My home is a conglomeration of numerous additions built from 1888 (original), 1989 (includes finished basement), and 1994. Except for the 1989 construction, all floors are built over dirt crawl space.

As part of an extensive home renovation project, I have installed 4″ perforated PVC under floor radon mitigation piping in crushed gravel covered with new 6 mil fully sealed poly vapor barrier in all crawl spaces. This piping is also extended to underneath the finished basement concrete slab. The piping is brought together into a single line to terminate in a sump basin with a sealed lid as collection point. From there it is exhausted through a solid stack assisted by a 150 cfm in line fan located in the attic near the point of roof penetration. I plan to install a sump pump in this basin with 1 1/2″ drain line – also sealed through the sump lid – routed up and out through the perimeter rim joist to drain away from foundation. This piping will include a check valve located 12″=/- above the lid. Will I need to provide ventilation for make up air to the pump? Or will the Radon Mitigation air suffice? If not how best to provide make up air without defeating the air tight seal for radon gas?

Thanks for your help.

Greg

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