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Land in the South West: Should we be worried about radon?

watch out for radon on a south-west plot

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Find land in the southwest is not always easy. In addition to theemplacement, theexposure, its size, we must also look at its nature and also the risks associated with it. Unknown to owners, the radon can sometimes be present on a the land. The presence of this radioactive gas should not be taken lightly when doing build his house. Should we be worried when we find ourselves in a radon potential zone ? Can we build ? What rules must the manufacturer follow for a healthy home ? We take stock in this article.


What is radon?

Le radon is a gas radioactive naturally present in the environment in greater or lesser quantities. It comes from the disintegration of uranium found more particularly in soils and granite rocks. Present everywhere in France, it presents health risks. Indeed, in a poorly designed house, the radon present in the ground can accumulate inside and reach excessive concentrations.


Land in the South-West with radon: what does the law say?

The decree of June 27, 2018 defined the radon potential areas across the national territory. This zoning, carried out by the Institute for Radiation Protection and Nuclear Safety (IRSN), thus identifies the risk for each municipality. It presents 3 categories of radon potential zones.

– Areas to low radon potential

– Zones with low radon potential but where specific geological factors can facilitate the transfer of radon to buildings.

- The areas with significant radon potential : the environment code includes radon as a natural hazard and therefore imposes buyer-tenant information in these so-called category 3 areas.

A interactive map is available on the IRSN website. Anyone can check if their future land and municipality are affected by the presence of this pollutant.

Map illustrating areas with high radon potential in the South West.

To go further, read the article: 10 questions to ask yourself when choosing the right building plot for your house »

Land in the South-West: What are the areas with radon potential?

Land in Occitania and radon zone

Le South West is for the most part not a region at risk. Nevertheless, some well-defined areas are classified in category 3. These will mainly be mountainous areas where the soils are often granitic: the Pyrenees and the central massif.
Framed by these two massifs, La region Occitania is thus the most affected with twelve departments out of the thirteen that make up the region which have municipalities classified in zone 3. Only the Gers and Tarn et Garonne are very little affected.

Land in Nouvelle-Aquitaine and radon zone

Less exposed, the region New Aquitaine also presents a radon risk throughout its territory, particularly in the formerLimousin and neighboring areas, north of Deux-Sèvres as well as in the south of Pyrénées-Atlantiques. The Gironde meanwhile, the Lot and Garonne and Landes are little affected. However, south of Arcachon bay, Gironde north of Landes, the territory is classified as zone 2. If the risk is not significant, it is therefore necessary to take these data into account to build the healthiest possible house.

Land in the South-West: what are the health risks of radon?

Radon is recognized by the International Agency for Research on Cancer as " carcinogenic lung certain”. Representing 5 to 10% of lung cancers, it is even the second cause of lung cancer behind cigarettes with an average of 2 cases/year in France.

The impact of radon on health, depends on its concentration in the air which is measured in Becquerel (Bq)/m3. In 2009, the World Health Organization recommended a reference level of 100 Bq/m3, and in any case to stay below 300 Bq/m3.

Is it forbidden to build on land with radon?

Of course, it is not forbidden to build on land with radon, insofar as a well thought-out house avoids high concentrations of this radioactive gas in the habitat. Nor is there any law that obliges you to build in this or that way. Thus, when one is in a municipality affected by this risk, it is advisable to respect certain rules oneself and to ensure the proper functioning of the installations so as not to harm one's health or that of the occupants of the house.

Radon enters the home mainly through the ground, then water and materials.
Leakage, water pipes… Radon enters the house by multiple routes

How to build a healthy house on land with radon?

Build an airtight house

To protect your home against radon risk, the risk of entry must first be reduced. Almost 80% of the radon present in the air of buildings comes from the subsoil. The other sources will then be the construction materials, outdoor air and water. To prevent radon from penetrating, a building must be particularly airtight, especially the surfaces in contact with the ground. Thus, sealing defects such as cracks in slabs, crossings of pipes, poor joints at the soil-building interface must be avoided so as not to allow radon the possibility of infiltrating inside the dwellings.

model crawl space ventilation
A ventilation grille allows the crawl space to be ventilated. This solution makes it possible to fight effectively against humidity but also against the accumulation of radon which could then penetrate into the dwelling.

Build a house with a crawl space

The houses built today under the aegis of the RE2020 are particularly airtight to minimize energy loss. Nevertheless, it is better to be cautious and avoid being immediately in contact with the ground. The simplest solution to guard against radon is still to build a house on a crawl space. The latter has many advantages in terms of humidity, in particular, but its protection against radon has also been proven. It is thus estimated that a crawlspace properly ventilated is enough to prevent radon from entering the home.

To find out more, read our article “ Sanitary space in a new house: advantages in the South-West »


Take care of air renewal

Either way, radon is getting into our homes. Odorless and colorless, it is practically undetectable. To prevent it from concentrating in our habitats, it is therefore necessary to avoid excessive concentrations. The latter will be higher the lower the air renewal. A system of ventilation performance will be essential. Single-flow mechanical ventilation ou Double-flow VMC will thus avoid excessively high concentrations of radon and other pollutants (VOCs, moulds, pollens, etc.) which deteriorate the indoor air quality and can harm people's health.

To find out more, read our article: How to ensure indoor air quality in a home »


Even with radon, a land in the southwest will accommodate your ideal home. The constructive solutions of builder Sic Houses aim to achieve healthy homes and sustainable for the daily comfort of the inhabitants.



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