Radon protection thanks to ventilation
RadonVent research project: decentralised ventilation reduces radon activity concentrations in indoor spaces
What is radon?
The chemical element radon-222 is a radioactive noble gas and occurs naturally in Germany in varying concentrations in the soil. The gas is invisible and cannot be detected by humans through smell or taste. It enters the air and living spaces unnoticed through leaks in the building envelope that are in contact with the ground and can contaminate the indoor air. Long-term inhalation of high radon concentrations can have health consequences and lead to lung cancer, for example.
Why is radon so dangerous?
The radioactive noble gas radon-222 is produced in the soil and enters buildings via the soil air, where it can accumulate in the indoor air. It is invisible and odorless, but the radioactive decay products can be deposited in the lungs through breathing. These emit ionizing radiation, which increases the long-term risk of lung cancer.
The Federal Office for Radiation Protection has set a reference value of 300 Bq/m³ for the annual average concentration of radon-222 activity in indoor air in Germany. If this value is exceeded, appropriate protective measures are necessary—such as sealing, ventilation systems, or structural measures as part of renovation or new construction. This allows the radon concentration in the air to be permanently reduced and effective radiation protection for humans to be achieved.
What radon protection measures are available?
In accordance with the Radiation Protection Act, regulations for the first time came into force in 2020 to protect against radon in buildings with common rooms, such as apartments, daycare centers, and schools, as well as in workplaces. These are supplemented by additional requirements if the building is located in a designated radon prevention area.
The protective measures provided for in the Act and the Ordinance include, in particular:
- Sealing measures on components in contact with the ground (e.g., floor slabs, joints, pipe penetrations)
- Reduction of radon-222 activity concentration under the building
- Limitation of cracking in walls and floors in contact with the ground
- Extraction of radon at edge joints or under seals
- Changing the pressure conditions in the building to reduce the penetration of radon from the soil air
These measures help to improve radiation protection and significantly reduce the health risk to residents and employees. In addition, the DIN/TS 18117 series of standards describes structural and ventilation measures for radon protection. It specifies the requirements of the law and regulations and also highlights the additional possibilities offered by ventilation technology for effective radon protection.
What are the obligations regarding radon protection in Germany?
According to the Radiation Protection Act (StrlSchG), all federal states were required by the Federal Ministry for the Environment, Climate Protection, Nature Conservation, and Nuclear Safety to designate areas in which buildings are expected to frequently exceed the reference value for radon concentration by December 31, 2020. This reference value applies nationwide and is 300 Bq/m3 for the annual average in residential buildings, schools, and workplaces. High concentrations of radon-222 activity occur, for example, in the German low mountain ranges and former mining areas in the federal states of Saxony, Thuringia, Bavaria, and Baden-Württemberg. To protect residents, targeted reduction measures must be implemented in these areas. Schools and employers are also obliged to check compliance with the reference value by taking measurements and, if necessary, implementing protective measures.
How high is the radon concentration in my home?
You can find out whether your place of residence is located in an area with elevated radon levels on the interactive radon map from the Federal Office for Radiation Protection, which shows the estimated average radon-222 activity concentration in residential areas for each municipality.
Reduce radon activity concentration through ventilation
The simplest measure for reducing radon-222 is ventilation. However, continuous ventilation via open windows has the disadvantage of causing rooms to cool down uncomfortably. Constant reheating is not only inefficient, but also expensive. Especially in existing buildings or in the case of renovation, decentralized residential ventilation with heat recovery is therefore a simple and efficient measure to enable continuous air exchange in order to reduce the concentration of radon-222 activity.
"RadonVent" research projectHow ventilation systems can reduce indoor radon levels
The “RadonVent” research project investigated how dangerous indoor radon concentrations can be effectively reduced through the use of modern ventilation systems. The aim of the project was to develop a technically mature and practical solution that would enable homeowners and apartment owners to permanently protect their buildings from radon without costly renovations or energy losses.
- UFZ Department of Environmental Informatics headed by Prof. Dr. Holger Weiß
- Bergsicherung Schneeberg GmbH & Co. KG
- Building and Apartment Management GmbH Schlema
- SARAD GmbH
- Dr. Jörg Dehnert from the Saxon State Office for Environment, Agriculture, and Geology (LfULG)
Research project "RadonVent": Many thanks to our partners!
Radon residential ventilation: Decentralized ventilation to reduce radon activity concentration
Together with its research partners, the team at inVENTer GmbH conducted extensive field tests in a region with elevated radon levels. The tests examined how decentralized ventilation systems with intelligent sensor control can reduce radon activity in indoor air.
The results clearly show that the use of such systems can significantly reduce radon exposure and thus contribute to a healthier indoor climate.
The core element of the research is the combination of precise sensor technology, automatic control of air exchange, and additional sealing of the building envelope. This forms the basis for an intelligent radon ventilation system that can be easily retrofitted in the future and can make an important contribution to health protection in living and working spaces, both in new and existing buildings.
Good to know!
The effectiveness of decentralized ventilation systems in reducing radon-222 activity concentrations has also been investigated in a scientific study by the Helmholtz Centre for Environmental Research (UFZ), among others. The findings of Altendorf, Grünewald, and other researchers (2022) show that targeted ventilation can reduce radon exposure in living spaces by up to 80%.
In addition,...
supplementary studies show that the effect of decentralized ventilation systems for radon reduction can also be realistically modeled and optimized using modern flow simulations (CFD). Further information on this can be found in this study:
How can radon be measured?: Measuring radon levels with ventilation systems from inVENTer
In order to verify the effectiveness of decentralized ventilation systems in reducing radon, researchers from inVENTer carried out extensive measurements in radon-contaminated buildings as part of the “RadonVent” project. An uninhabited test apartment in a region with high radon-222 levels was selected for practical testing. There, continuous measurements were taken to determine how radon activity concentrations changed with and without active ventilation.
Initial preliminary tests already showed that the use of ventilation systems with heat recovery – such as the iV14-Zero – could significantly reduce the radon concentration in the indoor air. Overall, the measurement results confirmed that decentralized ventilation systems noticeably reduced radon levels.
The data obtained in the project was scientifically evaluated through further field tests, simulations, and calculations. The aim was to develop a fully tested and practical solution that is suitable for different building types and exposure situations. This technology proved to be particularly advantageous in existing buildings: it was relatively easy to retrofit and at the same time ensured a healthy supply of indoor air without any significant energy loss. The project thus made an important contribution to simple, safe, and intelligently controlled radon protection in living and working spaces.
ConclusionThe most important radon protection measures
The results clearly show that modern radon protection can now be implemented effectively and practically using sophisticated ventilation technology. A targeted ventilation system enables continuous air exchange and reliably reduces elevated radon concentrations. This provides sustainable protection against radon—regardless of user behavior and without unnecessary energy loss.
Performing radon measurements:
The basis for any protective measures is the measurement of radon concentrations indoors—ideally over a period of one year, or alternatively, for example, over three months during the heating season, in order to obtain reliable average values.
Install controlled ventilation:
A decentralized ventilation system with heat recovery ensures continuous air exchange and permanently reduces radon exposure — particularly effective in radon-prone areas.
Waterproofing floor slabs and basements:
In new buildings, radon-proof membranes or special sealing systems should be installed under the floor slab in affected areas.
Sealing leaks:
Cracks, joints, and penetrations in the basement and floor area should be carefully sealed to prevent radon from entering from the ground.
Regulate pressure conditions:
Ventilation or structural measures can be used to create a slight overpressure in the building, which reduces the penetration of radon.
Long-term monitoring:
Once measures have been taken, regular monitoring of radon levels is recommended to ensure long-term success.
Frequently asked questions about radon and ventilation
What is radon and why is it dangerous?
Radon is a radioactive noble gas that can penetrate buildings from the ground. It is colorless and odorless and can cause lung cancer if exposure is prolonged. Radon can accumulate particularly in ground floor and basement rooms.
How can I determine whether my house is affected by radon?
The safest way is to measure radon levels. There are measuring devices or test kits available for this purpose, which are used over several weeks or months. In Germany, there are also designated radon prevention areas where there is an increased risk.
At what level is radon considered dangerous?
The Radiation Protection Act sets a reference value of 300 Bq/m³. If this value is exceeded in the annual average, measures should be taken to reduce it.
How does a ventilation system help against radon?
A decentralized ventilation system ensures continuous air exchange and prevents radon from accumulating indoors. Modern systems with heat recovery keep the heat inside the house – providing both radon protection and energy efficiency.
What is the RadonVent research project investigating?
The RadonVent project is researching how intelligent, sensor-controlled ventilation systems can automatically detect radon and reduce it through targeted air exchange. The aim is to develop a practical, comprehensive solution for new and existing buildings.
Do I need to renovate my house to retrofit a ventilation system?
No. Decentralized ventilation systems can usually be installed without major alterations to the building structure. This makes them particularly attractive for retrofitting in existing buildings.
How long does a radon measurement take and when should it be carried out?
A reliable measurement should be taken over a period of one year, or alternatively over three months of the heating season. This allows meaningful average values to be determined.
What other radon protection measures are advisable?
In addition to ventilation, sealing cracks and joints, radon-proof floor slabs, and regular monitoring of radon levels also help to keep exposure permanently low.
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