THE RADON COUNCIL’S
GUIDANCE NOTES FOR RADON BARRIERS
Introduction
This non-profit making self-regulatory body was formed in 1991 in response to recommendations contained in an Interim Report of the House of Commons 6th Report of the Environment Committee on Indoor Pollution. It is not a commercial trade association.
The Radon Council is concerned that a significant minority of new homes allegedly complying with Building Regulations will frequently include a “radon membrane” and some even a “radon sump”. Experience shows that unless these are specified and correctly installed, high radon levels can still occur.
Although the installation of a radon barrier is a mandatory requirement in areas of the UK designated as “affected” the Radon Council recommends that in the interests of “best practice” the installation of a barrier should be considered in all areas at the time of new build. This is because isolated high levels of radon can be found in the so called “non-affected areas”.
The following guidance may help builders and others to obtain the considerable technical expertise to ensure that barrier work is effectively carried out. It has to be recognised that, except for certain areas in the UK, there is considerable ignorance about radon and the need to begin to stop the avoidable annual death rate from this naturally occurring radioactive gas venting from anywhere on the Earth’s crust.
The full requirements for compliance with the building regulations can be found in the BRE Ltd document “Radon: guidance on protective measures for new dwellings BR211”.
Where to go for help?
The Radon Council publishes an annual List of competent contractors and radon testing services. This list is revised and monitored every year and can be found by visiting the Radon Council’s website www.radonhotline.org or by telephone 01932 221212. Such contractors on the Radon Council’s annual list have signed a contract that they will:-
(a) abide by national and any relevant local legislation,
(b) follow the Council’s Code of Practice and Radon Manual,
(c) have at least one responsible employee who has attended the full training course and passed the examination for which a certificate is issued.
The Radon Council has a disciplinary group including a lawyer to resolve any conflicts between consumers and contractors. The Council reserves the right to exclude any offending contractors from its annual list.
Radon Barriers.
Why use a Radon Barrier?
Naturally occurring radioactive radon gas is a breakdown product of radioactive uranium in the Earth's crust. It is a known carcinogen and poses a chronic toxicity hazard to man.
Radon is responsible for some avoidable 2,500 deaths a year from lung cancer in the UK.
Geological studies and maps can only provide a rough guide to heavy pockets of the gas and never an accurate figure on the radon level in any one specific home or workplace.
Because radon enters a building from the ground on which it is built, the most effective method of reducing indoor levels, is by preventing it entering the building in the first place.
Recently published research indicates that a significant health risk exists at levels of radon lower than the current action level and the need for effective and improved protection is increasingly important.
What is a Radon Barrier?
This is a fully sealed very low gas permeability barrier (sometimes referred to as a membrane) placed over the entire footprint of the building at the time of construction. In some cases it can be provided in lieu of the damp-proof membrane, but other such building features are generally ignored in this document. These guidance notes are restricted to the purposes of radon protection. It is important that the requirements of the radon barrier are considered during design.
The requirement of a radon barrier is to prevent any radon gas entering into a property. It follows therefore that the material used, must be adequate for the task and fulfil several criteria:
1) Easily packed and protected during manufacture, storage and transport,
2) Sufficiently robust and impervious to the gas,
3) Sufficiently strong to withstand the installation process and following trades until covered, and
4) Capable
after a skilled installation of providing
a complete barrier
to the entry of radon gas.
The Installation of Radon Barriers
The Barrier
The Barrier to radon gas (sometimes called a membrane) may be a proprietary barrier which is preferred to ordinary polythene, as it is normally of a superior quality. In some cases it is reinforced for additional strength and designed for the purpose. Whatever the material or construction the barrier must cover the whole footprint of the building including any external or internal cavities.
Procedures
It is important that the requirements of the radon barrier are considered at the design and layout stages. Care should be taken at the design stage to ensure that a structural slip plane does not occur. The advice in these notes also excludes the question of damp-proofing or water problems.
Care must be taken to ensure that the barrier is laid on well-blinded hardcore, suitable Geotextile, or cleaned and swept suspended floor that is free from projections, indentations, irregular or sharp finishes and should be inspected for damage prior to covering with slab or screed. Any damage should be repaired with barrier ensuring a 150mm lap. Where strips of barrier are incorporated into the external and internal walls at commencement, they must be suitably protected for the duration of the build until the main carpet of the barrier is installed. All laps and joints should for preference be welded or as a minimum requirement sealed with butyl jointing tape, (normally 50mm wide or as specified by the manufacturer) and not adhesive tape, The barrier should be dry and clean before sealing. All penetration for services and drains should be sealed using a preformed top hat, again welded for preference, or sealed to the barrier with butyl tape. Where there are cavity trays, pile caps or stanchions, advice should be sought from a specialist as to the best approach. Please see the Radon Council list on the main page for suppliers of materials. Corners can present difficulties; again, products are available to assist in achieving the integrity required.
Sump Installation
In some European countries (eg Ireland) new build requirements may include the building and sealing of a sump for any future remediation requirements that may be necessary. This makes good sense and is a negligible cost at the time of construction. Currently it is not a UK legal obligation other than in certain designated areas.
Conclusion
Because of the practical difficulties encountered on a building site the employment of specialist membrane installers and /or pre-fabrication should be considered. It can frequently be the most cost-effective option.
The key to installing a gas-proof barrier is attention to detail, and allowing sufficient time. Tell the installer the object of the exercise, and give them the correct materials, and above all else
Even small perforations in a barrier can in certain areas result in high levels of radon penetration and the integrity of a perfectly laid barrier can be compromised by subsequent actions.
Consideration must be given after installation to:
(a) Subsequent building modifications or the addition of extensions.
(b) Recent studies have shown following radon tests in “new-build” homes, that a large minority of new properties may have radon problems contrary to the aims of the legislation. The source of many such problems is probably due to faulty or incorrectly laid barriers, or, to finishing, plumbing, wiring and other operations that have damaged the integrity of the barrier work.
This means that it is essential for a radon test to be carried out on all finished properties, preferably before occupancy. Depending on circumstances, a reliable 7-day test, or, 3-months test can be used.
The validity and reliability of 7-day testing has again been confirmed recently by a comparison study of tests funded by DEFRA. The Council’s policy of “To Test is Best” applies to all homes (new or old) and workplaces.
The following Minimum performance levels for Barrier materials are an excerpt from Technical Guidance Document C, September 2004. Published by The Stationary Office – Dublin
Minimum performance levels for Low Density Polyethylene (LDPE) Membranes.
Certification of materials used for radon membranes should demonstrate compliance with the following parameters.
|
Parameter |
Test |
Performance Level of LDPE |
|
Radon Permeability |
Laboratory Test with Radon Gas – Rn 222 |
12X10-12m2/s |
|
Tensile Strength |
I.S. EN 12311-2:2000 or I.S. EN ISO 527-3 |
MD > 12Mpa CD > 12Mpa |
|
Elongation |
I.S. EN 12311-2:2000 or I.S. EN ISO 527-3 |
> or =100% (at break) Un-reinforced LDPE
> or =12% (at break) Reinforced LDPE |
|
Tear Resistance |
I.S. EN 12310-2:2000 |
>100N |
|
Moisture Vapour Resistance |
BS 3177 |
>50MNs/g |
|
Low Temperature Flexibility |
I.S. EN 495-5:2000 |
No cracking at –250 C |
and
Reproduced by courtesy of Department of the Environment, Heritage and Local Government – Republic of Ireland.
Useful Sources of Reference.
www.bre.co.uk
ODPM
www.odpm.gov.uk
www.defra.gov.uk
www.radon.co.uk
www.radonhotline.org
www.radon-one.com