In this 1800-built Andover home with cement foundation and radon level of 4.3 pCi/L, we installed a one-pipe mitigation system tailored to its unique layout and encapsulated crawl space. The interior run leads into the garage attic, where the homeowner will ensure power is available before the job starts. Two small areas—3x6 feet and 48x40 inches—were prepped for clean space installation. Crack and hole sealing were also part of the prep work to ensure airtight results in this historic structure.