CC-1000_2018

CC-1000 Companion Guidance (1-2018) CC-1000 Companion Guidance CG Page of 12 Informational 3 CC-1000 Discussion SECTION 5: PLENUM CONSTRUCTION 5.1 Close the bottom of the soil gas collection plenum(s) . Design & Installation Detail Advisory — System effectiveness and energy efficiency is compromised when a sizable volume of unintended air is available to enter the plenum cavity. Most subgrade materials will not require extra care to achieve a controlled depth for gas permeable conditions. Examples of concerns include expanses of highly permeable aggregates or rock crevices that extend laterally or vertically into the earth. For evaluating native soil, fill materials or constructing a soil gas boundary: Earthen aggregates cross a line for use in construction standards published by ASTM and AASHTO. The same line that distinguishes poor hydraulic conductively for water is applicable for soil gas. Obstructed hydraulic conductively is associated with earthen aggregates that contain more than: • 35% of sand, rock fragment fines, clay and silt; or • 10% high plasticity clay or silt (e.g., expansive soil with a liquid limit ! 50%) 5.2 Close the sides of the plenum(s) before installing gas permeable materials 5.2.1 Gaps and penetrations through walls and footings 5.2.2 Waterproofing 5.2.3 Gaps and seams on exterior wall surfaces 5.2.4 Hollow masonry unit walls These items do require more attention to workmanship detail than normally provided. Advisory — Restricting soil gas migration from the side surfaces of the gas permeable layer aids control for the migration path of soil gas and energy efficiency. 5.3 Foundation drain systems. Advisory — Where interior water drainage components are connected to an exterior foundation drain system: • Plenum size calculations relative vent pipe size limits on air movement capacity must include the foundation drain system. • Restrictive closure can be required for openings to outside air at both water receptor and water disposal locations. 5.3.2 Water receptors (ground or surface water) 5.3.3 Water disposal (over ground or storm sewer) 5.3.4 Exterior foundation wall drainage Most foundation drain systems will not require significant modification to the soil gas control system or foundation drain systems. However, robust drain systems with multiple openings between the gas permeable layer under the building and outside air are a major concern. Advisory — Foundation drain systems that open to daylight or storm sewers can reduce or defeat control for the migration path of soil gas and energy efficiency of the design. 5.3.3 Water disposal (over ground or storm sewer) 5.3.4 Exterior foundation wall drainage 5.3.5 Foundations below the water table (e.g., wetlands) Various requirements do not apply to foundations that are expected to be below the water table for extended periods of time on a routine basis. !