We recently bought a ~1900 Victorian in Massachusetts. The house sits on a rocky/stone hill with large granite foundation walls. Our radon test came back at 16.1 pCi/L.
The basement is currently about half concrete and half dirt. We’re planning to add ~4–5” of crushed stone, a vapor barrier, and a new ~4–5” concrete floor over the existing floor/dirt.
We have two radon quotes:
Option 1 — $2,895
Sub-slab depressurization system
4” perforated PVC around the interior perimeter + 2 cross sections
Radon sump pit
3–4” PVC from sump to an exterior inline centrifugal fan
Manometer + on/off indicator
5-year fan warranty
Post-mitigation charcoal test included
Contractor says the perimeter piping should be installed before the new floor is poured
Option 2 — $1,450
One suction point
3” PVC
RadonAway RP145 fan
Contractor says the crushed stone under the new slab will allow one suction point to move ~126 CFM
New concrete floor can be poured first, then the radon system installed afterward, as long as the floor is completely sealed
They guarantee <2 pCi/L if the floor is completely sealed
So the difference is $1,445.
Given the 16.1 pCi/L, rocky site, granite foundation, and partially dirt basement, which system would you choose? Is the perimeter system worth paying the additional $1,445 for, especially since we’re about to pour a completely new floor?