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  • Writer's pictureSquare One Inspections

Yankee Mitigation: Phase 1

As a twelfth generation Mainer (or the land that would eventually become Maine) I bring DIY and Yankee Ingenuity to a whole new level. No, I would never advise any of our customers to mitigate high radon levels without working with a licensed radon mitigation specialist to reach the absolute lowest possible level, but will always suggest homeowners to do anything they can to reduce radon exposure. As shared in a prior blog post, radon is like the sun. The more you are exposed, the greater the health risk. Exposure is not avoidable as radon exists in our everyday environment (even outside), but it can be managed and minimized.

My family lives in a 1978 Garrison with a full foundation. Our basement is partially finished and my kids use the space to hang out while we use it to do laundry and keep my tools. We tested the basement in 2017 with readings of 2.3 pCi/L. The EPA recommends homeowners to take action when radon in air levels reach or exceed 4.0 pCi/L. A home with a radon mitigation system professionally installed will often reach levels below 1.0 pCi/L. That's what I'm working towards but curious how each modification impacts radon levels before an active radon mitigation system is installed.

In December 2022, I tested the basement again and levels reached 5.1 pCi/L. Yikes. Why the change? The Maine state-certified radon tester in me says it's due to underground rivers and groundwater changes as well as soil disturbance from area homes and utilities. The home inspector in me points to unintended consequences from energy efficiency improvements I have made to our home. We've lived here for 18 years and do all work ourselves. OK, I do all the work myself. My wife just helps me prioritize (tells me what to do).

I can think of three specific improvements we've made that would unintentionally increase radon concentrations in our home.

  • Sealing the attic hatch and all vents/lights when we added insulation to our attic

  • Replacing a drafty French door

  • Installing an insulated, airtight door at the base of our bulkhead

By design, each of these changes sealed conditioned (heated or cooled) air from leaving, essentially trapping it inside. Unfortunately, accumulated radon becomes trapped with it. This is great for energy efficiency, but bad for our health unless we do something.

Phase 1: Sealing The Basement

Before I reach out to a licensed mitigation specialist to install an active radon system, I thought I'd run a test. In January 2023, I sealed both (yes, I have two) dormant sump pits in my basement floor. I also ran a bead of silicone caulking around the entire perimeter (or at least what I can get to) where the floor meets the walls. About half of the floor/wall joint could be sealed as the basement is partially finished and not accessible. Sump pits and cracks/joints are the most obvious points of radon intrusion.

Radon gas is released from uranium in the soil and seeps into the home via any crack or gap in the foundation wall or floor that is in direct contact with soil. When a door or window opens anywhere the house, air exits the home and needs to be replaced. That replacement air comes mostly from gaps and cracks in doors/windows, bathroom vents, dryer vents, around oil supply lines, spigots, chimneys, etc. Another source of replacement air that is less obvious is through basement gaps and cracks. These cracks provide radon gas through hydrostatic pressure due to ground water rising and moving below the foundation.

All told, the first phase of my "Yankee Mitigation" was under $50. This included a roughed-in mitigation system made of a PVC elbow and a section of 3" PVC with cap (see below). New homes are required by code to have a roughed in radon system. That wasn't the case in 1978. I installed this in one of my sump pits. For Phase 2, I'll attach a pipe to this that will vent above my roof line on the outside of the home. This passive system would then be the path of least resistance for radon gas pushing up from below. Instead of the cracks I can't seal in the finished space, the gas would flow to the vent and exit the home.

The radon reduction from sealing the basement was impressive, and a good start. My radon levels dropped to 4.1 pCi/L from 5.1 pCi/L, or a 20% decline from my starting point. The conditions are nearly identical and the effort was minimal. Again, I'm looking for levels below 1.0 pCi/L, not just below the EPA-recommended action level. I've got more work to do.

Stay tuned to see the results of phase two when I passively vent the gas through my newly installed PVC passive vent.

Thanks for reading,


Square One Home Inspections


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