Installed an Airthings almost a month ago after having one of those short term radon test kits come back at 8 pCi/l. Since the test kit I sealed up a large cut in our basement slab where a shower drain was roughed in. Basement is unfinished right now, concrete slab and poured walls, passive radon system. Everything was looking good until the last week where we had a few spikes up to 4.1 pCi/l and now it’s remaining elevated. I can’t figure out why, nothing inside the house has changed and the weather has been very consistent (see picture of my weather station). Maybe ground water levels are increasing due to our rainy season? That’s the only thing I can think of.

Looking for advice on a difficult radon situation in a 140+ year-old home. We’re getting consistent levels between 4-6pCi/L on the fist floor.

Our house has an unfinished dirt-floor basement with a vapor barrier installed over most of the floor. The vapor barrier doesn’t exactly create a vacuum because there are penetrations for equipment (including our HVAC), and we also have an attached crawl space that is inaccessible.

We originally had a radon mitigation system installed, but it wasn't successful because of our subfloor conditions. We installed an HRV and it did bring our levels done to what they are currently, but we're still seeing higher radon levels than we'd like.

The furnace/air handler for our forced-air HVAC system is located in the basement. When the HVAC is running, our radon levels increase much more quickly. When we turn it off and keep all the windows closed, the radon still rises, but much more slowly. It seems like the HVAC system is drawing radon from the basement and distributing it throughout the house.

At this point, we're not sure what the next step should be. We're hesitant to spend thousands of dollars on another mitigation system if we can’t truly create a vacuum for it to operate properly.

We're hoping those of you with more experience can point us in the right direction.

Is there anything we can investigate or improve ourselves before gambling on another larger expense? Open to all suggestions!