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Reducing 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. For advice on measurement contact http://www.ukradon.org/.

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.


sump1 external fan
External mini-sump External fan
 sump 2  Roof fan
Internal mini-sump Roof-space fan































Further information is contained in BRE Good Repair Guide GRG 37 Part 3 Radon solutions in homes: Radon sump systems

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.

Vent  Underfloor fan  
Poor underfloor vent  Fan to increase underfloor ventilation











Further information is contained in BRE Good Repair Guide GRG 37 Part 1 Radon solutions in homes: improving 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.

Vent Fan  Vent fan 
 Positive pressurisation system components  Positive pressurisation system















Further information is contained in BRE Good Repair Guide GRG 37 Part 2 Radon solutions in homes: positive house ventilation

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.

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

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.