Everything a 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.

EPA Guideline

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)

Health Effects

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.

Variability

Seasonal, increasing in colder weather. Winds perpendicular to ridgeline increase radon. Key concepts: Stack effect, combustion air, frozen ground, Bernoulli lift.

Atomic Factoid

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.

Radon-Resistant Construction

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?

Sarah Worsham a year ago

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.

By regulation, radon fans must be located outside of the conditioned space of the home.

The regulation stipulates that the exhaust must extend above the roofline. The idea is to keep the exhaust gas from coming back into the house or impinging on patios, walkways, play areas, etc. There are three basic requirements: The exhaust must be

(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.

As long as the system is running, the air exiting the pipe keeps rain and bugs out. The system exhaust must be vertical, and upward. The rest of the system is designed so that it pitches back down toward the suction point, so that any water in the system drains back into the soil. Caps and other diverters can cause freeze-up problems from condensation when it’s cold out. Did you know: radon systems can expel hundreds of gallons of water vapor each year?

PVC piping is the most suitable material for the job. Metal downspouts are not intended to be used for gas exhaust applications, and the joints cannot be permanently sealed (they require frequent re-sealing). Downspouts also tend to ice up in the winter, disabling the system just when you need it the most.

Our standard sump covers are transparent, so you can shine a flash light into the sump pit to verify that the sump is working.

Everything a Michigan Builder Needs to Know About Radon