Precautions against radon
As radon is a contaminant, it falls under requirement C3 of the building regulations that states, “Reasonable precautions shall be taken to avoid danger to health and safety caused by substances (including contaminants) found on or in the ground being covered by the building.”
It is stated in Approved Document C of the building regulations that measures should be taken to protect new buildings from radon entering from the ground.
New builds, high-radon areas
Any area where the British Geological Survey (BGS) indicates that more than 10% of the houses are likely to have a radon level exceeding the National Radon Level (NRL) of 200 Bq/m^3^ are considered high radon areas.
The provision of a sealed radon membrane of low permeability combined with a potential means of extracting radon from the substructure such as a standby sump or sumps with connecting pipework is a typical method of protection. If a post-construction survey indicates that the actual radon level is greater than the NRL, the sump(s) can be activated by the installation of a fan.
New builds, normal radon areas
Any area where the BGS indicates that less than 10% of the houses are likely to have a radon level exceeding the NRL of 200 Bq/m^3^ are considered outside high radon areas.
A sump(s) along with connecting pipework terminated and capped at appropriate points outside the external walls or in the attic space should be provided. Clear and permanent markings should be placed on the pipe terminals from the radon sump that state their functions. If a post
construction survey indicates that the actual radon level is greater than the NRL, the sump(s) can be activated by the installation of a fan.
Radon solutions
There are essentially three generic solutions that can be applied to a building, either independently or in tandem, to reduce indoor radon levels.
Sump system Effective for all radon levels
Improved under floor ventilation Natural under floor ventilation generally effective for radon levels up to 500 Bq m-3, mechanical ventilation effective for all radon levels.
Positive house ventilation generally effective for radon levels up to 500 Bq m-3.
These can be supplemented with:
Improved house ventilation
Simple sealing
Radon sump
If your home has a solid concrete ground floor you can extract the radon laden air from beneath the floor (depressurising the soil) by using a radon sump. This is generally the most effective method, and in many cases will reduce the radon level to less than one-tenth of the original level. For radon levels above 1200 Bq m-3 it is often the only solution.
Although principally appropriate for solid floors, a sump can be used with a suspended timber floor if there is a layer of concrete or a membrane covering the soil beneath it. In some cases blowing into the sump and pressurising the soil can also prove effective.
External mini-sump
External fan
Internal mini-sump
Roof-space fan
Increased underfloor ventilation
With a suspended floor you can increase the flow of air beneath the floor. Increasing the natural underfloor ventilation by providing additional underfloor vents, or replacing old terracotta vents with new louvred plastic vents can prove effective and has been used with levels up to 700 Bq m-3. Higher radon levels can be dealt with by increasing ventilation using a fan. If the levels are very high - 1000 Bq m-3 or more you may need to use more than one fan. This solution is unlikely to be appropriate for use in houses with full cellars or basements.
Poor underfloor vent
Fan to increase underfloor ventilation
Positive pressurisation or ventilation
You can pressurise the house using a fan which draws air from the loft space or from outside and blows it indoors. This method is again generally effective only at moderate radon levels, up to about 700 Bq m-3, and works better in more airtight dwellings.
Positive pressurisation or ventilation
You can pressurise the house using a fan which draws air from the loft space or from outside and blows it indoors. This method is again generally effective only at moderate radon levels, up to about 700 Bq m-3, and works better in more airtight dwellings.
Positive pressurisation system components
Positive pressurisation system
Sealing floors and walls
You can seal the floor and the joint between the floor and wall, to prevent the radon getting through gaps and cracks. It is likely to be effective only at moderate radon levels, up to 400-500 Bq m-3. Generally, it is difficult to reduce the radon level to much less than half by this means. Complete sealing of timber floors e.g. with a continuous polyethylene sheet, is not recommended, though the sealing of large holes is appropriate. Major sealing work to walls and floors in cellars and basements is usually only a viable option where it forms part of work being carried out to convert an unused space into occupied space.
Improving the ventilation of the house
In some cases it is possible to change the way in which you ventilate your home to help avoid drawing radon up through the floor or walls of the house. However as this depends on the way in which you live in the house it is not generally a reliable method. It may be suitable for radon levels up to 400 Bq m-3. Typical examples of appropriate measures include installing trickle ventilators to windows, capping off and sealing unused chimneys, and avoiding use of open fires and solid-fuel-effect open fires.
If the house has a cellar or basement improved natural or mechanical ventilation targeted on the cellar or basement, where the highest radon levels are likely to be, can prove extremely effective, and offer large radon reductions. Mechanical fans can be used to blow air into, or draw air out of, a cellar or basement.
Information from www.bre.co.uk/radon
