Crawl Spaces, Piping and Fans

CRAWL SPACES

Perforated pipe used to collect soil gas laid on floor of crawl space

A length of perforated pipe is laid on top of the soil running the length of the crawl space. The pipe will collect the radon from beneath the plastic sheeting when connected to a fan.

A high density, cross laminated polyethylene sheeting is then laid on the soil. This sheeting is a very strong plastic that will resist tearing.

High density polyethylene laid on dirt with edges and seams sealed

The seams should be overlapped and sealed. The edges should also be sealed to the walls of the crawl space, to insure good collection efficiency and to reduce the potential of the plastic being moved. The use of a durable plastic prolongs the life of the system and also allows for storage in the crawl space.

After the plastic has been installed, a solid PVC pipe is connected to the perforated pipe beneath the plastic. The PVC pipe is then routed to the radon fan.

This kind of mitigation system also helps reduce moisture in the crawl space.

PIPING AND FANS

Key Piping Points

• Pipe Material
• Thickness
• Pipe Rating
• Size

• PVC or ABS
• Schedule 40
• DWV (Cellular Core)
• Four Inch

• Follow manufacturer's recommendations when gluing pipe and fittings
• Slope pipe back to suction point to avoid build up of condensation (1/8” per foot)
• Support pipe every eight feet, vertically and every six inches horizontally
• Label pipe on each level where visible “Radon Deduction System"
• Two 45 degree fittings can be used to offset pipe
• When penetrating fire walls with vent pipe, maintain fire wall rating with fire collars or appropriate fire caulk
• Allow 30” of vertical space for installation of the fan in an attic

Downspout (3” x 4”) is used outside for aesthetic reasons.

Fan Locations

The suction piping is connected to a radon fan that must be located in an unoccupied attic, a garage, or outside the home. These fans are quiet and use about 60 watts of electricity. Because radon is constantly generated in the soil beneath the home, the fans must operate continuously.

 
Discharge should be high to avoid radon entering building. Minimum of 10 feet above grade. 10 feet from any openings 2 feet below discharge. Above eave. 1/4 inch bird screen

The fan discharge is routed up through the roof or up along an outside wall to a high point on the house. It must be pointed upward to force the collected radon up and away from the home. It is very important that the discharge not be near the ground, otherwise, the radon might re-enter the structure and increase the level of radon in the home. Radon concentrations in excess of 2000 pCi/L have been measured in some discharge pipes.

Rain caps interfere with system efficiency and are not needed. However, screens should be placed on the discharge to keep birds and squirrels from entering the pipe.

System Indicators

As part of the installation of a depressurization system, an indicator must be installed which will tell the homeowner if something has changed the performance of the system. This is in addition to retesting the home for radon after the installation and repeating this test at least every two years. Three of these indicators are indicated below.

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