SGM-SF_2017with 12/20 Revisions

Sealing (revised 12/20) 28 ANSI/AARST SGM-SF 2017 (with 1220 revisions) Soil Gas Mitigation Standards for Existing Homes 7.6.7 Wood components Any wood installed as part of a mitigation system that directly contacts masonry or soil, such as when employed to secure a membrane, shall be resistant to decay and insects or otherwise protected. 7.7 Sub-Membrane Depressurization (SMD) In addition to all requirements in Section 8.6 , soil gas retarder membranes associated with SMD shall be sealed in accordance with Section 7.7.1 through Section 7.7.4 to result in a closed soil gas collection plenum under the membrane that resists air movement between soil and air above the membrane. 7.7.1 SMD—Seams The seams between adjacent membrane sheets shall be overlapped and sealed with a compatible sealant or a caulk complying with ASTM C920 class 25 or greater, or a method such as membrane tape recommended by the manufacturer that results in an equivalent durable bond. 7.7.2 SMD—Pipe penetrations The opening around penetrations of a soil gas retarder for ASD duct piping and other utility pipe penetrations shall be fully closed using materials and methods that result in permanent closure. Note—Gasket fittings, pipe clamps, roof flashing or an appropriate sealant are commonly used. 7.7.3 SMD—Walls and foundation supports Membranes attached to foundation walls and at penetrations for foundation support components shall be sealed in a manner to resist soil gas movement between the soil and air above the membrane, to include: a) For flat wall surfaces, the membrane shall be sealed to the foundation walls and supports with a caulk complying with ASTM C920 class 25 or higher or equivalent method. b) For irregular surfaces, alternative materials and methods are permitted so long as durable closure of the soil gas collection plenum is achieved. 7.7.4 SMD—Inaccessible areas When portions of the crawl space cannot be accessed or have insufficient height to work in a safe manner as established by the Occupational Safety and Health Administration (OSHA) or other authorities, the edges of the membrane within the boundaries of accessible areas shall be closed. Where it can be demonstrated to be warranted, systems are permitted with a portion of the membrane edges to remain unclosed. Because this mitigation design inevitably combines sub-membrane depressurization (SMD), crawl space depressurization (CSD) and/or soil gas dilution, open membrane edges shall be disclosed to the client(s) in accordance with Sections 10.1.1 e (Information package) and 13.7.2.1 e (OM&M manual) along with justification for the design. Such design and installation shall also meet any additional requirements in Sections 6.1.4 ( Non-habitable air spaces) and Section 12.6 ( Soil gas dilution) . Note—The larger the area addressed by Sub-membrane depressurization , the greater the effectiveness of soil gas control while minimizing adverse effects of energy penalties and moisture within the crawl space . 7.8 Drains 7.8.1 Drains to soil Informative advisory —It is recommended that a one-way flow drain or equivalent method with adequate flow capacity be installed for any drain that discharges directly into the soil beneath the slab, through solid pipe to a dry well, or has other exposure to the soil. Considerations to weigh regarding use of one-way flow valves include: (1) potential for debris to clog the valves and designed capacity of the valve to drain adequate volumes of water, and (2) whether the airflow leaks between soil and indoor air could contribute to backdraft of atmospherically vented combustion appliances or defeat efforts to establish PFE .