found in other classrooms as well. LC2: The system does not allow changing the illuminance or changing the chromaticity temperature of the light (biodynamic lighting). LC3: Informative comment. Modern metering and control systems should inform the user of the actual energy consumption (heat and electricity) that is within their control, depending on the user's parameter settings (e.g. artificial lighting). LC4: In the case of mixed lighting, information on the current light quality can help prevent or address fatigue in the workplace. LC5: Unsuitable chromaticity temperature of artificial light. Too high illuminance on the working planeenergy inefficient, higher risk of glare.
recalculate the existing lighting system and modify it to ensure an illuminance value of 500lx and not more (e.g. use lower wattage fluorescent lamps) maintenance -repair malfunctioning power supplies, clean luminaires light sources with a chromaticity temperature in the neutral category, i.e. 3300-5300 K, would be more suitable.
-When reconstructing, consider installing dimmable sources or biodynamic lighting Installing acoustically absorbent materials will improve the acoustic microclimate in the room. The reverberation time and sound pressure level will be reduced, the clarity of the interpretation will be increased and the stress on the body from noise pollution will be reduced.

Summary of the environmental assessment and final recommendations
The assessed building has the potential to improve the condition of the indoor environment and thus increase the comfort of teachers and pupils. On the basis of the provided documentation, own survey and measurement of selected environmental parameters, a multi-criteria analysis and evaluation of the sub-components of the indoor environment and their mutual interactions was carried out. In all evaluated criteria the rating was 1 or 2, i.e. no comments or with a slight comment expressing the possibility of improvement. In none of the criteria assessed was there a rating of 3, expressing a serious problem requiring immediate correction. The greatest potential for improvement of the assessment area is in the criteria LC (Light Environment), AC (Acoustic Environment) and IAQ (Air Quality). Smaller but still significant potential for improvement is in the criteria TCW and TCS (Thermal comfort in warm and cold seasons of the year), LS (Location and siting of the building in terms of external environment and social connections) and STI (Structural and technical design and interior). No measures are proposed in criterion EC a.

Summary of recommended measures
A. Organisational measures -Education for teachers and management on energy performance of buildings and environmental quality -Monitor the energy consumption of the building on an ongoing basis, checking for anomalies at least at monthly intervals -the activity of the building's energy engineer.
-In south and east facing classrooms, ensure proper use of shading devices and ventilation to ensure maximum indoor comfort.
-With the expectation of higher outdoor temperatures during the day, it is advisable to use night ventilation to pre-cool the rooms.
-Organization of the HVAC equipment manager (operator) to ensure proper operation settings and periodic maintenance. It is possible to combine with the activities of the energy engineer and to deal with an external employee. Check that the periodic inspection of the HVAC equipment is carried out according to the manufacturer's instructions and the maintenance plan (weekly, 3-monthly, semi-annually and annually, documented by a protocol).
B. Maintenance modifications during normal operation -clean/replace HVAC filters -Change the control of the external blinds -one press to set in motion, one press to stop. The current method of operation results in the external blinds not being fully utilised.
-Checking the settings of the thermostatic heads and replacing them, if necessary, with a type suitable for the classroom (so that pupils cannot tamper with them). -In cooperation with the manufacturer, modification of the HVAC control application.
-Recalculate the existing lighting system and adjust it to ensure the illuminance value of 500lx and not more (e.g. use fluorescent lamps of lower power).
-Maintenance -repair malfunctioning light sources, clean luminaires, use light sources with chromaticity temperature in the neutral category, i.e. 3300-5300 K.
-Install an independent wall-mounted CO2, temperature and relative humidity indicator in the classrooms. Providing users with information on indoor air quality allows for a layman's control of the HVAC equipment's function and alerts them to outliers.
C. Building modifications, total system change -Installing acoustically absorbent materials in classrooms will improve the acoustic microclimate in the room. It will reduce the reverberation time and sound pressure level, increase the clarity of the interpretation and reduce the stress of the organism from noise pollution.
-When reconstructing the lighting, consider installing dimmable sources or biodynamic lighting.
-Floors made of OSB boards to be coated with a suitable coating or to change the floor layer -Install local ceiling fans in classrooms. In the case of higher temperatures, the airflow will provide increased cooling of the occupants, mix the air in the room when the air feels stuffy, and disrupt the layers of stagnant air formed by the human body at low air velocities.