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Are Sierra Green Builders Ready for Radon? 

Jeff Miner
Radon At Tahoe


Radon, the Noble gas, Rn 222, has been part of the Sierra Nevada for millions of years.  Radon is a radioactive decay product of Radium, which itself is a decay product of Uranium.  Uranium is commonly found in granite rock and granitic soils, which we have in abundance in the Sierra Nevada.  In fact the entire Sierra batholith, all 5,000 feet thick, 100 miles wide and 300 miles long of granite (or there about), produces a lot of radon.   The good news is the population density in the mountains is low, relative to most urban areas.  The bad news is that WE live up here.  As do our clients.  So we, as builders and architects, have to be more aware and better educated about how to test for and prevent radon from entering the houses we build, even green houses.


What s the Problem?  Radon does not stay buried in the ground like its parents Radium and Uranium.  Being a gas with a specific gravity slightly less than the surrounding soil, radon makes its way up through spaces in the soil and eventually vents itself up and is dispersed into the atmosphere at relatively low levels.  However, when radon enters a house through a crawl space, slab or basement, especially an energy conserving, tight house, it can build up inside the house to dangerous levels.  The U.S. Surgeon General has determined that Radon is a Group A carcinogen and can cause lung cancer.  In fact he estimates that 21,000 people die each year from radon induced lung cancer.  The U.S. EPA has set 4 pCi/L (PicoCuries per liter) as the action level for when home owners should fix their homes.  Many house in the Sierra Nevada test above, some well above, the action level.


The mechanics of how radon enters a home (it s actually sucked into the home through the Stack Effect " hot air rising), or the biology of how radon cause lung cancer (it s the damage to lung tissue when the radioactive decay products of radon (polonium 218 and polonium 214) themselves decay and give off alpha particles while stuck to a dust particle in the bronchial tubes), or how to mitigate an existing home or how to Build radon out of a new home, etc. will have to be subjects for future articles or for independent research by those of you who are at least interested enough to have gotten this far in this article.  (My web site,, has more info and is a good place to start your research).


My goal for this article is to get to this very interesting question:  If radon is such a big problem in the mountains, why are so many houses (some very nice, expensive and green houses) being built without one word of radon mentioned in the plans and without radon being built out during construction and without radon being tested for after they are built? 


Regulation.  For starters radon is not regulated.  None of our counties in the Lake Tahoe area (El Dorado, Placer, or Nevada) and none of the cities (Truckee, Tahoe City, Incline Village, or South Lake Tahoe) have radon ordinances requiring radon mitigation systems that meet the EPA protocols.  This is not true in other parts of the country where entire states such as Minnesota, and many cities and counties have detailed radon regulations and inspections.   

LEED.  For green builders who are hoping for a LEED certification, radon is listed as number nine under Indoor Environment Quality and is worth only one point.  Radon mitigation is mandatory if the house is in EPA region 1 (high radon potential).  El Dorado, Placer, and Nevada counties are listed as region 2 (moderate radon potential).  Builders unfamiliar with radon mitigation may be tempted to earn their one point in other ways rather than designing and building a radon mitigation system. 


The EPA National Radon Map was completed 20 years ago and lists high, moderate, and low radon potential by county for the entire U.S.  It has become the default standard as to radon risk and is relied on by the USGBC for LEED certification, for real estate hazard disclosure reports, and for other government and business radon risk determinations.  This would be great except that the map is out dated and often inaccurate.  More recent and more accurate studies have been done but organizations tend to rely on the tried and true, even though it s not up to date.


The California Geological Survey released Special Report 211 this year titled Radon Potential in the Lake Tahoe Area, California.  It is available at and at the CGS web site.  In the tri-county area of the Tahoe Basin (California side) 11,269 out of 24,756 homes are in a very high radon potential area, that s 46%!  In El Dorado County it was 75%.  There are over 28,000 people living in a very high radon potential area in the Lake Tahoe region alone.  Yet the EPA map shows all of El Dorado, Placer, and Nevada counties as only moderate radon potential.  And LEED certification is based on the EPA map.


I would hope that SIGBA might understand this problem and encourage USGBC to use more accurate standards when determining if an area is high, moderate or low in radon potential.  So far, my efforts at bringing this matter to the attention of the USGBC have been met with unreturned emails and phone calls.  And I would hope that SIGBA members would understand radon and how to build it out when they design and build homes in the Sierra Nevada.



Jeff Miner has lived in the Sierra Nevada for 39 years.  He lived in his home in South Lake Tahoe for 24 years before he tested it for radon and found high levels.  He did some research, mitigated the radon himself and lowered the levels from 6 pCi/L to 1 pCi/L.  In 2005 he started Radon At Tahoe to help others test their houses for radon and fix it if high.  To become more professional he became a trained radon mitigator and has been certified by California, Nevada and the National Environmental Health Association - Radon Proficiency Program since 2005.  Prior to his radon conversion , Jeff ran the IT department for the Lake Tahoe Unified School District and before that he and his wife founded and ran Grass Roots Natural Foods on the South Shore.

Link to the California Geological Survey to download the complete report and maps.


Mail can be sent to: SiGBA P.O. Box 4245 Truckee, CA 96160

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