How to reduce radon levels in your home

What is your radon level ?

Before you can consider how to reduce the radon level in your home you must have a reliable radon measurement taken.

This will usually comprise a whole house average reading based upon a pair of detectors placed in the main living room and main bedroom. For most homes this average reading will be adequate for helping to select appropriate remedial measures. Larger houses or houses of unusual layout or construction may need additional measurements to help target remedial measures. top
For advice on measurement contact the NRPB.

Radon solutions

There are five main ways of reducing the amount of radon entering a house:
- Installing a radon sump system
- Sealing floors and walls
- Increasing underfloor ventilation
- Installing a whole house positive pressurisation or positive supply ventilation system
- Improving the ventilation of the house

These solutions are not all suitable for all types of house, nor are they suitable for all levels of radon, and in some cases more than one solution will need to be used in resolving the radon problem. This is particularly the case where a house is large or it has a cellar or basement. The five methods are briefly described here, together with an indication as to the radon levels that can be reduced. top

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/m3 it is sometimes 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. top

 

Above: external mini sump system	external fan
Above: internal mini sump system	Roof space fan

Further information is contained in BRE Report BR227: Radon Sumps: a BRE guide to radon remedial measures in existing dwellings, available from BREbookshop.com

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, upto 400-500 Bq/m3. 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. top

Further information is contained in BRE Report BR239: Sealing cracks in solid floors: a BRE guide to radon remedial measures in existing dwellings, available from BREbookshop.com

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 upto 700 Bq/m3. Higher radon levels can be dealt with by increasing ventilation using a fan. If the levels are very high - 1000 Bq/m3 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 provide increased underfloor ventilation

Further information is contained in BRE Report BR270: Protecting dwellings with suspended timber floors: a BRE guide to radon remedial measures in existing dwellings, available from BREbookshop

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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. The technique was originally developed to reduce condensation problems in homes. The method is generally effective only at moderate radon levels, up to about 700 Bq/m3, and works better in more airtight dwellings.

Positive pressurisation system components
	Positive pressurisation system

Further information is contained in BRE Report BR281: Positive pressurisation: a BRE guide to radon remedial measures in existing dwellings, available from BREbookshop.com

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/m3 . Typical examples of appropriate measures include installing trickle ventilators to windows, capping off and sealing unused chimneys, draught-proofing loft hatches 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. top

Other information

Further information is contained in the following guides available from BREbookshop.com

BRE Report BR250: Surveying dwellings with high indoor radon levels: a BRE guide to radon remedial measures in existing dwellings

BRE Report BR343: Dwellings with cellars and basements: a BRE guide to radon remedial measures in existing dwellings

Good Building Guide 26 : Minimising noise from domestic fan systems.