Radon enters a dwelling primarily by airflow from the underlying ground. There are two main methods of achieving radon protection in new dwellings: passive and active.

• The passive system consists of an airtight and therefore substantially radon-proof barrier across the whole of the dwelling including the floor and walls.
• The active system consists of providing natural or mechanical underfloor ventilation, or a powered radon-extract system as an integral part of the services of the dwelling. These two options will incur running and maintenance costs for the life of the building.

Passive systems are to be preferred in new dwellings, although they may need to be supplemented by active protection, involving for example underfloor ventilation or subfloor depressurisation.

Passive radon protection systems can be divided into two types Basic radon protection and Full radon protection.

Basic Radon Protection
In areas where there are lower levels of radon it is recommended that a radon barrier should be laid within the floor construction and linked to the damp proof course laid within the walls of the dwelling. As most solid ground floors already incorporate a damp proof membrane this is not a great change from current construction practice except that to be gas tight the joints must be sealed and any penetrations through the floor should be avoided or if they must occur they must be effectively sealed. Additionally, gas should be prevented from entering via the cavity by the provision of a cavity tray.

Full Radon Protection
In higher risk areas a higher standard of protection than that offered by a radon barrier is needed. There is no difference in the provision of radon barriers than those for areas of lower radon levels, but the barrier must be supplemented by provision for subfloor ventilation or subfloor depressurisation. This supplementary protection is provided in high risk areas to reduce the amount of radon the barrier has to exclude but it should not be looked upon as a primary defence. Radon dispersion systems are useful in high radon areas because they assist in reducing radon levels to a point where the membrane has a better chance of keeping the radon intrusion into the dwelling down to an acceptable level. Supplementary protection may be immediately effective in the case of sub-floor ventilation but sub-floor depressurisation will require the use of a fan to remove the radon.