Review of Ventilation regulations in the Nordic countries: Towards Harmonization

The Nordic Ventilation Group (NVG) has compiled information related to regulations for ventilation and indoor air quality as set by the authorities in the Nordic countries. At present, the regulations are quite diverse across these countries, and the intention of the NVG effort is to provide a basis for future harmonization.

Keywords: Requirements, guidelines, standards, ventilation, indoor air quality, airflow rate

Background

There is a wide variety of different regulations and guidelines concerning indoor air quality and ventilation in the Nordic countries. Some are binding, some are general guidance. There are legislative regulations issued by various authorities, and there are guidelines issued by industry actors; all these have the potential to influence how ventilation is designed, commissioned, and operated.

A document prepared by the Nordic Ventilation Group [NVG, 2025a] shows that the guidance in the different Nordic countries is often structured differently. Typically, there are different authorities responsible for aspects related to the design of buildings, and to public and occupational safety and health, respectively. Within the same country, different authorities may provide diverging guidance.

This article illustrates the similarities and diversities of ventilation regulations across the Nordic countries. The intention is that this compilation, together with other efforts by NVG, shall contribute to future harmonization of the area.

The referenced NVG document has been prepared by Lars Ekberg with major contributions especially from Alireza Afshari, Guanguy Cao, Risto Kosonen, Jarek Kurnitski, Siru Lönnqvist, Arsen Melikov, Bjarne W. Olesen, Pertti Pasanen, Sasan Sadrizadeh, and Peter G. Schild.

Ventilation rates in residential buildings

The regulations of all considered countries specify minimum requirements on outdoor airflow rates normalized per m² floor area. The values range between 0.30 l/s per m² and 0.5 l/s per m². The lowest and highest values are found in Denmark and Estonia, respectively. The Danish regulation does not specify any required ventilation rate per person. In the other countries, the requirements range from 4 l/s per person in Sweden, 6 l/s per person in Finland, and 7 l/s per person in Estonia and Norway (the Norwegian value is specified for bedrooms as 26 m³/h per person, which is slightly more than 7 l/s per person. In all countries, the required ventilation rate shall be the highest of the floor area-specific and the person number-specific value.

A distinguishing feature of the Finnish regulation for new residential buildings is that dwellings shall have a total ventilation rate of at least 18 l/s, to prevent too low airflow rates in small apartments (based on the 0.35 l/s per m² requirement). Another feature for new Finnish residential buildings is that it should be possible to increase the air flow rates up to +30 %, and also to reduce them, but not more than -60 % from the nominal design value.

As opposed to Finland and Sweden, the regulations in Denmark, Estonia, and Norway specify requirements and/or guidance regarding the minimum exhaust airflow rates in wet rooms (kitchens, bathrooms, and toilets). In Sweden, and Finland, similar values are applied in practice, despite the lack of authoritative guidance.

Figure 1 shows calculated examples for apartments of the various sizes indicated in Table 1. For small apartments, the Danish regulation leads to substantially higher airflow rates compared to the other countries. This is primarily due to the high required exhaust airflow rate in the kitchen. The high values for Norway and Sweden are also due to high exhaust airflow rates.

The calculations have been made under the assumption that when the air passes from supply terminals in bedrooms to exhaust terminals in wet rooms and the kitchen, it is also utilized to ventilate the living room as transfer air, which in some cases can influence the dimensioning air flow rate.

Table 1. Types of indoor environments considered in examples calculated for comparison.

Figure 1. Calculated examples of minimum required airflow rates (l/s per m² floor) applied to new apartments of different sizes, as described briefly in Table 1. The airflow rates have been determined solely with respect to indoor air quality, not comfort cooling. Details regarding the input data and the calculations are provided in NVG (2025a).

Ventilation rates in non-residential buildings

The regulation in Denmark uses a different approach than those in the other Nordic countries, since it prescribes specific airflow rates to a limited extent only. It is stipulated, for childcare and educational premises, during occupied hours, that the ventilation rate may not be below 0.35 l/s per m² floor area, and the CO₂ concentration in the room may not exceed 1000 ppm. No quantitative rules are given for non-residential indoor environments other than educational ones. Instead, there is a reference to Danish standard, which, in turn, refers to EN 16789-1.

The Estonian regulation is based on national annexes pertaining to the European norm EN 16798. These annexes have similar power compared to building codes. However, a new building code that will comprise ventilation and indoor climate is under development. For non-residential buildings, the national annex specifies airflow rate requirements that generally follow Category II values of EN 16798-1:2019. The requirements are specified for various typical rooms. For instance, in classrooms and meeting rooms the requirement is 8 l/s per person (4 l/s·m²), and in offices 10 l/s per person (1.5 l/s·m²).

The Finnish regulation requires at least 6 l/s per person. However, this value may be reduced in existing buildings to 4 l/s per person if it can be shown that this lower level does not pose a risk of sanitary nuisance. The airflow rate may not be below 0.35 l/s per m² floor area during times of occupancy.

Both the Norwegian and the Swedish regulations require at least 7 l/s per person (in Norway expressed as 26 m³/h per person). Furthermore, in both countries the regulations stipulate a baseline floor area specific airflow rate to which the person-specific value is added. In Norway, this value is 0.69 l/s per m², and in Sweden, 0.35 l/s per m².

Figure 2 shows calculated examples for the three different types of non-residential environments indicated in Table 1. The REHVA/NVG cases shown in Figure 2 refer to NVG (2025b), which, in turn, refers to EN 16798-1 and to REHVA (2018). The higher values for offices in Estonia and Norway, and from calculations for low polluting materials based on EN 16798-1 are due to higher floor area specific airflow rates in these cases.

Figure 2. Calculated examples of minimum required airflow rates (l/s per person) applied to non-residential settings of the different types briefly described in Table 1. The airflow rates have been determined solely with respect to indoor air quality, not comfort cooling. Details regarding the input data and the calculations are provided in NVG (2025a).

It is important to note that the calculations summarized in Figure 2 have been made in accordance with the minimum requirements set by the authorities. For example, in Finland, when designing non-residential buildings, the minimum requirements set by the authorities are rarely followed; instead, the calculations are typically based on the Indoor Climate Classification (Ahola et al., 2019).

Carbon dioxide as an indicator

Carbon dioxide concentration is used as an indicator of ventilation adequacy in all the countries considered. Denmark, Estonia, Norway, and Sweden use a guideline value of 1000 ppm in indoor air (all assuming that the outdoor concentration is 400 ppm). As indicated in the previous section, in Denmark, it is a requirement to use this value when dimensioning the ventilation in childcare and educational premises. In Norway, on the contrary, this value is used as guidance but not part of the regulation. In Estonia, exceptions are made for meeting rooms, cinemas, and theatres, where room concentrations up to 1200 ppm are accepted according to a national annex pertaining to the European norm EN 16798. However, according to the Estonian energy regulation, the 1000 ppm value shall be used as a setpoint for demand-controlled ventilation (DCV) in any building.

The approach in Finland is instead to specify an accepted increase of the concentration above that outdoors. In new buildings, the concentration should not exceed 800 ppm above that outdoors. In existing buildings, the corresponding accepted addition is 1150 ppm. In cases with an outdoor concentration of 400 ppm, these values correspond to 1200 ppm in new buildings and 1550 ppm in existing ones.

These values can be compared to the common proposal presented by NVG, REHVA, and EUROVENT association [NVG, 2025b]. The proposal suggests that the following CO₂ concentration setpoint values may be used as an alternative for control purposes. The values represent the added concentration above that outdoors.

·         +500 ppm in rooms where the floor area is >6 m² per person;

·         +600 ppm in classrooms;

·         +800 ppm in other rooms where the floor area is <3 m² per person.

For further comparison, we can note that the standard EN 16798-1 suggests three different CO₂ concentrations above outdoors (assuming a CO₂ emission of 20 l/h per person): For occupants with special needs with respect to indoor air quality, the guideline value is 550 ppm above outdoors. The “normal” value is stated to be 800 ppm above outdoors. The value of 1350 ppm above outdoors is valid for two less stringent indoor environmental categories. The standard states that these concentration levels are not associated with any health risk but may decrease comfort.

In summary, the guidance referenced above regarding maximum accepted CO₂ concentrations in indoor air ranges between 900 ppm and 1750 ppm, assuming 400 ppm outdoors. Clearly, this range is wide; the ventilation rate needs to be 2.7 times higher to meet the lower of the two concentration levels.

Discussion

The purpose of the present document is to gather important information related to the guidance and requirements for ventilation and indoor air quality as set by the authorities in the Nordic countries. The intention is for the document to serve as a basis for future harmonization of this field.

This compilation clearly shows that we do things differently in different countries, countries that fundamentally have very similar conditions regarding climate, building technology, etc. One difference worth mentioning is connected to ongoing EU harmonization work, and varying willingness to adopt available EU standards at a national level. For example, in Denmark, the building regulations refer to EU standards. In Norway, the regulations have been adapted to EU standards, and in Estonia, a national appendix to the applicable EU standard is used. In contrast, the Swedish authorities have avoided referring to these international guidelines in any concrete way. Notably, the new Swedish building code, coming into effect in July 2025, makes general function requirements, but it does not provide any advice, nor does it refer to any standards or other guidance.

The Nordic Ventilation Group works to spread knowledge about how we in the Nordic neighbouring countries work to ensure that buildings are properly ventilated and provided with fresh and healthy indoor air. The idea is that we can learn from each other, and there is much to gain from harmonizing regulations and methods. An important benefit expected from the harmonization would be that we can become better at managing the process, from requirement formulation through design and construction to operation and maintenance, without getting lost along the way.

References

Ahola, M., Säteri, J., and Sariola, L. (2019) Revised Finnish classification of indoor climate 2018, E3S Web of Conferences, 111, 02017, CLIMA 2019. https://www.e3s-conferences.org/articles/e3sconf/pdf/2019/37/e3sconf_clima2019_02017.pdf

EN 16798-1:2019. Energy performance of buildings – Ventilation for buildings – Part 1: Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics – Module M1-6. CEN.

NVG (2025a) Summary of Guidance and Requirements on Ventilation set by the Nordic Authorities. Document prepared by the Nordic Ventilation Group. http://www.scanvac.eu/nordic-ventilation-group-nvg.html

NVG (2025b) Model Indoor Environmental Quality regulation aligning with new provisions of the 2024 EPBD recast. Common proposal by Nordic Ventilation Group, REHVA and EUROVENT association. http://www.scanvac.eu/uploads/9/4/5/2/94521553/ieq_guidance_2025.pdf

REHVA (2018) REHVA Guidebook GB 25 Residential heat recovery ventilation, REHVA Federation of European Heating, Ventilation and Air Conditioning Associations.