CC-1000_2018

Soil Gas Control Systems ANSI/AARST CC-1000 2018 in New Construction of Buildings 3 2.27 soil gas vent system, n— Individual and complete configuration for controlled soil gas venting that includes exhaust vent piping extended from gas permeable materials within a soil gas collection plenum(s) to the system exhaust at the roof. 2.28 subbase, n— A layer of gravel on top of the subgrade. 2.29 subgrade, n— Native soil (or improved soil). 2.30 system, n— See Soil Gas Vent System 2.31 trunks, n— Air duct piping. See Main Trunks and Secondary Trunks 2.32 vent piping, n— See exhaust vent piping SECTION 3: REQUIREMENT SUMMARY 3.1 General Soil gas control shall be designed and constructed for all portions of foundation systems where there is enclosed space immediately above crawl spaces and slab-on-grade or basement slabs. 3.2 Soil gas vent systems required Soil gas vent systems shall be constructed for each ground contact portion of the building except garages ventilated in accordance with Section 4.8 . Each soil gas vent system shall include exhaust piping extended from inlets within soil gas collection plenum(s) to an exhaust location at the roof, in accordance with Sections 4 through 10 . 3.2.1 Capacity Each system shall be sized with no less the capacity needed to allow a fan-driven soil gas depressurization system (ASD) to transport air volumes sufficient to establish a vacuum under each slab or soil gas retarder . 3.3 Air pressure within the building Building design shall include a review of air pressure relationships expected to result from individual HVAC systems and building features that can naturally induce negative air pressures (e.g., building height, elevator shafts and stairwells). Corrections shall be made, as needed, to control the influences of building air pressure on soil gas entry in accordance with Section 11 . 3.4 Materials and specifications All materials specified for piping and gas permeable aggregates that are different from materials intended for the building design shall be appropriate for similar structures including acceptable tolerances for weight distribution across aggregate and piping below the slab. A qualified structural professional shall be consulted if there are uncertainties in meeting this requirement. 3.4.1 Changed designs When changes to the mitigation design are required due to the needs of structural systems or other building systems, the changed design features shall retain system capacity required in Section 3.2.1 . SECTION 4: SOIL GAS COLLECTION PLENUMS 4.1 General Each soil gas collection plenum shall contain a gas permeable layer meeting specifications stipulated in Section 5.5 and be constructed with surrounding surfaces that sustainably restrict airflow between the gas permeable layer and spaces outside the enclosing surfaces of the soil gas collection plenum. Figure 4.1 Example construction of plenum 4.1.1 Plenum bottom (e.g., subbase or subgrade) The bottom of each plenum shall be constructed to achieve natural closure by way of earthen materials or geosynthetic methods in accordance with Section 5.1 . 4.1.2 Plenum sides (e.g., foundation walls) Openings in the surrounding sides of each plenum shall be closed in accordance with Section 5.2 . 4.1.3 Plenum top (surface facing interior spaces) The top of each plenum shall be closed as specified in Section 6 to result in a continuous closed barrier between soil gas and airspaces within the building. Concrete floors that form the plenum top shall be sealed in accordance with Section 6.2 . Soil gas retarder membranes over earth that form the plenum top where building design does not include concrete floors shall be installed in accordance with Section 6.3 . 4.2 Plenum size calculations The size of each individual plenum shall first be calculated from the inside perimeter dimensions of the surrounding foundation walls. 4.2.1 Divisions Utility piping, ductwork, thickened slabs, grade beams or other obstructions that restricts airflow across a gas permeable layer shall be deemed the edge boundary of a plenum and thereby divide the gas permeable expanse into two or more individual plenums. 4.2.2 Foundation drain systems Exterior foundation drain systems that connect to soil gas collection plenums under the building shall be calculated for size based on the area of wall and foundation surfaces that adjoin permeable materials constructed to enhance groundwater drainage. See Section 5.3.4 . 4.3 Soil gas vent systems per plenum size An independent soil gas vent system with an exhaust pipe extended from the soil gas collection plenum to the roof shall be installed with exhaust pipe sizing no less than specified in Table 4.3 for each individual