Radon & Methane Gas IMPORTANT

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1 Radon & Methane Gas Radon Gas is everywhere - it is the extent that varies and structures are required to be built so radon exposure risk is minimised. IMPORTANT Every building must be designed and constructed in such a way that there will not be a threat to the building or the health of people in or around the due to the emission and containment of radon gas. 3.2 BR(S) mandatory. Every building must be designed and constructed in such a way that there will not be a threat to the building or the health of people in or around the building due to the presence of harmful or dangerous substances. 3.1 BR(S) mandatory. Whilst the applications described within this section refer predominately to radon gas, the design principals and functionality may be applied also to structures where methane gas presence demands footprint level arrestment as part of a fully appraised system.

2 Radon Gas Why is radon presence within a building best avoided? Radon remains the biggest single source of public radiation exposure in the UK. The World Health Organisation (WHO) and the International Commission on Radiological Protection (ICRP) have recently issued revised advice on protection against radon. The advice includes recommendations for revised reference (action) levels because radon has been recognised as being a greater risk to health than first thought. Those most at risk to radon radiation are those exposed to high concentrations. Therefore construction incorporating measures to reduce such levels is the objective. Dangerous to health? Radon is a natural radioactive gas and there is a risk of lung cancer largely attributable to inhalation of alpha-particle emissions from the radon decay products. The UK government figures acknowledge several thousand avoidable deaths per year are a consequence of exposure to radon. How is radon measured? Radon presence is measured in becquerels per cubic metre and ideally all domestic properties should have radon readings below 200 Bq m ³ which was once considered to be an acceptable / tolerable level. Whilst it remains the UK action level, a new figure of 100 Bq m ³ has been recently announced by the Health Protection Agency as the new target level. The definition of target being the level one should aim for. The reason for this is because there is now direct evidence of risk below 200 Bq m ³ Interestingly the action level for commercial properties is currently twice that of domestic Bq m ³ with an explanation that people are less likely to spend as long within a commercial property compared with a domestic property. Paradoxically commercial property includes buildings where inhabitants reside 24 hours a day, highlighting there is an imbalance of justification.

3 What are the Building Regulations? The Building Regulations require buildings being constructed on radon emitting ground to incorporate protective measures so that action levels (for the buildings) are not exceeded. Unfortunately with two UK levels (action and target) for both domestic and commercial properties, is there a danger the easier to meet action level will prevail and purchasers of new homes may not be afforded the level offering less exposure to risk? The current approach in the UK regarding to what extent a property is protected against radon places dependence on reference to maps. Unfortunately maps do not relate to the radon status of the land upon which the property is to be built but to the status of existing properties in the general area. As a consequence if low radon levels are shown on a map, a new property can be built without radon protection or with minimal radon protection. Only when the property has been completed is one able to really determine its radon contamination level. Prof William Angell, Chair of the World Health Organisation International Radon Project advises it is a long-term misconception that indoor radon is naturally occurring. Radon indoors is largely caused by the way homes are designed and built. The person(s) who put the building over the land are responsible. This prompts several important questions designer and developer should consider: Awareness of this health risk exists now, so have designer and developer a duty of care to ensure the purchaser/inhabitants of the building are not exposed to a health risk? higher than alternatives available that offer a better protected standard? How desirable will the property be if UK radon action levels are reduced further at some time in the future how will it compare? The response from most clients when asked to what extent a new property should be protected is that it should be to the safest and most practical level. Achieving this can be both straightforward and easy as it simply entails protecting the entire footprint of the building, from exterior face to exterior face. By so doing any radon in the ground under the building has reduced opportunity of entering and accumulating within the building. The current UK approach of relying on maps to provide the only guidance as to whether a structure should be protected against radon is flawed. Maps simply indicate whether there are structures in an area where radon tests have been carried out and elevated levels obtained. Maps do not take into account that modern structures by virtue of the new Building Regulations will be more airtight and unable to dissipate radon levels in the manner older structures permit dissipation. There is a danger that reliance on maps and the incorporation of some radon prevention measures only will be relied upon by designers, contractors and owners of property as being adequate to provide protection. Partial measures do not address cavities, and floor/wall interfacing, both of which are recognised radon entry routes. It is the person who puts the building over the land who is responsible. What will be the designers and developers position in the future regarding liability if the building (and thus its inhabitants) are not protected to the extent possible? Will the building asset value falter in the future if radon levels within it are higher than intended or Protecting the entire footprint of a building can remove chance from the radon equation. The following pages list our products and systems available to protect the entire footprint of the building at the most economical stage when the oversite level is reached.

4 Sump provision under the building In this example, the membrane is shown under the oversite slab, rather than above it. Whichever option is selected to suit the construction in question, the outlet from the reception sump is always linked to the membrane using a service pipe flashing. Both outlet options are illustrated. Vertical stack or up to four horizontal connections are possible. Thus gas evacuation can be to perimeter walls if appropriate, terminating with round converter and Cavibrick. USE Placement of a radon sump within the granular fill under the floor slab can aid radon reduction by reducing the pressure under a building. Sumps used in this manner operate passively, relying on positive and negative pressure to naturally exhaust radon via a connecting pipe(s) that rises and discharges the radon. (Normally above roofline in a manner similar to a soil vent pipe). When used in conjunction with total footprint protection no further measures such as assisting extraction using an integral fan are normally required. Radon Gas reception sump by Cavity Trays of Yeovil Somerset BA22 8HU ( ). Incorporate sump centrally within granular fill in accordance with best practice, to service area not exceeding 250m². Connect extraction pipe. Spur connect additional sumps to service static pockets or sub-floor areas. Number. Radon / Methane gas reception sump DIMENSIONS 510mm x 240mm + 110mm porthole projections x 5 GAS EXIT RATIO 4:1 MAXIMUM SERVICEABLE AREA >250m² MAXIMUM SUMPS PER OUTLET PIPE 5 SUMP TO FAR LIMIT OF ANY AREA Not more than 15 metres OUTLET Via soil /drain 110mm nom pipe MATERIAL Polypropylene SUMP This is because the presence of uninterrupted protection across the building footprint guards wall and floor junctions via which ingress entry can commonly occur. Thus the purpose of the sump is to aid reduction rather than eliminate it. DETERMINING YOUR REQUIREMENTS We recommend advantage is taken of our takeoff service. We will be pleased to calculate your requirements and submit a proposal and scheduled for your consideration. Each sump has four side connections and one top connection. This permits interconnection if a large area involving multiples of sumps is required. DESIGNERS COMMENTS Do not use excessive fines around sump. In sub-floor applications performance is dependent on the water table being below and therefore not adversely affecting exhalation. Note maximum pipe runs and areas serviced by any single or interconnected sump. 134 PHONE FAX enquiries@cavitytrays.co.uk

5 Oversite protection USE Selection can be made from two types of membrane that provide both damp-prevention and radon arrestment qualities. In both instances the radon membrane is applied to the entire oversite and provision is made at all oversite / perimeter wall junctions to integrate with the cavity wall barriers described later. Termed combination membranes because they both offer damp and radon prevention qualities, they differ in the following ways: Footprint Radon Membrane is a loose-laid membrane supplied in wide rolls. It is primarily designed to be installed below or above a ground bearing slab or over the top surface of a suspended floor. It is manufactured from heavy duty reinforced polyethylene and offers good transmittance and permeability prevention qualities. It is conventionally laid dry with all joints lapped and sealed using integrity bonding tape. DETERMINING YOUR REQUIREMENTS We recommend advantage is taken of our takeoff service. We will be pleased to calculate your requirements and submit a proposal and scheduled for your consideration. Radon Gas Oversite Membrane Type. by Cavity Trays of Yeovil Somerset BA22 8HU ( ). Install membrane at appropriate stage in accordance with accompanying instructions observing best practice. Sections show Type N membrane to oversite only and methane/radon cavity barriers within cavity walls, lap jointed to provide continuous integrity. Radon Footprint Membrane DIMENSIONS SUPPLIED IN ROLLS 25m x 2m and 4m WEIGHT 410gm ² THICKNESS 0.4mm TENSILE STRENGTH 750N/50mm TEAR RESISTANCE >400N ELONGATION 15-30% Lap + integrity seal tape MOISTURE VAPOUR TRANSMISSION 0.3gm ² 24hr ¹ WATER VAPOUR RESISTANCE >1024MNsg ¹ RADON TRANSMITTANCE <20x10 9 ms ¹ RADON PERMEABILITY <10x10 12 m²s ¹ The alternative Membrane is Type N Sitesealer Membrane. Sitesealer is supplied in narrower rolls on a carrier paper that upon removal exposes the self-adhesive edge strip. This permits the membrane to be applied to suitably prepared surfaces and adjoining widths to adhere and thus form a continuous presence. Type N Sitesealer Membrane consists of a crossorientated top layer of polyethylene. laminated to a bitumen polymer adhesive base layer. Between these layers is sandwiched a full width aluminium primary integrity sheet. This barrier offers excellent performance with exceedingly low gas permeability. Sitesealer Membrane Type N DIMENSIONS SUPPLIED IN ROLLS 30sq metre rolls: 28.6 x 1.05m WEIGHT 1.2Kg/m² THICKNESS 1.0mm TENSILE STRENGTH 230N PUNCTURE RESISTANCE N 250 (ASTM E154) ELONGATION 50% Lap + integrity seal tape MOISTURE VAPOUR TRANSMISSION <0.1gm ² 24hr ¹ METHANE/RADON PERMEABILITY <0.03ml/m²/day/atmos DESIGNERS COMMENTS Consider to provide protection where methane or radon gas is present within the ground. When the Type N underwent the original radon monitoring tests the diffusion co-efficient was reported as being less than 5 x (10-14m²s-1). Type N has a low permeability of both methane and radon gas. The BBA appraisal confirmed use satisfied the appropriate Building Regulations. Footprint Radon Membrane does not incorporate an aluminium layer but is polythene based. Appropriate where protection is limited to horizontal surfaces and there is no accompanying requirement for adhesion to non-horizontal surfaces. PHONE FAX enquiries@cavitytrays.co.uk 135

6 Protection from oversite & through the cavity walls USE Radon cavity barriers are built in all the exterior cavity walls at ground level around the building. Their function is to arrest radon gas rising in the wall cavity - that would otherwise act as a conduit for gas. Instead gas is prevented from rising and is exhausted out of the cavity wall via cavibricks installed at intervals under the cavity barrier level. The barrier is shaped so any water permeating above and collecting on it is discharged via Caviweeps. Rising gas is arrested and discharged through cavibricks in the external skin. Above the barrier caviweeps discharge penetrating water. Radon Gas cavity barriers by Cavity Trays of Yeovil Somerset BA22 8HU ( ). Incorporate radon cavity barriers at appropriate levels within all exterior walls. Ensure all barrier lengths, steps and corner profiles are lapped and sealed as accompanying instructions. Inboard section of barrier to lap and be sealed with oversite membrane to provide unpunctuated protection. DETERMINING YOUR REQUIREMENTS We recommend advantage is taken of our takeoff service. We will be pleased to calculate your requirements and submit a proposal and scheduled for your consideration. Radon Cavity Barriers DIMENSIONS Profile to suit wall detail Supplied in 2440mm lengths Angles / Steps Preformed to match profile. Std angles 450mm x 450mm Lap and integrity seal strip supplied in 30m rolls Lap + integrity seal tape MATERIAL Petheleyne CTR 1.4 <1.6 RADON PERMEABILITY Less than ¹²m²s ¹ COLOUR Black Importantly barrier presence is uninterrupted and unpunctuated from outside face to oversite where it laps and seals with the oversite membrane. In some applications (pending levels) the radon cavity barriers may act also as a wall DPC. Barrier lengths are manufactured in all profiles to suit the project. Matching profiled angles and preformed drops accommodate changes of level, corners and maintain integrity across openings. Radon Cavity Wall Barrier lengths and angles by Cavity Trays of Yeovil Somerset BA22 8HU ( ). Install radon cavity wall barrier lengths and angles at appropriate stage in accordance with accompanying instructions and schedule observing best practice. Typical examples of angles that can be supplied in any dimensions to suit site and construction requirements. DESIGNERS COMMENTS Without uninterrupted interfacing of oversite membrane with cavity barrier, the protection will be discontinuous at one of the most vulnerable points between floor and wall. Incorporating a cavity barrier that commences at the exterior skin face and projects through and beyond the cavity wall so it can seal with the oversite membrane ensures shielding measures are maximised. See NHBC 4.1- D7 and 5.2-D4. Be aware that areas identified as radon-affected are based on existing property readings and if you are constructing to a different standard you might reasonably expect your new property to perform differently. Consider whether radon gas might accumulate to a greater extent within a property that is constructed to more air-tight standards? 136 PHONE FAX enquiries@cavitytrays.co.uk