Title:
Apparatuses, Systems and Methods for Pre-Configuring New Structure Foundations For Soil Gas Mitigation Systems
Kind Code:
A1


Abstract:
A method for pre-configuring a foundation of a new structure, includes providing an apparatus that has a base end and an opposing end, the apparatus arranged such that the perimeter of the base end is longer than the perimeter of the opposing end, placing the apparatus on the base end at a desired location within the perimeter of a frame arranged to confine pre-cured concrete and applying pre-cured concrete within the frame. A system for preventing the migration of soil gas into a structure includes a soil gas barrier, a layer of permeable material and an apparatus. The apparatus is in contact with the soil gas barrier and has a base end with a first port forming a first area and an opposing end with an output port having a second area that is smaller than the first area.



Inventors:
Howell, Terry E. (Smyrna, GA, US)
Application Number:
11/781486
Publication Date:
01/29/2009
Filing Date:
07/23/2007
Primary Class:
Other Classes:
405/257
International Classes:
E02D7/00
View Patent Images:
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Primary Examiner:
LAGMAN, FREDERICK LYNDON
Attorney, Agent or Firm:
SMITH TEMPEL BLAHA LLC (Atlanta, GA, US)
Claims:
What is claimed is:

1. A method for pre-configuring a foundation of a new structure, comprising: providing an apparatus that has a base end and an opposing end, the apparatus arranged such that the perimeter of the base end is longer than the perimeter of the opposing end; placing the apparatus on the base end at a desired location within a frame arranged to confine pre-cured concrete; and applying pre-cured concrete within the frame.

2. The method of claim 1, wherein providing an apparatus comprises sealing an output port in the opposing end.

3. The method of claim 2, wherein sealing the output port comprises using an insert.

4. The method of claim 2, wherein sealing the output port comprises engaging threads.

5. The method of claim 1, wherein providing an apparatus comprises forming an opening along a side between the base and opposing ends.

6. The method of claim 5, wherein providing an apparatus comprises arranging the output port to permit the passing of a forearm and upper arm of a technician.

7. The method of claim 6, wherein providing an apparatus comprises arranging the opening along a side between the base and opposing ends to permit the passing of the forearm of the technician.

8. The method of claim 5, wherein providing an apparatus comprises forming a second opening along a side between the base and opposing ends.

9. The method of claim 1, wherein providing an apparatus comprises arranging the apparatus such that the apparatus can be stackably arranged within a portion of the volume partially enclosed by a second apparatus arranged like the first apparatus.

10. An apparatus, comprising: a base end forming a first port, the first port defining a first area; an opposing end forming an output port, the output port defining a second area that is smaller than the first area, the opposing end configured to engage a cap, the cap and opposing end configured to prevent the passage of an item through the output port into the volume between the base and opposing ends.

11. The apparatus of claim 10, further comprising a side forming a first input port, the side arranged between the base and opposing ends.

12. The apparatus of claim 11, wherein the output port is arranged to permit the passing of a forearm and upper arm of a technician.

13. The apparatus of claim 12, wherein the first input port is arranged to permit the passing of the forearm of the technician.

14. The apparatus of claim 10, wherein the opposing end comprises threads to engage the cap.

15. The apparatus of claim 14, wherein the cap is configured to receive a pipe.

16. The apparatus of claim 10, wherein the base end comprises a lip.

17. A system for preventing the migration of soil gas into a structure, comprising: a soil gas barrier arranged between the underside of a concrete foundation slab and a layer of permeable material, the layer of permeable material resting on compact soil; and an apparatus in contact with the soil gas barrier, the apparatus comprising: a base end supported by the compact soil, the base end forming a first port, the first port having a first area; an opposing end forming an output port, the opposing end extending to the upper surface of the concrete foundation slab and exposed to the interior volume of the structure, the output port having a second area that is smaller than the first area.

18. The system of claim 17, wherein the soil gas barrier is fixed to the apparatus.

19. The system of claim 17, wherein the apparatus further comprises an input port formed in a side between the base and opposing ends, the input port arranged below the underside of the concrete foundation.

20. The system of claim 19, wherein the output port permits the passing of a forearm and upper arm of a technician and wherein the input port permits the passing of a forearm of the technician to the layer of permeable material.

Description:

BACKGROUND

The present apparatuses, systems and methods relate to the pre-configuration of new construction foundations to transport and dissipate soil gases emitted from the ground proximate a structure's foundation in a safe and effective manner.

Conventional dwellings and other building structures constructed with a basement are typically built upon foundation walls which define the basement area. The foundation walls, footers and basement slab are often in direct contact with the ground or a vapor barrier surrounding the structure. Other conventional structures constructed without a basement have footers and a slab with no foundation walls. Both types of structures are susceptible to the migration of soil gasses through gaps in the vapor barrier and cracks or gaps in the foundation walls and slabs or by concentration gradient diffusion.

Radon is an invisible, odorless, tasteless radioactive gas produced by the natural decay of uranium in the soil. The center for disease control (CDC) in Atlanta, Ga. has reported that human exposure to radon gas is the leading cause of lung cancer among non-smokers. Such human exposure routinely occurs from radon gas that seeps from the ground into dwellings and other structures. Radon and other soil gases migrate between cracks in foundation walls and slabs when a negative pressure gradient between the exterior and the interior of the structure exists. The pressure differential may be generated by mechanical equipment, thermal stack effect, or Bernoulli effect. Scientists estimate that more than 21,000 Americans die annually as a result of radon exposure in their homes.

In a study completed by the Environmental Protection Agency (EPA) in 1988 across a seven state area, it was found that one home in three had dangerous levels of radon gas. The EPA has set a recommended level for remedial action at 4 picocuries per liter of air, which is equivalent to the radiation exposure one would receive from 200 chest x-rays per year. A curie is a unit of radioactivity, equal to the amount of a radioactive isotope that decays at the rate of 3.7×1010 disintegrations per second. Even at 4 picocuries per liter of air, studies have indicated that almost 5 persons out of 100 exposed to these levels of radon will die of radon-induced lung cancer.

A number of conventional systems and methods have been developed to reduce the levels of radon and other soil gases that migrate into dwellings and other structures. Several conventional systems and methods require the excavation and placement of subterranean piping systems adjacent portions of the perimeter of the structure. The placement of these perimeter piping systems is expensive and care must be taken when excavating and or inserting pipe runs in the vicinity of buried gas, water and electric supply lines as well as sewer lines coupled to the structure.

Other conventional systems require the drilling or opening of a hole through the slab and any reinforcing wire mesh or reinforcement bars therein to permit a pipe to be placed in the soil underneath the slab. The placement of these sub-slab pipes through cured concrete is expensive, requires special drill bits and heavy duty drill motors or difficult to control jackhammers to break the slab. Drill bits often encounter portions of wire mesh or reinforcement bar in the slab, which quickly dulls and or ruins the bit. Whether the slab opening is created with a drill or a jackhammer, the task of creating the opening in the slab is noisy and generates a significant amount of dust. After the hole has been made large enough to receive the pipe, a worker excavates the gravel and compacted soil to the desired depth. Once the pipe end is placed in the slab opening, the gap between the slab and the exterior of the pipe must be resealed to prevent the migration of soil gasses around the exterior of the pipe.

EPA publication 402-K-01-002 published April 2001, entitled “Building Radon Out—A Step-by-Step Guide On How To Build Radon-Resistant Homes,” illustrates and describes a number of below slab and above grade (e.g., in a crawlspace) systems that include a “T” or elbow fitting. Two ports of the “T” fitting are inlets for receiving soil gas. A single port of an elbow fitting can receive soil gas. The remaining port of each of the fittings is available for coupling a ventilation stack or outlet to the respective fitting. The publication recommends 3-inch or 4-inch schedule 40 acrylonitrile-butadiene-styrene (ABS) or polyvinyl chloride (PVC) pipe and fittings. Soil gas flow can become constricted if soil and gravel enter the fitting and outlet pipe in below slab installations. As a result, the publication further recommends that a minimum length of 10 feet of perforated pipe be connected to the fitting and placed in the gravel for below slab installations. However, use of a 3-inch or 4-inch pipe fitting alone, or with the recommended length of perforated pipe creates a system that cannot be accessed by a technician to verify that a later completed network of pipe (i.e., after the slab has cured) will permit the required gas flow to reduce pressure in and around the soil below the slab.

Still other conventional systems take advantage of the presence of a sump pit. These dual systems are responsible for the removal of both sub-slab gasses as well as groundwater that may rise to undesired levels under the slab. Accordingly, these systems include multiple seals to prevent the migration of soil gases into the interior of the structure.

Accordingly, it would be desirable to develop economical and effective apparatuses, systems and methods that overcome these shortcomings.

SUMMARY

Apparatuses, systems and methods for pre-configuring new structure foundations for later installed soil gas mitigation systems are invented and disclosed.

More specifically, the subject apparatuses, systems and methods are adapted to enable the installation of soil mitigation systems that prevent the migration of radon and other soil gases into the building structure through cracks, crevices and openings in the structure foundation and/or slab by depressurizing the soil beneath the structure. Another benefit of soil gas mitigation systems is that these systems reduce the amount of moisture present in the soil and soil gases in the proximity of a structure's foundation.

An embodiment of an apparatus comprises a base end and an opposing end. The base end has a first port defining a first area. The opposing end has an output port defining a second area. The second area is smaller than the first area. The opposing end is configured to engage a cap. The cap prevents the passage of an item through the output port into the volume between the base and opposing ends.

An embodiment of a system for preventing the migration of soil gas into a structure comprises a soil gas barrier and an apparatus. The soil gas barrier is placed on a layer of gravel or bare soil and below the underside of a concrete foundation slab. The soil gas barrier is in contact with the apparatus. The apparatus has a base end and an opposing end. The base end is larger in area than the opposing end. The opposing end forms an output port and extends to the upper surface of the concrete foundation slab.

One embodiment of a method for pre-configuring a foundation of a new structure includes the steps of providing an apparatus that has a base end and an opposing end, the apparatus arranged such that the perimeter of the base end is longer than the perimeter of the opposing end, placing the apparatus on the base end at a desired location within a frame arranged to confine pre-cured concrete and applying pre-cured concrete within the frame.

Other devices, methods, features and advantages will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional devices, methods, features and advantages are defined and protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatuses, systems and methods for pre-configuring new structure foundations for soil gas mitigation systems, as defined in the claims, can be better understood with reference to the following drawings. The components within the drawings are not necessarily to scale relative to each other; emphasis instead is placed upon clearly illustrating the elements, features and principles involved in pre-configuring foundation slabs.

FIG. 1 is a schematic diagram of an embodiment of an apparatus for pre-configuring a foundation slab for a soil gas mitigation system.

FIG. 2 is a schematic diagram illustrating a top view of the apparatus of FIG.

FIG. 3 is a schematic diagram illustrating a bottom view of the apparatus of FIG. 1.

FIG. 4 is a schematic diagram illustrating how a technician can access the underside of a foundation via the apparatus of FIG. 1.

FIG. 5 is a functional block diagram of an embodiment of a soil gas mediation system.

FIG. 6 is a flow diagram illustrating an embodiment of a method for pre-configuring a foundation of a new structure.

FIG. 7 is a flow diagram illustrating an embodiment of a method for pre-configuring a foundation slab to enable the installation of a soil gas mediation system.

FIG. 8 is a flow diagram illustrating an embodiment of a method for completing and activating a soil gas mediation system.

DETAILED DESCRIPTION

Apparatuses, systems and methods for pre-configuring new structure foundations for soil gas mitigation systems are disclosed. As described above, improved apparatuses, systems and methods for constructing new structure foundations are presented.

An embodiment of a rough-in box for soil gas mitigation systems provides an optimized interface that traverses a structure's foundation slab. The rough-in box is well suited for later installed active soil depressurization or soil pressurization systems; either active or passive.

In contrast with conventional new construction methods that place a fitting (e.g., a 3″ PVC elbow, “T”, or flange) in the gravel bed prior to concrete application and finishing, the present rough-in boxes provide a significant increase in soil contact area. The increase in soil contact area enables a future soil gas mitigation system to develop a larger (in area) pressure field under a structure's foundation slab. In further contrast with conventional fittings, which include abrupt transitions and turns, the shape of the interior chambers, arrangements and relative sizes of the inlet and outlet ports of the present rough-in boxes, reduce the amount of friction loss encountered in a later installed soil gas mitigation system.

Also in contrast with conventional fittings, which are inherently unstable and easily dislodged during the application and finishing of a concrete foundation slab, the present rough-in boxes include a base end that is larger than an opposing end to increase stability. The opposing or outlet end is initially closed by an adapter and an insert or cap. When placed in accordance with preferred installation techniques, the opposing or outlet end is flush with or extends just above the upper surface of the foundation slab. In some embodiments, the base end is configured with a lip or edge that can be used to engage a stake to fix the rough-in box to the supporting soil at a desired location in the foundation frame. Accordingly, the present rough-in boxes are less likely to become dislodged or fouled with concrete during the application and finishing of the foundation slab.

Moreover, the present rough-in boxes are configured with an outlet port (when the cap or insert is removed) and one or more inlet ports that enable a technician to examine the interior volume to ensure that the box is not fouled with concrete, gravel or other debris. Specifically, the outlet port is large enough to receive the forearm and upper arm of an examining technician. Each of the inlet ports is large enough to receive and enable the hand and a portion of the examining technician's forearm to pass through the inlet. Thus, an examining technician can verify that the soil and gravel (or other gas permeable materials such as a granular drainage pad, sand, geotextile drainage matting, etc.) were installed correctly and that soil, debris or other items are not blocking the input ports of the rough-in apparatus. When necessary, an examining technician can possibly correct the condition before installing a piping system to vent the soil gas outside of the structure. It should be understood that the piping system can be completed in conjunction with the initial construction of the structure or any time thereafter if soil gas concentrations exceed a desired level.

Having generally described the present rough-in boxes, systems and methods for pre-configuring new structure foundations for soil gas mitigation systems, various additional embodiments will be described with respect to FIGS. 1-7. FIG. 1 is a schematic diagram of an embodiment of a rough-in box (i.e., an apparatus) for pre-configuring a foundation slab for a soil gas mitigation system. Apparatus 100 is shown resting upon compact soil. In the illustrated embodiment, apparatus 100 is generally round in shape with a hollow interior. Apparatus 100 has a base end 130, side 120 and an opposing end 110. In the front plan view of FIG. 1, base end 130 is wider than opposing end 110. This arrangement permits multiple instances of similarly arranged rough-in boxes to be stackably arranged to conserve space for storage and shipping.

The length of the perimeter of base end 130 is longer than the perimeter of opposing end 110. Base end 130 is open to the soil below forming a first port 135. First port 135 defines a first area. Opposing end 110 forms an output port 115. The output port 115 defines a second area that is smaller than the first area. Adapter 112 (shown slightly removed from the output port) is arranged to fit within the output port 115. Adapter 112 receives cap 114. The combination of adapter 112 and cap 114 seals the output port 115 of the apparatus 100. Cap 114 can be arranged with threads configured to engage mating surfaces in the hole formed within adapter 112. Alternatively, cap 114 can be arranged with mating surfaces to engage threads formed on the inward facing surfaces of adapter 112. Embodiments that use threads and mating surfaces may also include one or more O-rings (not shown) placed between the horizontal flanges of adapter 112 and cap 114. The O-rings compress to provide a barrier that prevents soil gas or air from traversing the output port. The barrier also prevents concrete and other debris from falling into the interior of apparatus 100.

In other alternate embodiments, adapter 112 receives cap 114 in a press fit arrangement. The press fit can be accompanied by various flexible caulks or adhesives applied to the opposing horizontal flanges of adapter 112 and/or cap 114 to form an air/soil gas tight seal.

Surface 134 is in contact with the compact soil and supports apparatus 100. Lip 132 and surface 136 provide an annular mount for engaging one or more spikes or anchors (not shown) that can be driven into the soil to set apparatus 100 at a fixed position.

Side 120 includes input port 122, input port 124 and input port 126. An additional input port (not shown) opposes input port 124. Each of input port 122, input port 124 and input port 126 are arranged such that the gap formed in side 120 is below the average minimum depth of gravel 150 applied on top of the soil. The combination of first port 135, input port 122, input port 124, input port 126 and any additional ports dramatically increase the soil/gravel contact area over the contact area provided by conventional fittings. Although shown in illustrated embodiments as having a general circular shape of equal size, input port 122, input port 124 and input port 126 are not so limited and can be arranged in different shapes of equal or unequal size as may be desired.

Although adapter 112 and cap 114 are illustrated in an exploded view, it should be understood that when adapter 112 and cap 114 are installed the upper surface of cap 114 matches or slightly exceeds the height of foundation frame 160. As will be explained in greater detail below, when reinforcement rods or wire mesh and concrete are applied within foundation frame 160, apparatus 100 provides an access port through the cured slab to the gravel 150 and soil in an area proximal to each of first port 135, input port 122, input port 124, input port 126 and any additional input ports.

FIG. 2 is a schematic diagram illustrating a top view of the apparatus 100 of FIG. 1 with cap 114 set in adapter 112. The dashed line located proximal to the center of apparatus 100 is representative of output port 115 (FIG. 1) and the lower portion of cap 114 that extends into the port. Side 120 extends from the opposing end to the base end of apparatus 100. Side 120 includes input port 122, input port 124, input port 126 and input port 128 arranged approximately 90 degrees from each inputs port's respective nearest neighbors. It should be understood that more or less input ports can be arranged around the perimeter of the apparatus 100. In the present arrangement of the base end 130 and the opposing end 110 (FIG. 1), additional input ports can be positioned along side 120 such that nearest neighbor ports are separated by less than 90 degrees In other embodiments, when for example, the footprint of apparatus 100 is elongated or has opposing sides that are parallel to one another, one or more opposing sides may each form a respective input port or ports that are arranged below the average minimum depth of the gravel below the foundation slab.

FIG. 3 is a schematic diagram illustrating a bottom view of the apparatus 100 of FIG. 1 looking from first port 135 toward output port 115. The hole in the center portion of annular adapter 112 defines output port 115. Surface 300 (on the internal surface of apparatus 100 extends from the opposing end 110 to the base end 130 of apparatus 100. Surface 300 includes input port 122, input port 124, input port 126 and input port 128 arranged approximately 90 degrees from each input port's respective nearest neighbors. It should be understood that more or less input ports can be arranged around the perimeter of the apparatus 100. In the present arrangement of the base end 130 and the opposing end 110 (FIG. 1), additional input ports can be positioned along surface 300 such that nearest neighbor ports are separated by less than 90 degrees. Surface 134 extends around the perimeter of base end 130 and provides support when apparatus 100 is placed in foundation frame 160 (FIG. 1).

FIG. 4 is a schematic diagram illustrating how a technician can access the underside of a foundation slab 420 via the apparatus 100 of FIG. 1. As shown in FIG. 4, a technician that has removed cap 114 and/or the combination of cap 114 and adapter 112 from the output port 115 can extend both forearm 410 and upper arm 400 through output port 115. In addition, the technician can access gravel layer 150 by extending their hand and forearm 410 through an input port such as input port 122. Thus, a technician can check and verify that concrete, gravel or other debris have not fouled the interior of apparatus 100 and the input ports before installing a piping system to output port 115.

FIG. 5 is a functional block diagram of an embodiment of a soil gas mediation system 500. Soil gas mediation system 500 includes apparatus 100, soil gas barrier 502 and piping system 504. As indicated in FIG. 5, soil gas barrier 502 lies above the gravel 150 and below the cured foundation slab 420. In addition, soil gas barrier 502 surrounds those portions of apparatus 100 that are proximal to gravel 150 and soil. Soil gas barrier 502 can be formed from one or more layers of plastic sheets. Bulk plastic may be unrolled and unfolded and overlapping portions fixed to one another with a suitable sealant or adhesive to prevent the migration of soil gas or air across soil gas barrier 502. Before a technician inserts pipe section 510 into output port 115 and seals the external surface of pipe section 510 to adapter 112, the technician can cut, puncture or otherwise remove soil gas barrier 502 from the areas proximal to input port(s) (not shown). In addition, the technician can cut, puncture or otherwise remove any desired portion of soil gas barrier 502 under first port 135. Optional stakes 505 engage lip 132 to fix the location of apparatus before the foundation slab 420 cures.

Piping system 504 includes pipe sections, straps, couplers, etc. above the upper surface of foundation slab 420. In the illustrated embodiment, piping system 504 includes pipe section 510, pipe section 520, pipe section 540 and pipe section 560 among other items including coupler 552, coupler 554 and fan 550. A first end of pipe section 510 is coupled and sealed to apparatus 100. An opposing end is coupled to a first end of pipe section 520 via a coupler (not shown). Pipe section 520 is supported via strap 532 to horizontal rafter 530 in the inhabitable space above foundation slab 420. A second end of pipe section 520 is coupled to a first end of pipe section 540 via a coupler (not shown). A second end of pipe section 540 is connected via flexible coupler 552 to an input port of fan 550, which is located in an attic or other uninhabited space within the structure above foundation slab 420. An output port of fan 550 is coupled to a first end of pipe section 560 via flexible coupler 554. Fan 550 is arranged to draw air and soil gas from the gravel 150 below the soil gas barrier 502 under foundation slab 420 to develop a negative pressure field below foundation slab 420. Consequently, any gaps or cracks in soil gas barrier 502 and foundation slab 420 will result in air from the interior of the structure being drawn under the foundation slab 420. As a result, soil gas will not traverse the soil gas barrier 502 and foundation slab 420 and enter the structure. Fan 550 may be coupled to controllers and sensors that enable both automatic and manual operation of the fan and provide status information regarding the system to a monitoring station and/or those present in the habited spaces of the structure.

As further illustrated in FIG. 5, pipe section 560 traverses the roof 575 with a second end of pipe section 560 being open to the space external to the structure. Mount 574 supports pipe section 560 to rafter 572. Flashing 570 forms a waterproof barrier in the area proximal to where pipe section 560 traverses roof 575. Rain cap 580 is coupled to the second end of pipe section 560 to prevent precipitation, debris or animals from entering the piping system 504.

FIG. 6 is a flow diagram illustrating an embodiment of a method for pre-configuring a foundation of a new structure. Method 600 begins with block 602 where an apparatus that has a base end and an opposing end is provided. The apparatus is arranged such that the perimeter of the base end is longer than the perimeter of the opposing end. Next, as indicated in block 604, the apparatus is set on the base end at a desired location within the perimeter of a frame arranged to confine pre-cured concrete. Thereafter, as indicated in block 606, pre-cured concrete is applied within the frame.

FIG. 7 is a flow diagram illustrating an embodiment of a method 700 for pre-configuring a foundation slab to enable the installation of a soil gas mediation system. Method 700 begins with block 702 where an apparatus is provided. The apparatus has a base end that is larger than an opposing end. The apparatus is configured with one or more input ports disposed along the side of the apparatus proximal to the base end. Next, as indicated in block 704, the grade is adjusted as required such that when the apparatus is placed upon the soil the opposing end will be in desired alignment with the upper surface of the foundation slab. Thereafter, as indicated in block 706, gravel is added to a frame to a minimum desired average depth across the grade within the frame. In block 708, a soil gas barrier layer is placed above the gravel and is fixed to the outer surface of the apparatus to prevent the intrusion of gravel and concrete into the interior of the apparatus. Next, in block 710, reinforcing material (e.g. reinforcement rods or metal mesh) and concrete are installed above the soil gas barrier.

FIG. 8 is a flow diagram illustrating an embodiment of a method 800 for connecting and activating a soil gas mediation system. Method 800 begins with block 802 where a cap is removed from the pre-installed apparatus. In block 804, the interior of the apparatus is checked to ensure the interior is devoid of concrete and gravel. The interior of the apparatus can be accessed by inserting one's arm through the output port. In block 806, the technician cuts or otherwise removes the soil gas barrier from the area around the input port(s). In block 808, the technician inserts a pipe into the output port of the apparatus and seals any gap between the pipe and the output port. In block 810, the pipe is coupled to one or more additional pipes through the interior and roof of the structure. Preferably, pipes that traverse the interior of the structure are located in an interior wall, closet or mechanical room.

In optional embodiments, a fan is installed in-line with the vent pipe in a non-living space (e.g., an attic), as shown in block 812. The fan has an air/soil gas movement capacity that is sufficient to create and maintain a pressure field beneath the soil gas barrier. A negative pressure field is created by a fan that draws soil gases from under the foundation slab to an exit outside the structure so that the soil gases are mixed with air outside the structure. With a negative pressure field, the pressure under the foundation slab is lower than the pressure above the soil gas barrier. A positive pressure field is created by a fan that draws outside air through the structure so that the outside air exits under the foundation slab. With a positive pressure field, the pressure under the foundation is higher than the pressure above the soil gas barrier. There are circumstances where it may be desirable to create a positive pressure field beneath the foundation slab and soil gas barrier. To reduce noise, the fan is coupled to schedule 40 pipe sections with flexible couplers. In block 814, roof flashing is added to that portion of pipe that extends above the roof line. In block 816, a rain cap is added to the exposed end of the pipe that traverses the roof. Upon completion of the installation, system performance should be evaluated by checking radon levels within the interior of the structure, as shown in block 818. If a desired level of soil gas exposure is not achieved in the habited portions of the structure, all seals (and fan operation for active mitigation systems) should be checked and the system re-evaluated as required until a desired exposure level is achieved or exceeded.

The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Modifications or variations are possible in light of the above teachings. The embodiments discussed, however, were chosen and described to enable one of ordinary skill to utilize various embodiments of the present systems and methods. All such modifications and variations are within the scope of the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.