There are various actions to be implemented to create new ones radon-resistant buildings e reduce exposure to radioactive gas in the case of existing buildings. Every design solution must be well studied and, in order not to be frustrated, it must also be well executed from a technical point of view. Useful suggestions can be found in the “National Radon Action Plan 2023-2032”, recently published, with which Italy has equipped itself with an action plan for the fight against radon with the aim of addressing the risks long-term exposure to radioactive gas in the workplace and at home.
The Plan contains, in fact, various indications to prevent and reduce the entry of radon in the case of new buildings and renovations. Appendices 2.1 and 2.2 are dedicated to intervention methodologies normally used in current practice for the remediation or prevention of radon pollution. Although most of the techniques can find generalized application, each intervention must be assessed according to the specific case. For example, there may be architectural constraints that limit the possibilities for action.
When there is a risk of radon pollution there are however conditions to pay attention to. The plan details the main ones.
1 | Separation
To implement a radon protection strategy, a first action consists of separate the environments in which you live and work from the basements and cellars. Radon tends to concentrate in cellars and closed semi-underground spaces and, in general, in environments in contact with the ground. This is an aspect that may not be easily manageable in the case of renovations.
Another pitfall can be represented by vertically developed rooms, such as stairwells and elevators if directly communicating with the rooms in contact with the ground, such as cellars. In this case, elevators and stairs could bring radon to the upper floors due to the chimney effect. Insulating doors and access to underground rooms only from the outside could be easy to implement solutions. Obviously, to avoid costly interventions on the existing structure, both in-depth knowledge of the existing structure and the carrying out of a test campaign, commensurate with the size of the work, which involves measuring in points of the building chosen ad hoc, are recommended.
2 | Isolation
Creating completely watertight basement floors to separate them from the upper ones is not possible, but the construction elements, waterproofing sheaths and insulating layers can be used to create seffective radon prevention systems.
3 | Duct ventilation
The pipes serving the building if they pass through the building starting from the foundation level they can be a potential point of entry and diffusion of radon. A solution identified by the annex to the National Action Plan consists in providing for the passage of the systems through the perimeter walls, also creating a filling, perhaps in gravel, which allows adequate ventilation in order to avoid radon concentrations.
4 | Make use of the crawl space
The natural ventilation it can constitute a barrier to the spread of radon towards interiors. This can be done by exploiting crawl spaces. These can be connected with the lateral fillings at underground level created to remove the water present in the ground, to facilitate the transit of air in the subsoil and to prevent it from becoming enriched with radon.
5 | Plan interventions
Plan the project interventions in order to develop a good strategy in the construction phase, i.e. when the geotechnical information on the foundation site is known, is a good practice to implement in the case of new buildings. As underlined in the document, in fact, often only after the start of the works and after the necessary investigations have been carried out, data on the permeability of the soil is available, which will influence the choice of measures to be adopted to reduce the risk of radon pollution. And then – as we said – planning is fundamental, it is a matter of foreseeing a coordinated series of interventions to be carried out, in the construction phase, based on the critical issues that may emerge.
«In principle – it is recommended in the Plan -, intervention techniques at the ground-building contact level are to be favored, such as for example active or passive depressurization of the crawl space or creation of the so-called radon-well in the case of foundation foundations: moreover, these are commonly used solutions and are not of particular technical complexity”. As for the sealing solution, this «although systematically pursued, alone is certainly less effective and is generally complementary to other main interventions».
6 | Reinforced concrete
Regarding isolation techniques, if high concentrations are not to be feared, isolation – it is underlined in the plan – can be guaranteed by the same underground structure if made entirely of reinforced concrete.
7 | Anti-humidity techniques
Another noteworthy information given in the annex to the Plan concerns the measures adopted to protect buildings from humidity. Despite the greater possibility of diffusion and permeability of radon compared to water vapour, «in general it should be considered that the techniques used against humidity are usually also effective against radon».
8 | Pressure difference between inside and outside
Radon, if present, spreads in buildings from rooms in contact with the subsoil due to the pressure difference between the subsoil and the inside of the building and as a result of the thermal gradient. Therefore – it is highlighted in the Plan -, «intervention strategies aimed at modifying the pressure difference between the inside and outside of the building have all the potential to prove quite effective in combating the infiltration of strong concentrations of radon». These are effective interventions, especially in new buildings, while for renovations they can lead to costs that are not sustainable or not at all sustainable.
In any case, the ventilation can be passive (the natural thermal gradient is exploited) or active (ventilation systems are used). «For new buildings, especially when significant problems related to radon are conceivable, it is advisable, already in the initial design phase, to set up the technical planning of the interventions by providing a system of arrangements that allow in the future, once the work has been completed, the possible installation of a ventilation system. For example, during the construction of the foundations, install a system of flexible micro-perforated pipes, connected to one or more wells external to the building (radon wells), where, if necessary, an adequate ventilation to extract any excess radon”.
9 | Drainage and radon wells
Among the ventilation techniques for the ground beneath the building, the Plan, in addition to adequate ventilation of the crawl spaces, indicates various actions, including: the drainage under the base of the building and the creation of collection wells under the floor of underground rooms. In the first case it involves creating a system of drainage pipes or channels, with the lower part perforated in order to convey and remove the radon present; the continuous presence of air saturated with radon makes this technique plausible only if it is also possible to create a generalized depression with respect to the underground spaces above (for example, by placing a waterproofing sheath between the ground and the pipes, which hinders the flow of air saturated).
The creation of one or more collection wells under the floor of underground rooms (“radon wells”) complete with pipes (possibly equipped with fans) can be useful for removing radon outside; these wells must however be provided in combination with a crawl space drainage system.
10 | Monitoring during construction
Regardless of the techniques chosen, the document recommends providing adequate monitoring both during construction and at the end.
«During construction, the protection measures against radon – it is specified in the Plan – must be the subject of attention by the works management and the tester. In particular, it is necessary to carry out intermediate checks, if not actual partial tests, of the measures implemented, as well as measurements of the actual radon concentration. Finally, only after having verified that the work has been carried out correctly and in a workmanlike manner, will it be possible to proceed with the execution of further work which entails covering up the work carried out and which prevents further checks”.
Furthermore, in the Plan it is recommended that the «verification phases during construction are contractualized in the special tender specifications or in specific procedures and operating instructions, preferably within the quality management system dedicated to the realization of the works» .
«Similarly, once the works have been completed, the final verification of the effectiveness of the interventions must be entrusted to the specific activity and responsibility of the tester, also through measurements of the actual radon concentration, continued for an adequate time in relation to the final testing operations of the works. Furthermore, it is desirable that subsequent measurements of the radon concentration, on a periodic basis, are part of the checks planned within a use and maintenance program for the work”.
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published on: 11/03/2024