Indoor air quality in educational institutions has long been an important and much-discussed topic among experts. During the pandemic years, the general public and politicians have also become aware of it in connection with its influence on infection prevention and health promotion. Learning needs fresh air.

Text Brigitte Rabl

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Influence of indoor air

Indoor air quality is undisputedly a key factor influencing our well-being. In educational institutions, studies (e.g. [1, 2, 3, 4]) have shown that it even improves teaching and learning success due to its influence on the ability to concentrate.

During the Covid-19 pandemic, indoor air has become the focus of attention in connection with airborne infection pathways and will continue to require further attention in the future with regard to infection protection and health promotion. The quality of indoor air is largely determined by its CO2 content, temperature and humidity. CO2 is considered an important indicator as it is easier to measure than other volatile substances that are released into the air by people and objects. The maximum permissible CO2 content is therefore a decisive parameter for indoor air quality. Educational facilities pose a particular challenge in this context, as the CO2 levels in rooms with high occupancy rates increase rapidly within a very short space of time. Experts and the Austrian Institute for School and Sports Facility Construction (ÖISS) have been dealing with this problem for many years and it is becoming increasingly urgent as the building envelope becomes more airtight.

_CO2 and fresh air supply

According to OIB Guidelines 3, 2023 edition [5], occupied rooms must be “sufficiently ventilated”. This requirement is specified with concrete numerical values in the “Guideline for the assessment of indoor air” [6] of the Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK) and in the ÖISS guidelines for educational buildings [7]. Over a defined assessment period, an arithmetic mean of the instantaneous values of < 1000 ^ppm2 is to be aimed for with regard to CO2 concentration in “indoor spaces for the permanent occupation of persons in which mental activities are carried out or which are used for ^{regeneration1} “. In addition to all classrooms, these rooms also include workrooms for teachers, administrative areas, open learning zones, libraries, multi-purpose rooms, etc. An arithmetic mean value of < 1400 ppm is used as a general guideline value for indoor spaces where people are permanently present. Education-specific examples of this are leisure rooms / home bases, common rooms for teachers and staff, rooms for sport and exercise, dining rooms, etc.

According to studies [8], if you want to ensure these values in fully occupied classrooms using only manual window ventilation, you would have to air the room for five minutes approximately every twenty minutes. Experience shows that such consistent ventilation behavior cannot be established in educational institutions. There are many reasons for this: a lack of awareness of the issue, disruption to lessons, issues relating to supervision, loss of comfort and energy in the cold season, noise emissions when windows are open, etc.

For this reason, experts agree that it is difficult to achieve appropriate and hygienically perfect indoor air quality in educational facilities without ventilation and air conditioning systems. In the “hot phase” of the pandemic, rapid action was required above all to reopen or keep educational facilities open. In no time at all, the market was flooded with an unmanageable range of products and technologies, all claiming to be the best. Only in the aftermath were research projects able to provide more clarity about their actual efficiency.

ÖISS guidelines for educational construction

In response to the pandemic, the indoor air-related specifications of the ÖISS guidelines for educational buildings were also comprehensively revised in the ÖISS working group “Schoolrooms “³ with the support of relevant experts and published in September 2023 in the new chapter “Sustainability, energy, indoor climate and building services”. The revision was carried out in consultation with the BMK’s Indoor Air Working Group and the ÖNORM H 6039 committee [9].

The new version of the guidelines contains information on the importance of indoor air, room concepts and the distribution of people, user behavior, ventilation concepts, infection protection, CO2 levels indoors, air humidity, the required outdoor air supply – including for sports halls – as well as the renovation and retrofitting of existing buildings. In addition, the various types of ventilation are presented with their advantages and disadvantages and the technical requirements for mechanical ventilation systems are defined, such as information on heat and moisture recovery, energy efficiency and maximum noise levels.

The guideline also takes a stance on room air purifiers, which are repeatedly brought to educational institutions and propagated, as they can be retrofitted quickly and relatively inexpensively. Although these systems can help to quickly reduce the aerosol particle concentration and thus the viral load in the room in acute infection situations, they are not very suitable for educational establishments as they work without a fresh air supply and therefore do not reduce the CO2 concentration. Further information on air purification devices can be found in a BMK position paper [10].

Comprehensive information on the subject of indoor air in educational institutions can also be found in the “Position paper on ventilation requirements in educational institutions” published by the BMK’s Indoor Air Working Group [11].

New standard in federal schools

In May 2023, the Federal Ministry of Education, Science and Research (BMBWF) made the decision to generally equip new federal schools (AHS, BMHS) with mechanical ventilation and air extraction systems. The technical requirements for these systems contained in the ÖISS guidelines [12] are binding for federal schools.

However, the BMBWF is not responsible for the construction and maintenance of compulsory schools (primary and secondary schools). These are predominantly the responsibility of the municipalities and are based on statutory regulations of the federal states. Private schools are also not subject to federal regulations in this respect.

Decisions here are still made on a project-specific basis, as with all renovation projects, where retrofitting depends on the structural, spatial and technical requirements (e.g. room height) as well as the economic conditions.

Ventilation concept

In any case, a ventilation concept is required for new buildings, extensions and conversions of educational facilities [6, 12], from which the type of ventilation strategy to be planned and implemented for the respective room use can be derived. Ventilation concepts can also include a combination of several interacting ventilation measures (e.g. mechanical ventilation systems and additional window ventilation during breaks).

Compliance with the required CO2 values should be verified using suitable simulation programs [13, 14], assuming a reasonable and realistic window ventilation frequency of at least 50 minutes.

Challenges

The use of ventilation and air conditioning systems has clear advantages in terms of indoor air quality and building-related infection prevention measures. At the same time, these systems place high demands on planning, design, operation and regular maintenance. Shortcomings in this regard lead to problems in the everyday life of educational institutions. In order to ensure user acceptance during operation, it is particularly important to comply with the limit values with regard to noise pollution and the avoidance of draughts. The current requirements for sound insulation and energy efficiency of ventilation systems also require shorter distances and larger flow cross-sections for air routing, which means that more system components are likely to be installed on the roofs of educational facilities. It should be noted that the utilization pressure on roof surfaces is increasing due to energy and climate-relevant measures (e.g. photovoltaic systems, green roofs) and, particularly in densely built-up areas, also for the use of open spaces. A holistic view and project-specific consideration are therefore required for all projects.

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¹ Regeneration refers to sleeping and rest rooms (e.g. in nurseries). Leisure-oriented rooms fall into the category < 1400 ppm.

² ppm = parts per million, number of parts per million parts

³ In addition to Consultants from ÖISS, the “School Space” working group includes official decision-makers such as the Federal Ministry of Education, Science and Research (BMBWF), education directorates and state representatives as well as the Bundesimmobiliengesellschaft (BIG). Relevant experts are also brought in on a temporary basis for the individual subject areas.

Literature and list of standards

[1] Slotsholm ApS: Socio-Economic Consequences of better air quality in primary schools. In collaboration with the Centre for Indoor Environment and Energy at the Technical University of Denmark and the Dream Group. Denmark, 2012.

[2] Wargocki, P.; Wyon, D.P.; Sundell, J.; et al.: The effects of outdoor air supply rate in an office onperceived air quality, Sick Building Syndrome (SBS) symptoms and productivity. Indoor Air 10: 222 – 236, 2000.

[3] Shaughnessy, R.; Haverinen-Shaughnessy, U.; Nevalainen, A.; et al.: A preliminary study on the association between ventilation rates in classrooms and student performance. Indoor Air 16: 465 – 468, 2006.

[4] Allen, J.; MacNaughton, P.; Satish, U.; et al.: Associations of cognitive function scores with carbon dioxide, ventilation, and Volatile Organic Compound Exposures in office workers: a controlled exposure study of green and conventional office environments. Environ Health Perspect 124: 805 – 812, 2016.

[5] Austrian Institute of Construction Engineering (OIB): OIB Guidelines 3: Hygiene, Health and Environmental Protection, 2023.

[6] Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK): Guideline for the assessment of indoor air – carbon dioxide as a ventilation parameter, 2023.

[7] Austrian Institute for School and Sports Facility Construction (ÖISS): ÖISS Guidelines for Educational Construction, Chapters 7 & 8 – Sustainability, Energy, Indoor Climate and Building Services, 2023.

[8] University of Stuttgart, IGTE: Final report of the pilot project “Experimental investigation into the risk of infection in classrooms in Stuttgart schools”, 2021.

[9] OENORM H 6039: Ventilation systems – Controlled mechanical ventilation of school rooms, classrooms, group rooms and rooms with a similar purpose – Requirements, dimensioning, design, operation and maintenance, February 1, 2023.

[10] Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK): Position paper on ventilation-supporting measures for infection prophylaxis – use of air purifiers and introduction of active substances into indoor air, 2022.

[11] Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK), Indoor Air Working Group: Position paper on ventilation requirements in educational institutions, 2023.

[12] Austrian Institute for School and Sports Facility Construction (ÖISS): ÖISS guidelines for educational construction, September 2023.

[13] Rojas, G.; Greml, A.; Pfluger, R.; Tappler P.: Assessing the “sufficient ventilation” requirement for Austrian buildings: development of a Monte Carlo based spreadsheet calculation to estimate airing intervals and mold risk in window ventilated buildings. International Journal of Ventilation, 1 – 10. doi.org/10.1080/14733315.2023.2198788, 2023.

[14] Ventilation calculator CO -SIM, available at raumluft.org, checked on February 12, 2024.