GB2465751A - Apparatus and method for venting radon gas from under a building - Google Patents

Abstract

The invention relates to the protection of buildings from the ingress of unwanted gases, such as radon. The invention comprises a sump liner 27 which is introduced into an underground cavity or sump 22. The sump liner comprises a generally elongate hollow body 26 which is connected to an extraction pipe 30 leading to a discharge point 34. The hollow body 27 has at least one aperture 46, 47 in its side wall to allow ingress of subterranean gases from the surrounding soil when located within the sump or cavity 22. The sump liner may be manufactured by injection moulded. Later embodiments relate to a system and method for extracting subterranean gases by connecting the sump liner to a fan 32 which is in turn connected to a discharge unit 33. Alternatively the extraction means may be a passive extraction means.

Description

Apparatus for use in protecting buildings The present invention relates generally to apparatus for use in protecting buildings, especially, but not exclusively, from the ingress of subterranean gases.

The realisation that radon gas, a known health hazard, emanates from the ground over large areas of the country, has resulted in an ever more sophisticated attempt to protect buildings from the ingress of such gas in order to protect the occupants from the radiological risks involved in breathing it.

The hazards of radon gas have been recognised for some time and in the most seriously affected regions regulations require the construction of new buildings to conform to certain patterns in order to mitigate its effects. These include the construction, beneath an impermeable barrier associated with a ground floor platform, of an underground sump connected to an extraction pipe having passive or active means for drawing the gaseous content of the sump out from beneath the building and discharging it at a point in the atmosphere where it can dissipate harmlessly without causing an unwanted concentration likely to result in harmful effects on the building's occupants.

In addition, the Building Research Establishment has provided information on remediation of the harmful effects resulting from the presence of radon gas in the ground, largely involving techniques for isolating the interior of the building in order to prevent the ingress of such gas. As far as new buildings are concerned, this can be achieved by providing a pre-formed sump under the floor before it is cast, the sump having openings to allow gas from the ground to permeate into it, and being connected to extraction pipes having active or passive means for withdrawing gas from the interior of the sump and discharging it at a safe location, either remotely from the building, or adjacent to the building but in a location where the prevailing wind and/or the absence of window or door openings will allow it to dissipate into the and/or the absence of window or door openings will allow it to dissipate into the atmosphere, or, alternatively, at a relatively high level in relation to the height of the building, and preferably above the highest point of any openings in the building. As far as existing buildings are concerned, however, it is not easy to install a pre-formed sump in view of the level of excavation required, and one known technique for protecting existing buildings from the ingress of radon gas is to form a so-called "mini" sump closely adjacent one wall under the floor. This can be achieved by penetrating the wall at a lower level than the floor, usually by drilling or boring a hole in the wall in the region of 10-15cm in diameter and then excavating, usually manually, a void in the soil under the floor. The void need only be in the region of half a metre in diameter and, because it is located closely underneath the floor, it is not at risk of collapse of soil to refill it. It is known that, for a typical dwelling, a single sump of this type is likely to have an influence region over an area of approximately of 2502m, or to extend for a distance approximately 15m from the sump (although obstructions below the floor slab may reduce ifs effectiveness) and given the dimensions of the average domestic building this means that it is usually not necessary to install the sump in the middle of the building floor as may be preferred for a new building. A sump located closely adjacent the wall is usually sufficient and, in buildings having greater dimensions, it is possible to provide two such sumps spaced from one another such that their regions of influence overlap.

The production of such a "mini" sump does, however, involve certain difficulties, apart from the time and labour involved in manually removing the soil from the void. These include the risk to the operator who has to introduce an arm through the opening in the wall in order to reach in to the void as it is being formed. The possibility, therefore, exists that some of the material may fall during excavation and trap the operator's hand.

There is also the fact that the reach of an average individual may be insufficient to form a cavity of sufficient size, and further the nature of the material under the floor slab may not lend itself to manual excavation in such inconvenient conditions.

The present invent ion seeks to provide means, a system and a method by which the shortcomings of the previously-known techniques can at least be mitigated, if not entirely overcome, to provide a mini sump which can be produced quickly and easily without placing the operative at risk whilst nevertheless providing with certainty a sump having predetermined dimensions so as to be certain to have an adequate volume for the intended purpose.

According to one aspect of the present invention, therefore, a sump liner for defining an underground cavity or sump comprises a generally elongate hollow body having means at one end for connection to an extraction pipe, and at least one aperture in its side wall to allow the ingress of subterranean gases from the surrounding soil when located within the said sump or cavity.

Preferably, the apertures are spaced along the length of the said hollow body, and in the preferred embodiment of the invention the said elongate hollow body is generally cylindrical. A right-circular cylindrical form is probably the most convenient althouh other generally cylindrical shapes such as elliptical, oval and prismatic (such as triangular or square cross section) may also be employed. The elongate hollow body may be fabricated from elementary members, such, as panels in the case of a flat-sided cylindrical form, or may be a monolithic injection-moulded unit. Further a longer body may be produced by forcing two or more shorter bodies end-to-end.

However it is formed, and whatever the cross sectional shape or length, the said hollow body may be open at an end remote from the said connections means, and closable by an end cap which, itself, may have apertures therein if desired, although this is not essential.

The diameter of such an end cap is preferably greater than that of the said hollow body so that, when the body is introduced into an elongate bore-like cavity an interspace between the outer surface of the body and that of the surrounding bore is produced. To encourage the formation of such an interspace the connection means may themselves a diameter larger than the main part of the hollow body, and this diameter may be comparable to, or exactly the same as, that of the end cap.

The apertures in the side wall of the said hotlow body may comprise at least one aperture of a first size and at least one aperture of a second size smaller than that of the said first size. The aperture or apertures in the side wall of the body may be formed as slits or slots or as guarded or unguarded openings. A guarded opening may be formed, for example, by forming the said at least one aperture (or all of the apertures if there are more than one) in the side wall of the hollow body by means of a depression defining a surface discontinuity. Such surface discontinuity may be linear and preferable extends generally transverse the length of the body. This would, of course, be effectively circumferential in the case of a cylindrical hollow body.

The said coupling means may be in the'form of a male or female coupling element for connection with, respectively, a female or male coupling element carned on or formed by the extraction pipe. This may, for example, take the form of an axial flange or collar.

The hollow body of the sump liner may have an imperforate upper wall section over a part of the circumference thereof intended to be uppermost when installed, whereby to protect it against ingress of soil or other particles from above into the sump thus formed.

Alternatively, there may be provided a guard element extending over part of the hollow body intended to be uppermost when installed, whereby to protect it against the ingress of foreign bodies.

In embodiments in which there are a plurality of apertures in the side wall of the hollow body, it is preferred that at least one aperture is of larger dimensions than the others, with an array of apertures of smaller dimensions surrounding it.

The present invention also comprehends a system for the extraction of subterranean gases from a region below a building, comprising a sump or cavity in the ground below the building and defined by a liner in the form of an elongate hollow body having at least one opening in at least the side wall thereof, the sump liner being connected to a substantially imperforate extraction pipe leading to active or passive extraction means the outlet from which is ducted to a discharge outlet.

Preferably, the extraction pipe passes through a side wall of the building al a level below that of the floor slab. Alternatively, however, the extraction pipe may pass though the floor slab itself into a void formed beneath it.

The system of the present invention may include a pump or fan in communication with the extraction pipe for driving gases drawn from the sump towards the discharge outlet.

The discharge outlet itself may be located at a high level, for example in the vicinity of the eaves of a building, or at low level providing it is not anticipated that discharged gases may re-enter the building. It is also possible to use the mini-surnp and the system of the present invention in a reverse sense from that described above, namely to introduce clean air drawn from the surrounding atmosphere into the mini-sump under a slight superatmospheric pressure.

The present invention also comprehends a method of preventing or inhibiting subterranean gases entering a building from a region below it, comprising the steps of: forming a void of cavity in the soil beneath the floor slab of a building by working through an opening in the side wall of the building or in the floor slab itself; introducing an elongate cavity liner in to the said void or cavity, the said liner have apertures in it side walls and means for connecting one end thereof to an extraction or delivery pipe; connecting the said cavity liner to the said extraction or delivery pipe and creating a sub-atmospheric (or a superatmospheric) pressure within the lined cavity by extracting or introducing gas through the said extraction or deliver pipe by passive on active means whereby to encourage subterranean gases in the soil surrounding the lined cavity to enter it through the said opening in the side wall of the said liner, or to permeate the soil beneath the building with clean air.

The method of the invention may be performed in a number of different ways, although it is preferred that the void or cavity is formed by drilling or boring to form a generally cylindrical elongate hollow space. Ideally, this hollow space is of dimensions only slightly greater than those of the greatest diameter part of the liner (namely the cap and/or the connector).

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional side view through a part of a building having a system according to the invention, incorporating a sump liner in accordance with the invention fitted thereto; Figure 2 is a similar sectional side view of an alternative embodiment in which the sump is fitted more centrally within the interior of the building; Figure 3 is schematic side view of a sump liner formed as an embodiment of the present invention; and Figure 4 is an end view of the end cap of the sump liner illustrated in Figure 3.

Ref ening first to Figure 1 there is shown a sectional side view through a building generally indicated 11 illustrating one twin-leaf side wall 12 having an inner leaf 13 and an outer leaf 14 with a layer of thermal insulation 15 between the two leaves. The wall 12 stands on a footing 16 and the building has a conárete floor slab 17 topped with a screed 18 and overlying an impermeable radon barrier 19 which passes though both the inner leaf 13 and outer leaf 14 of the wall 12. This barrier is separate and distinct from the damp proof course 20 with which the outer leaf 14 is provided.

As is usual in building construction, the footings 16 for the wall 12 lie generally below the ground line 21, whilst the damp proof course 20 and the floor slab 17 are somewhat above the ground line 21.

A sump cavity generally indicated 22 is formed in the subsoil 12 beneath the floor slab 17 by drilling or boring through both the outer leaf 14 and inner leaf 13 of the wall 12 beneath the lowermost point of the impermeable radon barrier 19 which, as can be seen in Figure 1, has a cavity tray formation between the inner and outer leaves 13, 14 of the wall 12. By drilling or boring through the two leaves of the wall 12 there are formed two aligned piercings or apertures 24, 25 which are in axial alignment with the cylindrical cavity 22 formed by the same boring operation. A radon sump or mini-sump 26 is formed by the introduction of a sump liner 27 (see Figure 3) which is connected at one end to a horizontal extraction pipe 28 by a coupling 29. The sump liner 27 is generally cylindrical and has apertures 46, 47 in the side wall thereof, and which will be discussed below more fully in relation to Figure 3. The extraction pipe 28 runs from the mini-sump 26 to the outer surface of the outer leaf 14 of the wall 12 where it is connected to an elbow 30 leading to cranked delivery pipe 31 which is connected to a fan 32 the outlet from which is connected to a discharge pipe 33 leading to a discharge outlet 34 at a high level approximately at the eaves of the building 11. The delivery pipe 31 and discharge pipe 33 are secured to the outer leaf 14 of the building 11 by brackets 35, 36, and in the discharge pipe 33 between the fan 32 and the discharge outlet 34 is a condensation trap 37 the outlet from which is connected to an overflow pipe 38.

By forming the cavity 22 in the same drilling or boring operation as the apertures 24, 25 in the wall 12 it is possible to produce this quickly and economically using a machine which avoids the necessity for manual excavation of the subsoil 23 under the concrete floor slab 17. This operation is thus both quick and safe.

Although not illustrated a guard or protective cover over the upper part of the generally cylindrical sump liner 27 may be provided in order to prevent particles of soil entering the sump through the apertures 46, 47 in the side wall thereof. The openings 24, 25 in the wall 12 are sealed to the pipe 28 by a suitable sealant 40 so that the interspace between the extraction pipe 28 and the openings 24, 25 is completely closed and impervious to the escape of, for example, radon gas.

As explained, if the dimensions of the building are not excessively great then a single sump such as that illustrated in Figure 1 is sufficient, and is likely to have an influence over an area of up to about 2502m or for a distance up to about 1 Sm from the sump.

An edge-located sump such as this is acceptable provided the building is of modest size and of regular shape. If these conditions are not met the sump should be positioned centrally, or more nearly centrally, under the house as is illustrated in Figure 2.

In this embodiment those components which are the same as, or fulfil the same functions as, corresponding components in the embodiment of Figure 1 have been allocated the same reference numerals. Thus, a waIl 12 comprising inner and outer leaves 13, 14 is supported on a footing 16 below the ground line 21. A floor slab 17 overlies the soil 23 above the ground line 21 and is isolated from the ground by a radon barrier 19 which passes through both leaves 13, 14; and a damp proof course 20 is provided to isolate the interior of the building from ground moisture.

In thesystem defined in this embodiment the floor slab 17 and radon barrier 19 are pierced within the building by a vertical bore hole which also penetrates into the soil 23 to form a sump cavity 22. A sump liner 27, which may be in all respects identical to the sump liner in the embodiment of Figure 1, other than the orientation in which it is fitted, is introduced into the sump cavity 22 and connected by a connector element 25 to an extractor pipe 28 which leads to a fan 32. The extraction pipe 28 is secured to an internal wall 41 by brackets 35, and the points at which it passes through the concrete slab 17 and the radon barrier 19 are sealed by appropriate sealing elements 42, 43 to ensure that no radon gas from the sump can enter the interior of the building.

As before, a condensation trap 37 between the delivery outlet of the fan 32 and the discharge pipe 33 leads to a suitably dimensioned overflow pipe 38 which, in this case leads to the gutter 44. The discharge pipe 33 leads to a higher level (not shown in the drawings) adjacent the apex of the roof of the building 11.

As can be seen in Figures 3 and 4, the sump liner 27 comprises a circularly cylindrical body 28, in this case of monolithically injection moulded plastics, having a pattern of apertures in the cylindrical side wall thereof comprising a main or central aperture 46 with an array of smaller apertures 47 on either side thereof and extending around the circumference of the cylindrical hollow body 50. At one end, 47, an axial flange 48 is formed as a female coupling element to receive the end of the extraction pipe 28. At the opposite end, 49, of the hollow body 50, there is fitted an end cap 51 of generally cup shape having a cylindrical skirt 52 and a circular flat end wall 53 pierced with an array of openings 54. The external diameter of the cap 51 matches that of the axial flange 48 and, of course, the internal dimension of the cylindrical skirt matches that of the hollow body 5Oso that it can be fitted tightly onto the end 49.

In alternative embodiments (not shown) the pattern of apertures 46, 47 in the hollow body 50 is interrupted such that a part-circumferential imperforate region is formed, which is intended to be uppermost when the sump liner 27 is fitted in the horizontal orientation as shown in Figure 1. This, of course, is not needed in a sump liner when used in the configuration of Figure 2.

Guarded apertures, for example formed by depressions adjacent circumferential slits in the cylindrical side wall may also be provided. These opening preferably face away from the end cap 51 so that, as the sump liner is introduced into the sump cavity 22 there is no tendency for any of the subsoil to enter the openings, and any radially moving particles will encounter the depressions and not be encouraged to pass through the openings.

The length of the mini sump liner 27 may be chosen to form any desired volume of the sump without it being necessary to increase the diameter of the bore, thereby making ii possible to install sumps of different volume utilising the same equipment. This may be achieved by using one long rnini-sump body or by forcing together several shorter ones.

Although an extraction system has been described herein above it will be appreciated that where a pressurisation system is considered more appropriate, that is where the fan 32 draws air from the atmosphere and delivers it into the pipe leading to the sump 27, no alternative structural configuration is required in order to achieve this apart from the obvious reverse orientation of the fan.

Likewise, although positively ventilated systems incorporating a pump or fan have been described it will be understood that the invention is equally applicable to systems in which so-call passive" ventilation is achieved by a suitable configuration of pipe work without requiring a positive displacement of air such as by fan or pump.

Claims (28)

1. CLAIMS1. A sump liner for defining an underground cavity or sump, comprising a generally elongate hollow body having means at one end for connection to an extraction pipe and at least one aperture in its side wall to allow ingress of subterranean gases from the surrounding soil when located within said sump or cavity.
2. 2. A sump liner as claimed in Claim L in which the apertures are spaced along the length of the said body.
3. 3. A sump liner as claimed in Claim 1 or Claim 2, in which the said elongate hollow body is generally cylindrical.
4. 4. A sump liner as claimed in Claim 3, in which the said elongate hollow body is a right circular cylindrical form.
5. 5. A sump liner as claimed in any preceding claim, in which the said hollow body is a monolithic injection-moulded unit.
6. 6. A sump liner as claimed in any of Claims 1 to 4, in which the said hollow body is formed from a plurality of shorter bodies joined end-to-end.
7. 7. A sump liner as claimed in any preceding claim, in which the said hollow body is open at an end remote from the said connection means, and closable by an end cap.
8. 8. A sump liner as claimed in Claim 7, in which the end cap itself has apertures therein.
9. 9. A sump liner as claimed in Claim 7 or Claim 8, in which the diameter of the said end cap is greater than that of the said hollow body, whereby to create an interspace around the said body when it is introduced into the said void or cavity from one end with its cap end leading.
10. 10. A sump liner as claimed in any of Claim 7 to 9, in which the said connection means at the said one end of the hollow body has a diameter greater than that of the said hollow body, and approximately the same as that of the said end cap.
11. 11. A sump liner as claimed in any of Claims to 10, in which the apertures on the side wall of the said hollow body comprise at least one aperture of a first size and at least one aperture of a second size smaller that of the said first size.
12. 12. A sump liner as claimed in any preceding claim, in which the aperture or apertures in the side wall of the body are formed as slits or slots or as guarded openings.
13. 13. A sump liner as claimed in any preceding claim, in which the said coupling means is in the form of a male or female coupling element for connection with respectively a female or male coupling element carried on or formed by the extraction pipe.
14. 14. A sump liner as claimed in any preceding claim, having an imperforate upper wall section over a part of the hollow body intended to be uppermost when installed, whereby to protect it against ingress of soil or other particles from above into the interior of the sump thus formed.
15. 15. Asump liner as claimed in any preceding claim, in which there is further provided a guard element over part of the hollow body intended to be uppermost when installed, whereby to protect against the ingress of foreign bodies.
16. 16. A sump liner as claimed in any preceding claim, in which the said at least one aperture in the side wall of the hollow body is formed by a depression defining a surface discontinuity.
17. 17. A sump liner as claimed in Claim 16, in which the said surface discontinuity is linear and extends generally transverse (or circumferential in the case of a cylindrical hollow body) the length of the hollow body.
18. 18. A sump liner as claimed in any preceding claim, in which there are a plurality of apertures in the side wall of the hollow body, with at least one larger hole surrounded by an array of smaller apertures.
19. 19. A system for the extraction of subterranean gases from a region below a building, comprising a sump or cavity in the ground below the building defined by a liner in the form of an elongate hollow body having openings in at least the side wall thereof, connected to an imperforate extraction pipe leading to active or passive extraction means the outlet from which is ducted to a discharge outlet.
20. 20. A system as claimed in Claim 19, in which the extraction pipe passes through a side wall of the building at a level below that of the floor slab.
21. 21. A system as claimed in Claim 19 in which the extraction pipe passes through a floor slab into a void formed beneath it.
22. 22. A system as claimed in any of Claims 19 to 21, in which the discharge outlet is located at a level in the region of the upper part of the building.
23. 23. A system as claimed in Claim 19, in which the said liner is as defined in any of Claims ito 18.
24. 24. A method of preventing or inhibiting subterranean gases entering a building from a region below it, comprising the steps of: -forming a void or cavity in the soil beneath a floor slab of the building by working through an opening in a side wall of the building or in the floor slab itself; -introducing an elongate cavity liner info the said void or cavity, the said liner having apertures in ifs side wall and means for connecting one end to an extraction or delivery pipe; -connecting the said cavity liner to the said extraction or delivery pipe, and -connecting a sub-atmospheric or superatmospheric pressure within the lined 25. cavity by respectively extracting or introducing gas through the said extraction or delivery pipe by passive or active means whereby to encourage subterranean gases in the soil surrounding the lined cavity to enter it through the said openings in the side wall of the said liner, or respectively to permeate the soil beneath the building with air drawn from the surrounding atmosphere.
25. 25. A method as claimed in Claim 24, in which the void or cavity is formed by drilling or boring to form a generally cylindrical elongate hollow space.
26. 26. A method of extracting subterranean gases substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
27. 27. A system for extracting subterranean gases from beneath a building, substantially as hereinbéfore described with reference to, and as shown in, the accompanying drawings.
28. 28. A sump liner substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.