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I have a customer who wants a passive radon vent system roughed in. No fans, just the pipes. I have found very little about this system, even from the local building dept. They tell me there is no known radon problem in the county’s jurisdiction. Needless to say, my customer is being ultra-conservative.
the only reference I have to it is Lstruebek’s “Building in Cold Weather Climates” He shows a vent pipe run to the gravel under the slab and vapor barrier, exiting through the roof. He makes no mention if one is adequate(he shows only one in his illustration). This basement is about 1200 sq. ft., and has a gravel base of about 6 in.
Anyone know if one vent pipe is enough?
Thanks, John
Replies
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I was going to post some links but there are so many. Go here and enter "radon venting" and click search. http://www.google.com/
*Have you done a radon test? The test kits are only about $20, last i knew. Maybe that would assuage the customer's worries and keep you from doing unnecessary work. If this is new construction, it would be a good way to get to know the neighbors, to ask to use their basement for the test.
*First the disclaimer: I am not a certified radon reduction contractor, nor have I played one on TV. However, I have installed and operated about 80 soil vapor extraction systems, mathematically modelled both subsurface airflow and atmospheric air pollution, and I'm a pretty good plumber.Taking gstringe's lead, I liked this URL:http://www.epa.gov/iaq/radon/pubs/consguid.html#whattolookforfor readability and content.I would put one perforated pipe down the middle of the gravel layer and transition to rigid PVC before bringing it up near one side of the basement where the fan will be located. I'd transition to rigid pipe because it is so much easier to have leakproof valves and connections. Leave the perf pipe down below the slab. One pipe is sufficient because the pressure drop across the gravel base is so much less than through native soils. The whole volume of the gravel will be under a negative pressure once a fan is connected.Most designers would run the discharge pipe up through the roof like a stink pipe or chimney. Here's a factoid and design detail for your customer who sounds pretty anal. Conservative air modelling computer programs like PTPLU (PoinT source PLUme modelling) presume that if a stack is less than 1.5 times the height of a building and within 5 times the building smallest dimension, then the discharge can be entrained within the wake (air eddy) of the building. An example: If the building is 30 x 40 x 24 high, the discharge stack should either be at a 36 (1.5 x height) feet height or be 120 (5 x minimum dimension) feet away to avoid exhaust possibly being entrained on the downwind side of the building. So running the discharge back underground and daylight outside the building and going 100 feet away before discharging has a slight advantage. Also avoids yet another roof penetration at the cost of some trenching.I'd use one of those in-line duct booster fans to move the air. If the gravel sub-base doesn't daylight anywhere (tighter soils are used for backfill) than you won't need to move much air at all to maintain a negative pressure. -David
*Splintergroupie said "If this is new construction, it would be a good way to get to know the neighbors, to ask to use their basement for the test."FWIW, testing one house won't give any useful information about the house [to be or existing] nest door.I'm told by radon testing subcontractor that it is very common for identical neighboring houses built by the same builder at the same time to have widely differing radon readings.Bob
*Well I've done the Course and have installed a few. David is just about right on except that he skipped a couple steps that I think apply is this case.First, I don't know of any passive venting system that in fact redirects the radon gas out of the building. Yoiu must have some kind of air handling. Inline fans are the thing.Next, check with the local building officials and do the above radon research. It is probable that your customer is acting out of ignorance. They will also tell you what will last and pass inspection in your area. For more on this my favorite radon book is: Protecting Your Home From Radon by D.L.Kladder. This is about 7 years old and is used as the text in several certification courses.If they still want to do something a good rock sub-base for the basement slab that is vented outside the basement with pierced pvc (something like a drain all around the foundation) is the thing. Be sure to use a "vapor barrier" between the slab and the base. This allows the air to work it's way out from under the slab and join the rest of the radon that is in the air all around us.Radon, lots of snake oil here, so heads up. Radon is a real danger in certain areas. But, like termites is not in all areas. So, if it ain't there it is wastefull to install the system.
*Where i grew up in MT, there were several radium mines that people went into to breathe the radon gas and drink the water coming out of the ground. It was quite a cottage industry for the locals, who would turn their houses into part-time hotels. I rented from one of these entrepreneurs and met people who swore to me they'd arrived in wheelchairs, yet after the "treatments" were cured of all manner of ailments, and could walk again. I don't suppose the AMA would get behind it, but it's sure hard to argue with success.On the television PSA's, they warn that radon gas is the second highest cause of lung cancer, and i wonder, How do they know?
*none of the assumptions about radon have ever been proven... it is right up there on the list of voodoo science.. right alongside cancer caused by high voltage transmission linesradon is a naturally occuring by-product of soils.. most of the building products we work with contain radon.. especially the aggregate we use in concrete..the best mitigation systems use CRUSHED rock and 4 inch perf pipe...but... the crushed rock MAY be introducing more radon than is naturally present in the exsiting subsoil...the levels determined by the EPA as being harmful and subject to mitigation are arbitrary... (4 pi)and most of the testing is done in areas tht are not especially frequented by the occupants of the home.. the testing should be done in the bedrooms and teh family room... areas that have a high preponderance of occupation...and here's a quote from one of the links above...((Radon is estimated to cause many thousands of lung cancer deaths each year. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. Only smoking causes more lung cancer deaths. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.))this is bunk... and unsubstantiated by double blind tests.....and there are no medical reports quoted in the links.....if any of the claims about radon were true.. we would have to stop all concrete construction.. most aggregate production,.. and revamp our entire building technology...please show me some validation for the harmful effects of radon.......i'm all ears.....
*Mike, you sound like a tobacco company. ("Smoking doesn't cause cancer.") I agree that there has been both hysteria and profiteering around radon but I know there is a lot of data that more radiation in one's life is a bad thing. Many of EPA's risk assessments (I'm familar with the data on hydrocarbon, solvents, and heavy metals) are very conservative. They use short-term, high-dose data on mice and then throw in a factor of ten to address differences between species, another factor for short versus long-term and often another factor of ten for high-dose versus low-dose. So many of their guidelines are 1000-fold conservative, hence estimates of the cancers caused are way too high. But some people are in houses where radon gives them radiation doses equivalent to an extra chest X-ray each week or each day. This is not good for you!Radon in building materials, concrete, and aggregate? Nope, nothing that compares to underground sources. There are 32 isotopes of radon with halflifes ranging from 2.3 microseconds to 3.8 days; most are from seconds to a few minutes. This means that radon goes away very quickly. When I've got radon in activated carbon, I just let it sit. It's essentially all gone in less than two weeks. The radiation level is higher in concrete and masonry homes because of low concentrations of longer-lived radio-isotopes like uranium salts. These decay over a long time through a series of elements, giving off radiation at each decay until they decay into a stable isotope.The radon in houses that causes a problem is from underground deposits of heavier radio-isotopes that decay and release radon gas. As a gas, it can migrate up to the surface. Or your basement. Or you can pump it into your house from a well and breath deeply of it in the shower each morning. I am confused about how one could possibly conduct a double-blind test on smoking and radon. Certainly the doctor could not be told, but most people would notice if made to smoke a cigarette.Smoking, radon exposure, living at altitude, using birth control pills, and being a flight attendent are all documented risks for cancer. Some large risks, some small risks. Even smoking only kills a third of smokers. A majority find something else to die of first. -David
*This is a foolish and misinformed post. There is a now extensive epidemiologic evidence to support the fact that radon is a carcinogen and a cause of lung cancer. If you are interested, go to the National Library of Medicine web site (http://igm.nlm.nih.gov/) and do a search for radon and you will find more scientific papers than you could read in the next week. You will have a hard time finding a physician or scientist that would even consider disputing this data. I certainly would not claim to be an expert on building construction to prevent radon exposure - I will leave that to the builders. I will, however, not let a misinformed post like this go unchallenged.Jim Roberts, MD
*ok dave & jim .. now i know...so.. the next question.... how does that relate to homes, offices, schools , and factories ?
*Mike & Jim,As I understand the Beir IV summary (at the EPA's site, last I looked), the available information is based on miner studies where they were exposed at very high levels for long periods of time.If I understood it correctly (and there's a fair chance I haven't) the issue is really whether they can accurately project from those levels to levels commonly found in homes.Any comments?Bob
*bob... that was my UNINFORMED impression also...and the double blind part was that the miners had been exposed to so many other things... including a preponderance of smokers.. and .. contrary to the statements about aggregate..in the northeast .. most of the aggregate is granite... and teh raadon readings are high enoug to move the needle...most of the testing i have seen is that the background radon level is higher than they thought when they set the levels..my exposure to the radon ((problem)) is that even with certified testors... the acuraccy of the tests..and the ability to influence the tests in homes and business and public spaces.. makes most of the mitigation ineffective....luckily.... our standard construction methods with crushed stone... perf-pipe for drainage below the slabs.., 6 mil vapor barriers.. etc makes it relatively easy to retrofit the mitigation methods..and once again... i'm eager to hear alternative positions...especially as they relate to the world of building and structures and homes.....
*Mike there is radon essentially everywhere. The problem is because in a house or structure the concentration of the radon becomes too high for good health. Now, how much is too much? The ground rule there is to do the testing on other species and apply to humans. That the EPA has done. Because it takes a lot of years for the effects of high level radon exposure to manifest it is only sensible to not wait for definitive testing of the general population before taking remediation steps.Since we do so many different things that are hazardous to our health, like eating Big Macs or smoking it is tough to determine a specific individual's result from being exposed to high cocentration radon. But, we can do population wide projections.My earlier post was not to downplay the problems with radon. It was to say, from my knowledge, that from looking at a map and from the post it appears that radon may not be a big problem in that part of Ohio. Also, that passive systems don't work very well unless radon levels are pretty low. If you need to mitigate radon in high problem areas like the Rocky's then you need active systems. Also, to say that it is a waste of money and resources to install a radon mitigating system if it is not needed. It cost both to manufacture, distribute, install and maintain a system.
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I have a customer who wants a passive radon vent system roughed in. No fans, just the pipes. I have found very little about this system, even from the local building dept. They tell me there is no known radon problem in the county's jurisdiction. Needless to say, my customer is being ultra-conservative.
the only reference I have to it is Lstruebek's "Building in Cold Weather Climates" He shows a vent pipe run to the gravel under the slab and vapor barrier, exiting through the roof. He makes no mention if one is adequate(he shows only one in his illustration). This basement is about 1200 sq. ft., and has a gravel base of about 6 in.
Anyone know if one vent pipe is enough?
Thanks, John