RADON Just Another Ground Gas? Peter Atchison Managing Director PAGeotechnical Ltd Chair of The Radon Council

Bulk gases: Methane, Carbon Dioxide •NHBC - Guidance on evaluation of development proposals on sites where methane and carbon Dioxide are present Report No 10627-RO1 (04) January 2007

•CIRIA - C665 Assessing Risks posed by hazardous ground gases to buildings 2007

•BS8485 – Code of Practice for the characterisation and remediation from ground gas in affected developments Dec 2007

VOC/s Current work By CIRIA

RADON •BRE 211……………. 1990’s and discredited

•Missed out of the Building regulations revision last year -

Is Radon treated as a second rate risk ?

The ground gas hierarchy

• A naturally occurring element • A radioactive gas • Colourless & odourless • Comes from radioactive decay of Radium • Radium comes from radioactive decay of uranium

What is RADON?

• Uranium is a permanent source of radon, and found in different quantities in rocks & soil

• Some areas are therefore free of radon, while others have uranium-rich rocks which emit radon

• Radon escapes naturally from rocks beneath the earth's surface

Radon

Gas Percentage by volume Nitrogen 78.08 Oxygen 20.95 Argon 0.93 Carbon dioxide 0.033 Neon 0.0018 Helium 0.00052 Krypton 0.00011 Hydrogen 0.00005 Xenon 0.0000087 Radon <0.000000000000000001

Concentration of gases in the atmosphere (excluding water vapour)

• Radon gas seeps into enclosed spaces (e.g. Buildings), and collects.

• Basements are particularly susceptible to large accumulations (as greater area in contact with soil)

• High concentrations can build up, depending on local geology, atmospheric conditions & ventilation

• Radon decays to form short-lived radioactive particles, which remain suspended in air

• When inhaled, these irradiate the lungs and increase risk of developing lung cancer

Mechanism of harm

• Radon gas levels can be measured • Levels can vary in different locations within a

single building • Risk increases with radon level & duration of exposure • High radon levels therefore need to be treated seriously

and steps taken to ensure exposure is kept as low as reasonably possible

Finding and measuring

• Average UK background radon concentration outside is 4 Bq m-3

• Outside, radon gas dissipates harmlessly • Average level inside UK homes is c20 Bq m-3 • For levels below 100 Bq m-3, individual risk remains

relatively low • However, risk increases as the radon level increases

RADON Levels

• Government recommends that radon levels should be reduced in homes where the average is more than the Action level of 200 Bq m-3

• The Target Level of 100 Bq m-3 is the ideal outcome for remediation works in existing buildings and protective measures in new buildings

• If the result of a radon assessment is between the Target and Action Levels in homes, action to reduce the level should be seriously considered, especially if there is a smoker or ex-smoker in the home

Target and Action radon levels

• Current Action level is 400 Bq m-3 in commercial properties

• Action is required at this level in commercial properties

Commercial properties

Radon deaths – compared to other causes of UK premature deaths per year

Radon exposure risks

Methods of protection

There are two main methods of dealing with Radon in new buildings •Basic radon Protection: Airtight gas resistant barrier across or through the floor of the building continuous to the outer leaf of the exterior walls

•Full Radon Protection: Provision made for future active system, usually consists of a radon sump with extraction pipe (or underfloor ventilation) Householder provides fan at later date

• Laying Radon resisting membranes across the entire floor areas of buildings is only possible during construction

• Specialist membranes may be used but 1200g polythene sheet may be considered adequate.

• Alternative specialist barriers may comprise: • Prefabricated welded proprietary membranes • Liquid Coatings • Asphalt • Self Adhesive bituminous coated sheet products

Basic protection

• It is acknowledged that achievement of a totally airtight radon barrier is difficult therefore additional (ventilation) measures are also used.

• Natural ventilation for suspended floors • Provision for future mechanical under floor ventilation

(Installation of airbricks and future mechanical ventilation)

• Provision for future sub-floor depressurisation of ground contact floors (Radon sump)

Secondary protection

• Specialist gas resistant membranes • Self adhesive / Spray applied coatings • Reinforced polymeric membranes • Basic single process blown film • Whatever the material this is not a benign environment!

Membrane materials

Full radon protection

• In a house with a ground bearing slab the radon sump will usually be installed in the permeable hardcore under the floor slab

• Where clean hardcore is used a single radon sump is likely to have an influence over an area of approximately 250m2 and for a distance of up to 15m from the sump. Obstructions below the slab will reduce the effectiveness and it may be necessary to provide free airways in rising walls etc

• A gap of 12,500mm2 per meter run of wall (1/4 block per 4 blocks) should be adequate

Radon sump…..

• Type of Protection (Basic / Full) • Membrane choice • Detailing / Design • Installation / Installation / Installation • Validation • Protection is only as good as its weakest part. • “Right First time” saves cost!

Things to remember!

Existing Buildings

∗ Most of the Radon risk in the UK will relate to existing building stock

∗ New buildings can be dealt with as from tomorrow! ∗ Existing stock will take longer! ∗ Requires acceptance of the problem ∗ Voluntary – Conveyancing ∗ Involuntary - Litigation?? ∗ Solutions exist!

A List of Typical Techniques Remedial Technique Radon Reduction

Factor*

Sealing floors (and/or loft hatch!) 1.2

Passive internal ventilation 1.3

Active internal ventilation 2.1

Passive under-floor ventilation 1.7

Active under-floor ventilation 2.2

Passive sump (inside) 1.9

Passive sump (outside) 1.8

Active sump 6.0 SOURCE: CRCE-019 An Analysis of Radon Remediation Methods HPA 2011

*Average achieved Not an exhaustive list

Sealing Cracks and Penetrations

∗ Done with off the shelf sealant products or closed cell foam for larger holes

∗ Difficulties are finding them all, some fine cracks are not detectable, others inaccessible or hidden without stripping out all fixtures and fittings

∗ Radon Reduction Factor – up to 3 (in the best cases)

∗ No good or limited impact on timber floors, or heavily cracked slabs or block and beam – need membrane (not with timber floors though!)

Passive Internal Ventilation

∗ Window Trickle Vents ∗ Opening Windows ∗ Wall mounted open vents ∗ Positioning important

Not much good for keeping those heating bills down over winter!

Active Internal Ventilation

∗ Ducted Fan units ∗ Positive Pressure ∗ Power connections ∗ Positioning important ∗ Can have heat recovery ∗ Fan noise

Non heat recovery versions even worse for keeping those heating bills down over winter!

Positive Pressurisation (Ventilation)

∗ Achievable Radon Reduction Factor between 3 to 4

∗ Typically fitted in the loft ∗ Can have heat recovery ∗ Filtered air blown into the

property which provides a positive pressure – reducing and hopefully preventing Radon seeping in from the floor

Active Air Curtains

∗ Fairly new to market ∗ Very good solution for cellars (and

where water vapour resistance is required)

∗ Need walls/floors stripped where it is to be used

∗ Pressure Delivery Unit blows clean air into the cuspated void former, exhausted to atmosphere

Passive Underfloor Ventilation

∗ Standard sub-floor void and air bricks

∗ Low maintenance solution ∗ Care needs to be taken to ensure

all sleeper walls have sufficient ventilation

∗ Including a oversite improves performance

∗ Swapping old for new can increase performance

Active Underfloor Ventilation

∗ Plugs into sub-floor void / granular blanket

∗ Care needs to be taken to ensure all sleeper walls have sufficient ventilation

∗ Including a oversite improves performance

∗ Can reduce floor temperatures in winter

Passive Sump Systems

∗ Ducting needs to be raised to the low pressure area at eves / roof level

∗ Can be improved with a rotating cowl

∗ Can be made ‘active’ ∗ Placing important

Active Sumps

∗ The highest Radon Reduction Factor of all methods

∗ Typically to only viable solution where Radon is >1000Bqm-3

∗ Needs to be maintained ∗ Consider telemetry / alarm

systems for higher risk sites

Not Everything Works First Time

∗ Retrofitting Radon exclusion measures is not always straight forward

∗ Buildings can have complex or unusual designs, alterations, and differing foundations and floors

∗ You may need to use more than one protection technique

∗ Systems may need to be increased and/or tweaked (sometimes it can take 3 or 4 attempts!)

• Radon is a Gas and comes from the ground • It can be dealt with by modifying existing solutions,

developed for other bulk gases. • Whilst not the catastrophic risk associated with

explosive gases – RADON is a contributory factor in c.2,000 deaths in the UK per year.

• JUST another ground Gas Or the primary one? • What do you think?

So is RADON Just another Ground gas?