What is the protocol for mitigation of radon on a crawl space home? Thanks in advance.
We don;t see allot of systems here. The ones that are in place are usually poorly done. I would research active and passive means. Often times it involves installing plastic with sealed well sealed joints, sealing to piers and foundation. There is a pipe with holes under the plastic that goes up through the roof to exhaust the soil gasses. The passive system uses the natural stack effect but a active system would use a fan that is placed in the attic to create the draw. If you can’t go up through the house the pipe can be run on the exterior with the fan outside and the pipe going up above the roof line. That’s the basics that I know of.
DO know if this help Joe but here you go
If the crawlspace has a concrete slab, then it’s just a plain old sub-slab depressurization system.
If the crawlspace is dirt, you have to create a slab using thick plastic sealed to the walls, and then depressurize under it. On top of that, a barometric backdraft damper which lets outside air into the crawlspace to replace the air you are removing might be needed.
If the crawlspace is outside the heated envelope of the house, simple ventilation might do it.
Thanks to all.
Sub-membrane depressurization, include side wall if needed and garage slab if there is one.
Drain tile depressurization as a last attempt.
Sub membrane and drain tile depressurization systems really need make-up air for safety IMHO. Many will disagree with me.
I know some will disagree Nick but it still would be nice to see the reasoning. I don’t deal with Radon here in SSM On only outside town areas but will agree with you based on some talks and readings on another MB.
Sub-membrane and drain tile depressurization systems pull so much air out of the house that without make-up air, you can backdraft the fossil fuel burning appliances/furnace. That’s my thinking and why I believe barometric backdraft dampers and fresh air inlets should be used more often by installers.
Anyway, for home inspectors there is a good radon mitigation SOP and reporting form (free) here: http://www.nachi.org/comsop.htm#18
Key point in the article is proper ventilation
**Geographic and Residential Risks
**The amount of radon emanating from the earth and concentrating inside homes varies considerably by region and locality, and is greatly affected by the residential structure as well as soil and atmospheric conditions. Nearly every state in the United States has dwellings with measured radon levels above acceptable limits. The EPA estimates that 6% of American homes (approximately 6 million) have concentrations of radon above 4 pCi/L. Areas of the country that are likely to have homes with elevated radon levels are those with significant deposits of granite, uranium, shale, and phosphate, which are all high in radium content and, therefore, potential sources of radon gas. However, due to the many determinants of indoor radon levels, local geology alone is an inadequate predictor of risk. The only way to determine indoor radon concentration is by testing. Other factors that predispose homes to elevated levels of radon include soil porosity, foundation type, location, building materials used, entry points for soil gas, building ventilation rates, and source of water supply. Further research is being conducted on ways to predict which homes are most likely to have significant levels of radon.
Radon Level **If 1,000 People Who Smoked Were Exposed to This Level Over a Lifetime… ** **The Risk of Cancer From Radon Exposure Compares to… ** What To Do: STOP SMOKING and… 20 pCi/L About 250 men or 143 women could die of lung cancer
> 100 times the risk of drowning Consider fixing between 2 and 4 pCi/L 8 pCi/L About 132 men or 66 women could die of lung cancer > 100 times the risk of dying in a home fire Consider fixing between 2 and 4 pCi/L 4 pCi/L
About 66 men or 33 women could die of lung cancer > 100 times the risk of dying in an airplane crash Consider fixing between 2 and 4 pCi/L 2 pCi/L About 33 men or 16 women could die of lung cancer > 2 times the risk of dying in a car crash Consider fixing between 2 and 4 pCi/L 1.0 pCi/L About 16 men or 8 women could die of lung cancer (Average indoor radon level) (Reducing radon levels below 2 pCi/L is difficult) 0.4 pCi/L About 8 men or 4 women could die of lung cancer (Average outdoor radon level)
*pCi/L: picocuries per liter. If you are a former smoker, your risk might be lower.
**Radon Risk Evaluation Chart if You Have Never Smoked** **Radon Level** **If 1,000 People Who Smoked Were Exposed to This Level Over a Lifetime... ** **The Risk of Cancer From Radon Exposure Compares to... ** **What To Do: STOP SMOKING and...** 20 pCi/L About 33 men or 20 women could die of lung cancer > 2 times the risk of being killed in a violent crime Consider fixing between 2 and 4 pCi/L 8 pCi/L About 13 men or 8 women could die of lung cancer Consider fixing between 2 and 4 pCi/L 4 pCi/L About 6.4 men or 4 women could die of lung cancer > 10 times the risk of dying in an airplane crash Consider fixing between 2 and 4 pCi/L 1.0 pCi/L About 1.6 men or 1 woman could die of lung cancer The risk of dying in a home fire (Average indoor radon level) (Reducing radon levels below 2 pCi/L is difficult) 0.4 pCi/L Less than 1 person could die of lung cancer (Average outdoor radon level)