Radon Testing and Mitigation Systems

Crawlspace Membrane – Gaps / Holes

The Radon mitigation system’s crawlspace membrane covering the crawlspace floor had visible gaps and/or holes. The crawlspace membrane must be fully sealed and airtight to allow the Radon mitigation system to draw a vacuum below the membrane to collect and remove the Radon gas emanating up from the soil. Both the AARST and NRPP Radon mitigation system installation standards that regulate system design and installation are very precise and technical for the expressed purpose of preventing the reentrapment of Radon gas back into the home. By modern standards:

The membrane must be sealed at the seams and at the foundation wall. All openings in the membrane must be sealed in a permanent airtight manner.
Seams should be overlapped 12 inches and sealed an appropriate caulk or membrane tape.
The soil membrane must meet ASTM E1745 Class A, B, or C
The membrane should permanently be secured to the foundation wall (do not go all the way up to the rim joist).
Wood used as batten strips should be resistant to moisture and insects.
The connection point to the perforated suction pipe must be below the membrane
Friable Asbestos should be removed or encapsulated prior to installation
Debris on the floor of the crawlspace should be removed prior to installation of membrane
Membrane CAN be on top of preexisting vapor barrier, but perforated pipe must be below both layers

It is recommended that an NRPP certified installer be asked to further evaluate and create an action plan for repairs. A list of local NRPP Radon Professionals can be found here: https://nrpp.info/pro-search/

Perforated Suction Pipe Above Crawlspace Membrane

The Radon mitigation system’s crawlspace perforated suction pipe was incorrectly installed on top of the crawlspace membrane. The crawlspace membrane must be fully sealed and airtight to allow the Radon mitigation system to draw a vacuum below the membrane to collect and remove the Radon gas emanating up from the soil. Both the AARST and NRPP Radon mitigation system installation standards that regulate system design and installation are very precise and technical for the expressed purpose of preventing the reentrapment of Radon gas back into the home. By modern standards:

A new membrane CAN be on top of preexisting vapor barrier, but the Radon collection perforated pipe must be below both layers

Suction Pipe Not Schedule 40 PVC

The Radon mitigation system’s “suction" pipe (negatively pressured) was not constructed using an appropriate material. The pipe that runs from suction point to the fan must be constructed of schedule 40 or thicker PVC material. Both the AARST and NRPP Radon mitigation system installation standards that regulate system design and installation are very precise and technical for the expressed purpose of preventing the reentrapment of Radon gas back into the home.