I own a 100 year old house with about 20" thick stone walls in basement. The radon level was at 11. We had poured a new concrete floor in 1995 with a plastic drainage tile around the inside perimeter. So installed a 4" pvc through the floor and into the tile. The pvc exits thru a basement window that we put lexon in instead of the glass. We used the Fantech fan. The radon level is down to 1.5. I am happy with the system.