Radon and construction features Do solid concrete floors offer greater protection against radon than timber floors ? There is no clear answer to this, radon can enter a house through cracks and gaps in and around both concrete and timber floors. Whilst it might appear that a timber floor will be more leaky, they also have a ventilated void below to prevent timber rot, which can help to dilute radon. I live in a radon affected area and the house I live in is built of local rock will this influence the radon level in my house ? The main source of radon is the ground below the home. Stone walls and fireplaces do not emit much radon. My house has a stone fireplace is this the cause of my radon problem? The main source of radon is the ground below the home, stone fireplaces do not emit much radon Protection of new buildings, extensions and conversions New Buildings Where can I get information on radon protection for new buildings? The current requirements and technical solutions are contained in BRE Report BR211 Radon: Guidance on Protective measures for new dwellings. Building Control have told me that I need a radon site report, where do I get one from? A Radon Protection Measures geological assessment can be obtained from the British Geological Survey, Keyworth, Nottingham, BNG12 5GG. Telephone 0115 936 3192, or e-mail: enquiry@bgs.ac.uk Other institutions such as universities may also be able to provide this information locally. Building Control have told me I need to install basic radon protection what do I have to do? You will need to provide a radon barrier across the footprint of the building. Building Control have told me I need to install full radon protection what do I have to do? You will need to provide a radon barrier across the footprint of the building and provision for future subfloor depressurisation or pressurisation by providing underfloor ventilation to suspended concrete floors or a radon sump. What is a radon sump in a new building? A radon sump is a small void, about the size of a bucket, constructed beneath a floor slab. Typically formed using bricks and a paving slab or a prefabricated sump unit the sump is linked to the outside of the building by a length of pipe which is then capped. If an elevated radon level is measured on completion of the building the cap can be removed and a fan attached to reduce radon levels. Do I need to provide a fan and a sump during construction? Only the sump needs to be installed during construction, it is up to the occupier to install the fan later if the house is found to have an elevated radon level. I am upto first floor level with the brickwork and have now been told that I need to provide radon protection what can I do? In-situ concrete floor : It is too late to provide a radon barrier within the concrete floor. However you could try to seal floor to wall joints with a gun-applied sealant prior to installing skirtings. This will not provide the protection of a full barrier but should help to reduce radon entry. You can also provide a sump. To confirm whether or not the sump needs to be activated the house should be tested on occupation. Suspended beam and block concrete floor : A barrier could be laid across the floor  and sealed to the walls with a gun-applied sealant prior to installing the floor topping. This will not provide the same effectiveness as a full barrier but should help to reduce radon entry. In addition make sure that the underfloor void is well ventilated. The house should be tested on occupation and if found to have an elevated radon level a fan installed to further ventilate the underfloor void. I have nearly completed construction of a new house and now Building Control have told me that I need to provide radon protection. It is too late to provide a radon barrier within the floor the only realistic option is to test the completed house on occupation. If an elevated radon level is found the builder should install appropriate remedial measures - probably either a sump system (with the sump excavated through the external wall from outside) , or increased ventilation to a subfloor void. Extensions Do extensions have to incorporate radon protection? The guidance contained within BRE Report BR211 Radon: Guidance on Protective measures for new dwellings applies to all extensions to dwellings except where an exemption is provided in Schedule 2 of the Building Regulations. Do I need to obtain a geological assessment for an extension? There is little benefit to be gained by obtaining a geological assessment of sites in light grey squares in Annex B as the radon barrier is unlikely to cost more than the assessment. Do I need to provide full radon protection in my extension? The necessity of providing full radon protection (radon barrier and sump) is a matter of judgement for the Building Control Body. Large extensions that are designed to provide only ancillary accommodation may be re-arranged in the future to provide living accommodation. The size of the extension may be an indicator. If the extension is less than half the ground floor area of the existing house or 30m2, whichever is smaller, it could be considered to be relatively small.  However, if the accommodation is designed as habitable space in the first instance radon protection should be provided at the appropriate level unless it is considered that full protection is not of significant benefit in which case dispensation under Regulation 8 could be considered. My extension is very small do I need to include full radon protection? Extensions with a ground floor area of more than half the ground floor area of the existing house or 30m2, whichever is the lesser, should have full radon protection if the house is in a dark brown square in Annex A or if a geological assessment indicates that full protection is advisable. My extension is very small do i need to include full radon protection? If the extension is only to be used as a porch, utility room or cloakroom/ shower room occupiers are unlikely to spend much time in these parts of their home. In these circumstances it may be possible to set aside full radon protection if it does not exceed the ground floor area criteria but this is a matter of judgement for the Building Control Body. In such a case there may be no need to obtain a geological assessment or to provide a sump, as it would be of marginal benefit when considered with the risk to the whole of the house. How can I seal the joint between the new extension and original building? One option is to cut a chase in the existing wall and then to tuck and seal the radon barrier into the chase.  Whilst this is probably the best approach, other methods of joint sealing maybe be used e.g. bathroom sealant or other flexible filler. If my house does not have a radon problem do I need to provide radon protection within the extension ? If a three month test result shows that radon levels in the home are well below the action level radon protective measures may be omitted from the extension. But if the result exceeds the recommended action level of 200 Bq/m3 appropriate protection measures should be installed within the extension and radon reduction measures provided in the existing part of the house. Conversions The Building Control Officer has told me to provide radon protective measures in the barn that I am converting, what can I do ? If you are installing a new concrete ground floor you can install a radon barrier within the floor. Whilst the barrier will protect the bulk floor area radon could bypass the barrier and enter through the joint between the floor and wall. You could try to seal this joint using a gun-applied sealant. Even then radon might still enter via the old walls. As a consequence it is advisable to also provide a sump beneath the new floor so that If it proves necessary later a fan can be fitted to lower the radon level. Reducing Radon levels in existing buildings Sumps How does a sump system work ? A radon sump is essentially a hole in the ground with a fan connected to it sucking from the hole and thus producing a negative pressure in the hole. This negative pressure spreads through the pore spaces in the material immediately under the floor. The purpose of the radon sump is to reverse the air pressure between the soil and the dwelling and to stop the radon laden air from entering the dwelling. Due to their depressurising effect sump systems are sometimes referred to as sub-slab depressurisation systems. How much does a sump system cost ? The NRPB suggest the average price to be £750 - £1000. Actual costs will be dependent upon the construction and layout of the property. Are sump systems noisy ? Inevitably there will be some sound from a fan powered sump system. But if care is taken in locating and installing a system it should not prove unacceptably noisy. Do sump systems have to run continuously ? In most cases the fan will need to run continuously. There is limited experience of the effectiveness of running fans Intermittently, but it is known that frequent starting and stopping is more likely to result in premature fan failure. Trials have shown that radon can return to its original elevated level within a matter of a few hours of switching the fan off. Do I have to have a fan on my sump system? It is sometimes possible to use the natural stack or chimney effect of the building to drive a sump system and so avoid having to use a fan. This is called a passive sump system. To be effective it usually has to be located within the building with a vertical stack pipe routed up through the building and exhausting above the roof. When can I use a passive sump system? They are ideally suited to bungalows and have been used successfully with radon levels between 200 Bq/m3 - 700 Bq/m3. The important point is that if they fail to adequately reduce the radon level they can be upgraded by adding a fan. Do all sump systems have to have a pipe up the outside of the house? No, it maybe be possible, particularly with a bungalow, to route the pipework up the inside of the property. Alternatively if there are no doors, windows, or other openings such as vents adjacent to where the fan is located it can exhaust at ground level. What is a condensate drain ? It is small device, fitted just above the fan in the stack pipe, used to drain moisture away from the fan. Where can I get a fan for a sump system? Most major manufacturers who market kitchen and bathroom extract fans can supply centrifugal in-line duct fans suitable for use on radon sump systems. Local builders merchants and electrical suppliers may stock suitable fans. Can the fan blow into the sump? In areas where the soil or fill beneath the building is highly permeable blowing can work better than sucking. Usually fans are installed in suction and only reversed to blow if suction fails to reduce the radon level. Where can I get more information on radon sump systems? Further information is contained in BRE Report BR227:  Radon sump systems: a BRE guide to radon remedial measures in existing dwellings Increased underfloor ventilation How can I increase the underfloor ventilation in my home? You can increase the natural underfloor ventilation by providing additional underfloor vents, or replacing old terracotta vents with new louvred plastic vents. This 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 or the property large you may need to use more than one fan. Where can I get more information on increasing 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 Positive pressurisation systems How does positive pressurisation work ? Positive pressurisation works by taking air from the loft space, or from outside, and blowing it into the house. This creates a very slight pressure which can be just enough to counter the natural stack or chimney effect which draws radon into the house from the soil. At the same time the additional air being blown into the house has a diluting effect on the radon. How effective are positive pressurisation systems? They are generally effective only at moderate radon levels, up to about 700 Bq/m3, and work best in more airtight dwellings. How much do positive pressurisation systems cost? The units themselves range between £250 and £500. There will be an additional cost for installation, but they are relatively easy to install so can be carried out on a DIY basis. How much do positive pressurisation systems cost to run? The latest systems are advertised as costing no more than a couple of pence per day to operate. Do positive pressurisation systems offer any benefits other than radon reduction ? Yes. They are widely used to reduce condensation in homes. They can be used to resolve both a radon and condensation problem in a house. Are positive pressurisation systems noisy? Inevitably they will generate some noise, but when sited away from noise sensitive locations and appropriately mounted they should not prove unacceptably noisy Where can I find more information on positive pressurisation systems? Further information is contained in BRE Report BR281: Positive pressurisation: a BRE guide to radon remedial measures in existing dwellings Sealing floors and Walls How effective is sealing cracks in floors and walls? Generally, it is difficult to reduce the radon level to much less than half by this means. It is likely to be effective only at moderate radon levels, upto 400 Bq/m3. Sealing is usually only recommended where there are obvious large openings through the floor i.e. bits of floor boarding missing, large openings around service pipes, or large cracks around concrete floors. It is difficult to ensure that you have successfully sealed all gaps and cracks. How can I seal a suspended timber floor? Complete sealing of timber floors e.g. with a continuous polyethylene sheet,  is not recommended, as it may cause excessive moisture movement or induce timber rot, although sealing of large holes is appropriate. Would sealing the walls and floors in my cellar be effective ? 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, e.g. where walls and floors are being tanked to prevent moisture entry. Where can I get more information on sealing cracks and gaps in floors? Further information is contained in BRE Report BR239:  Sealing cracks in solid floors: a BRE guide to radon remedial measures in existing dwellings Natural house ventilation Will opening windows more often reduce radon levels? Simply opening windows is unlikely to have a significant long term effect, in fact in some cases opening windows can actually increase radon levels. Is it possible to change the way in which I ventilate my house to reduce the radon level? It may be 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 . How can I change the way I ventilate my house to reduce radon levels? Typical examples of appropriate measures include installing trickle ventilators to windows, particularly downstairs, capping off and sealing unused chimneys, draught stripping loft hatches and avoiding use of open fires and solid-fuel-effect open fires. Contact the BRE Radon Hotline for more advice. Is it worthwhile trying to increase the ventilation to my cellar? 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 Should fans used to ventilate cellars extract air out or blow fresh air in ? There is no clear answer, both have been found to be  effective in reducing radon levels to the rest of the building. However it is important to note that a fan extracting air from a cellar will increase the radon level within the cellar itself even though it may reduce levels in the house above. As a consequence if the cellar is likely to be used on a regular basis we would recommend blowing air into the cellar, or to use an alternative solution such as a sump system. Where can I get more advice on reducing radon levels in a house with a cellar? Further advice is contained in BRE Report BR343:  Dwellings with cellars and basements: a BRE guide to radon remedial measures in existing dwellings. Can ionisers, electrostatic precipitators or air cleaners be used to reduce radon levels ? None of these devices are very effective when compared with other solutions If you would like to speak to somebody about radon in the first instance please phone the Health Protection Agency Radon Hotline on 01235 822622. Arron Perry | May 2005 | © copyright BRE 2000