Costs–benefit analyses are a typical (but not the only) approach to radon testing and remediation decisions. This would provide the basis for a subsidy programme to create (monetary) incentives and have an effect. Maintaining or increasing the value of one's own property through radon remediation (possibly with a certificate) could be a convincing motivation for action that does not directly address health protection. However, not all residential building owners follow the cost–benefit logic. Some of them value the health risk or their own health so highly that they do not consider a cost–benefit analysis to be appropriate nor do they consider a subsidy program to be an incentive to radon remediation (or to radon testing beforehand).

To efficiently and effectively address the target group, it seems advantageous to focus on residential building owners who are planning remediation work anyway and are located in radon precautionary areas. These may be people who have applied for subsidies for energy-efficient remediations or remediations to improve burglar-proofing or to convert to age-appropriate bathrooms. Information material and free radon tests can be offered here. Another approach would be to conduct numerous free radon tests in radon precautionary areas – as well as outside these areas. An information and measurement campaign on the topic of radon could also specifically point out the advantages of energetic remediations and related subsidy programmes – and thus provide additional motivation for building remediation (against the background of the realisation that building remediations typically take place for several reasons).

A subsidy programme for radon remediation can have a significant "push" on building owners who already have a certain openness towards radon measurement or radon remediation or who are not sure about radon remediation. In contrast, a subsidy programme rarely seems to cause a change of opinion or intention to act among people who tend not to consider radon measurement.

An "optimal" subsidy rate is not a sufficient condition for the extensive usage and high effectiveness of the subsidy programme. A strong influence on the success of the subsidy programme is rather the embedding of the subsidy programme in a long-term or continuous information campaign with sufficient funding. The effect of the subsidy programme can be multiplied with subsidised (or free) radon measurements (at best measurement campaigns) as well as expert advice and support.

The aim of information campaigns would be to first carry out a radon measurement and, if necessary (i.e. if there is evidence of sufficiently high radon contamination), provide the owners of residential buildings with an informed cost–benefit analysis. The entire population (and not only the owners of residential buildings) is considered to be a useful target group in order to spread the topic among the generation population (and thus raise awareness of radon among the landlords via the tenants) and to encourage radon tests.

National and international experience suggests that at least a final testing of the effectiveness of radon remediation by a government body/authority (final radon test) is beneficial. However, the initial testing for radon contamination should be carried out by actors who are trusted by the owner-occupiers and landlords of apartment buildings. The actors should be seen as neutral, independent actors without their own economic interest in radon remediation. An example would be the authorised district chimney sweep (with the restriction that they come into play only when boilers or gas boilers are present), consumer protection institutions (consumer centres), or qualified independent (certified) advisors.

Experiences from other countries show that individual counselling (as a direct follow-up after the tests) of those cases with radon exposure suggesting remediation is a key success factor for an effective subsidy program. Consultations that cover the application for subsidy are conceivable.

Part of a subsidy programme for radon remediation could be state/official "informational support" throughout the entire process by means of central contact persons. A considerable increase in radon remediation (e.g. as a result of a subsidy programme) would bring about a high demand for advice and consequently an increase in the number of radon- and further training for consultants and remediation companies.

The lack of qualified advisors and remediation service providers would hinder the effectiveness of the subsidy programme. A seal of quality for radon experts and an easy-to-find list of experts for certified qualified/expert consultants and remediation companies are approaches to creating confidence among home-owners and actually achieving the expected health protection effects.

In the interviews, there were clear indications that a subsidy programme is interpreted by the target group as a kind of package of measures that goes beyond monetary incentives.

To be noted:

• The individual government measures meet the different individual needs of residential building owners (e.g. the need for more information, easier access to radon measurements, or financial support for radon remediation). The measures are thus (at least partly) directed at different parts of the target group. A broad range of different measures (as can also be found in government measures in the field of energy remediation) thus covers as large and diverse a share of the target group as possible.
• The measures are partly interlinked in a reinforcing manner (e.g. by referring the subsidy programme for radon remediation in the context of a consultation and providing support in the application phase).
• A subsidy programme for radon remediation not only offers monetary incentives for remediation but can also have a "signalling effect" on residential building owners and tenants with respect to the relevance of radon exposure in residential buildings – and thus (if actively communicated) represent a potentially effective trigger for radon measurements. This in turn would lead to an increase in radon remediation.