Everything a Michigan Builder Needs to Know About Radon
What It Is
A heavy, inert radioactive gas formed from radioactive decay of radium (mainly from glacial outwash). Decays into radioactive “daughter” particles (polonium, bismuth and lead) that can lodge in the lungs.
Reduce average radon level to below the Action Level of 4.0 picoCuries/liter.
Basis for Guideline
Technology-based standard, not health-based. Less radioactivity is always better than more, and you can’t get to zero, so the golden rule of radiation safety applies: “ALARA = As Low As Reasonably Achievable. (Other countries’ standards range from 2 to 22, based on their interpretation of the “R” in ALARA).
EPA Real Estate Test Protocol
Test in basement (worst case and most stable condition)
Leading cause of lung cancer in nonsmokers. Living with X pCi/l gives the lungs the same radiation dose as X chest x-rays per week.
Michigan Hot Spots
The EPA classifies much of southeastern Michigan as Zone 1 (Hot Spot). Several readings near 300 pCi/l. Highest in Washtenaw County is 282 (Textile & AA-Saline Rd.); highest in Ann Arbor is 204 (near the Huron River). See maps.
Building Science Issues
The driving force is primarily the “stack effect” creating a vacuum in the basement that draws soil gas through large and small openings in the foundation and slab.
Basement vs. Living Area
First floor radon concentration is typically 50-70% of basement level, second story 60-80%. Key concepts: Stack effect, neutral pressure plane.
Seasonal, increasing in colder weather. Winds perpendicular to ridgeline increase radon. Key concepts: Stack effect, combustion air, frozen ground, Bernoulli lift.
Imagine a radon atom being drawn through a crack 0.005 inches wide. Now imagine a basketball in the Grand Canyon. Conclusion: Sealing alone is ineffective. Preferred method is to depressurize the draintile, creating a soil gas collector. Dilution & pressurization via heat-recovery ventilator may work, but probably not if the baseline radon is over 10 pCi/l.
Minimize openings to soil, minimize stack effect (possibly by installing a passive stack from draintile). DO NOT “vent the sump” as so many builders do — that’s extra cost for no benefit. Under no circumstances should you use a pedestal style sump pump, even if not using radon-resistant construction.
EPA Design Standards (Nonbinding)
Vacuum fan and all downstream piping outside or above any conditioned space. Exhaust: 10 ft away or 2 ft above all windows, above eave. Include system monitor & label.
Radon Service Agreement (Protech Exclusive)
Our Radon-Resistant Construction package. Low cost, no-hassle. No last minute panics during final punch list. The full EPA test series is conducted after closing, and whatever further steps may be needed to meet the EPA Action Level will be done at no charge. Typical price for custom home is $400-500 (somewhat more if you want us to run the stack).
Have A Question About Radon Treatment?
Super quick and efficient service of installing a radon mitigation system in the house we were selling. The installers were very knowledgeable and explained the system and the information to pass on to the buyer's. Definitely would recommend.
(a) at least ten feet off the ground,
(b) above the eave (not necessarily the edge) of the roof, and
(c) either ten feet away from, or two feet above, windows.