RRNC 2020 Companion Guidance Section A: Update Comparison CG 1 Companion Guidance Section A Technical Advisories (Compared To Other Guidance And Codes) Requirements (pipe size) Advisory: While 3 inch pipe will usually have capacity to transport an adequate volume of soil gas for foundations up to 2500 sq. ft., 4 inch pipe is often needed for larger foundations that are up to 4500 sq. ft. Section 302 herein elaborates on the size of pipe required relative to the size of the foundation. Subfloor preparation Advisory: Where the gas permeable airspace is not isolated from indoor air, controlling the destination of soil gas is often not possible, especially without a fan. Section 401 uses the term “Soil Gas Collection Plenum” to portray an airspace that is enclosed on all sides, top and bottom. Section 402 (Sub-membrane) and Section 403 (Sub-slab) elaborate on requirements for gas permeable layers and soil-gas-retarders that will resist air movement between soil and indoor air. Vent pipe (common problem) Advisory: Routinely, air intake openings into the vent pipe below the slab are found to be clogged or partially obstructed. An unobstructed air pathway into the vent pipe is critical for controlling soil gas. Section 402 and Section 403 elaborate on options and requirements to ensure free flow of soil gas. For example, perforated pipe is now required to be added to the air intake openings of “T” fittings beneath the slab. Fan location (common problem) Advisory: Where pipe passing through the attic is not accessible for mounting a fan, systems must be invasively altered or abandoned when fans are added. Section 701 places requirements on fan location accessibility and how to handle fans in conditioned attics. Openings between a crawl space and indoor air Advisory: Because airtight closure between a crawl space and indoor air is not possible to achieve, sealing partitions, floors and hatches between the two air spaces has proven to be ineffective. Radon entry from a crawl space into living space remains unabated because negative pressure inside the building, compared to within a crawl space, remains unabated. Passive depressurization system Advisory: Passive radon control systems are not normally capable of continuous soil gas depressurization to consistently stop radon from entering a home. For convection upward flow of air to exit the top of the pipe, and thereby draw air in at the bottom, air temperatures within the vent pipe would need to remain consistently warmer than outdoor air. As this is a fluctuating condition, any depressurization achieved is intermittent. Bottom line Installations that adhere to requirements in ANSI/AARST CCAH and RRNC have a better chance to passively achieve prolonged periods of depressurization with overwhelming confidence that adding a fan will reduce radon concentrations, in virtually any home, to below the national action level.