Currently the Government is reviewing Part C of the Building Regulations. In particular the way in which measures should be taken to protect buildings (and thus their inhabitants) from the effects of radon gas. Radon is an invisible gas that permeates from the ground. Placing a building on radon emitting ground can result in the gas accumulating within the building. With buildings becoming more airtight, there is accompanying concern that radon might accumulate within rooms to an unacceptable concentration. Radon is recognised to cause lung cancer and according to Government figures, each year this results in an estimated 2000 avoidable deaths.
The Building Regulation review currently taking place follows announcements from the World Health Organization (WHO) that radon is more dangerous than first realised and there is no safe level. Professor William Angell, Chair of the WHO International Radon Project, stated it is the responsibility of those who put the building on the land to ensure it is not radon affected.
Radon is measured in Becquerels per cubic metre and the current UK regulations state there is no need to take any radon prevention measures if the reading in a domestic property is under 200 Becquerels – that’s the level considered safe in the UK. Or to be more accurate it used to be considered safe, but two years ago (following the WHO announcement) the Governments Health Protection Agency (HPA) announced that while the Building Regulation Action Level in the UK for dwellings should remain at 200 Becquerels, a new Target Level of 100 Becquerels was recommended as it was a safer level. Thus designers and builders of dwellings have two standards from which to choose. It prompts the question of to what extent is the safer level is being targeted and whether house purchasers are being given the choice?
While dwellings currently have an Action and a Target Level, commercial buildings are treated differently. Commercial buildings have an Action Level of 400 Becquerels – double that of dwellings. It is thought less time should be spent within a commercial building compared with a home. This logic is confusing as a large number of buildings within which occupants spend a far greater time fall within the commercial category. (Consider boarding schools, care establishments, etc).
Two of the primary radon access routes into a typical building are where floors and external walls meet and via the cavity from which it can permeate wherever an opportunity exists (be it around openings, via cracks, via the roof space etc). With the negative air pressure within a typical dwelling compared with under it, radon gas can be drawn inwardly.
One can take partial steps to reduce radon by incorporating a sump under the property to reduce pressure and duct off the radon, but its effectiveness as with any radon prevention measures can only really be determined after the property has been completed and a reading is taken. If the reading is unacceptable, the expense of regularising an existing building can be extensive.
Fortunately the remedy is simple. One can protect the entire footprint of the building so radon is prevented from entering via the usual routes.
Commonly the oversite membrane terminates against the inner skin of the cavity wall and the DPC’s in both inner and outer skins are separate. These three protective mediums function to prevent damp movement, but in isolation fail to address contaminated land gases.
The revision of Part C will hopefully introduce a more disciplined approach to protecting new properties.
Entire footprint protection is an assured way forward but it is suspected the new regulations might take a compromised route, and instead designers and builders will be directed to continue using the radon maps to determine whether they should incorporate safety measures because the property to be built is within a known radon affected area. As these maps do not indicate the ground condition but simply whether there are existing tested properties in an area that have elevated readings, this approach is flawed. It assumes a new airtight property built to the new standards will behave (and therefore have the same readings as) the existing tested property that may be extremely old, draughty and contain numerous natural dissipation routes (chimneys for instance). If your new property construction does not exactly match the existing property, you cannot expect a similar reading. One can only hope the revision of Part C will include a positive reduction in the Radon Action Level and eliminate the current dual standards?
The HPA issues radon testing monitors should anyone wish to determine the status of your own home and they are available upon request. Meanwhile, until the new regulations are known, designers, builders and clients might wish to focus on which level their projects are currently being constructed - the Action Level or the safer Target Level? In terms of duty of care, the health of the inhabitants, and the ongoing desirability/asset value of a property built to a safer standard, many consider this a question to which there is only one real answer?
About the author
John Shillabeer is Chairman of family-owned Cavity Trays Ltd, the longest-established company in its specialised field. The company designs and manufactures specialist construction products to protect the building envelope and is the only such company awarded European Technical Approval.
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