My first question is:How did you gain access to this forum. This for radon professionals who subscribe to AARST.
Call your State or local Health Dept. and have them recommend a certified radon mitigator you can consult. And Please, stay away from the internet.

I agree with Ed but George brought up a topic that has bothered me for years.
The outdated and inaccurate EPA Radon risk map. I live and mitigate in the Black Hills in western South Dakota. The EPA map shows this area as 2 where radon levels are expected to be below 4 pCi/l. Uranium mining and exploration has been occurring here since the 1940s. The largest population centers are all in the uranium bearing formations that surround the Black Hills. We see neighborhoods where all the homes are in triple didgets, some above 500 pCi/l. In the central hills, well away from those formations, levels above 1,000 have been seen.
The USGS radon map clearly shows this risk area yet, with all the testing since 1993, the EPA map has not changed.
The EPA should at least update their map with the USGA data. Better yet they should incorporate data from radon testing over the quarter century of testing that has occurred since 1993. Homeowners and local government agencies look at that map and use it to make decisions about testing, radon resistant construction and building ordences.

Hi George, I was unaware that this forum was only for AARST members. I am glad you are seeking out information about radon before building! While studies show that radon resistant new construction systems perform better when installed by knowledgeable (certified usually qualifies) it certainly doesn't hurt to have some knowledge yourself. The state radon office or the national radon program is a great place to start. This forum is also a great place for radon info. To answer your question about radon being heavier than air...It is a misconception that radon settles downward because it is a heavy atom. Air is a mixture. Radon is one of the atoms or molecules that make up air (nitrogen, oxygen, etc...). The atomic forces are stronger than gravitational forces so radon stays within the mixture and dissipates into the atmosphere when exhausted out of a radon system. Radon has a tendency to be higher in basements, not because it is heavier than the other things in air, but because it is closer to the source, the soil.

Hey George. Very valid question. We hear it all the time. Sure. Radon is roughly 7 times heavier than air. However, we are talking on such a small scale, that any slight breeze or natural air current will wisk it away. The main reason we want the vent stack to be up above the eve line more has to do with natural pressures of the structure. The lower on any building you go, the more air wants to get pulled in to said structure through what’s called the stack effect. Imagine any building as a piping system for radon. Where at the top, hot air is forcing itself out through the roof, and then to replace that air, the bottom is actively pulling air in from the surrounding soil. The whole point of a radon system (active of passive) is to try to give that air a path of least resistance so the radon (and moisture and other soil gases) is mitigated to a safe distance. That’s why they don’t call it radon removal, because we aren’t really removing it. We’re just giving it a nice path to dissipate outside. After that natural pressures prevent re-intrusion.

Prettiest option is always to put in the pipe during building so I applauded you know that. An ounce of prevention is worth a pound of cure.

There is a disclaimer for the radon map that is overlooked too often:

"The Map of Radon Zones was developed in 1993 to identify areas of the U.S. with the potential for elevated indoor radon levels. The map is intended to help governments and other organizations target risk reduction activities and resources. The Map of Radon Zones should not be used to determine if individual homes need to be tested. No matter where you live, test your home for radon—it’s easy and inexpensive. Fix your home if your radon level is 4 picocuries per liter (pCi/L) or higher. Consider fixing if your level is between 2 and 4 pCi/L.

The Map of Radon Zones was developed using data on indoor radon measurements, geology, aerial radioactivity, soil parameters, and foundation types. EPA recommends that this map be supplemented with any available local data in order to further understand and predict the radon potential for a specific area."

Most states have updated data and many have updated maps. They should be the first place to get information. One of the problems with maps is their use to downplay the risk and as an excuse for inaction - what is an acceptable level for not venting radon.

REMEMBER, EVEN IN THE LOWEST RISK RADON AREAS, RADON IS PROBABLY THE HIGHEST ENVIRONMENTAL RISK AT THE BUILDING LOCATION.

Thanks for all the info. and when I signed up for this forum it did not say it was just for subscribers to AARST and asked me why i wanted to join. I figured since I answered I was a home builder ( since that is what I will be starting this year) and the Admin approved me it was ok. Any ways I figured where better to get answers than the pros to plan for my build rather than hear-say on the internet where everyone has an opinion on what's right. But again. Thanks for the help and info.

Larainne,
You brought up a very good point that maps can be an excuse to downplay the risk and an excuse for inaction. This is especially true for municipal governments that are under pressure to not add to the regulations. When the USGS map clearly shows it is at high radon risk geologicaly and the EPA map says the opposite, but is supposed to be based in part on geology, it raises questions on the accuracy of EPA information in general. I have had conversations with personnel in the Rapid City code inforcement that believe radon is a hoax. I can slowly get their minds changed but the map is a weapon used by homebuilders to resist new regulations.

Hey,George. Put the piping in as depicted in Appendix F of the Building Code.
Radon is a radioactive gas, and all radiation damage is cumulative over one's lifetime, so the lower exposure is at any given time, the better off one is in the long run. Best guess from EPA is that a properly-done passive system may give as much as a 50% reduction in radon concentrations without a fan.
Radon, like most things, seeks equilibrium concentration-wise and pressure-wise. Venting above the roof allows the gas a pathway from the soil to the atmosphere (as occurs outdoors) without coming through the house.
I do not know if conditioned attic spaces are the norm in your area, but be aware that Radon Mitigation Standards do not allow fans or exhaust-side piping (if needed) to be within the conditioned envelope of the house.The passive piping should be run through a ventilated attic space, or a ventilated space be created within a conditioned attic.

Thanks. Yeah my attic is a conditioned space so I will have to find a way for it to get out and still be in code. maybe run the pipe through a chase to the roof and seal all around the chase inside the attic. Thanks for the info.

lol... just looked at the 2018 (newest code) for North Carolina and appendix F has been deleted..lol.. figures.. Not that I was going to try this myself but At least wanted some kind of idea to maybe suggest a work around.

All,
The Radon ListServe is not just limited to AARST Members; all participants must agree to the Terms of Service.

Good Morning George,
I just wanted to mention, and I am sure that all participants on this forum would agree, that this is the PERFECT time for you to consider becoming a licensed, certified radon measurement or mitigation professional. It is a fantastic add-on to your business, and will allow you to better serve your clients, in the long run. Visit https://nrpp.info/ for more information on this. Good for you for being concerned and aware about high levels of radon!

George,
You’ve received good advise in the previous comments. If you want to read or study a copy of the standard go to https://standards.aarst.org/ . There you will find the ANSI/AARST standards. Go down to the CCAH standard and you can view the details of the standard. There are great similarities to Appendix F with some best practices included. You can view the entire standard at no cost. Of you would like to purchase it so that you have a “hard” only, you can do so.
Since there is no safe level of ionizing radiation, your interest in properly installing a system is prudent.
- David

Good morning George: I would suggest that strongly that you consider from day 1 installing an active system in your new home from the beginning. Recent research here in Canada (CARST 2019) has shown that active radon systems (radon systems with a fan running continuously) save electricity, if the home is being air conditioned.
The entry of uncontrolled moisture from the soil through 70' of cracks or cold joints (that are less then 1/2 the thickness of a credit card) that the air conditioning system use a significant amount of electricity to condensate out. The cost of this electricity is 3 to 5 times the cost of electricity to operate a radon fan all year. Active radon systems not only control radon (when well installed and properly sized) but also control entry of many other unwanted soil gases, methane's, VOC's, old pesticides and also control humidity entry.
The other question that you asked is about the amount of radon that would be in your home based on EPA mapping. Please understand that radon levels are variable house to house year to year and hour to hour and can even change significantly with different occupants.i.e. my mother would not sleep in a bedroom without the window open, (cracked in winter but all the way open in summer while running A/C it drove my dad nuts). Today i would know that if that window was on leeward side of the house (it was) that her radon levels would be up, on windward side they would be lowered. In the 15 years i have been mitigating radon we have seen many neighbors have vastly different radon levels even in tract homes that were built by same builder same year.
Good luck with your new home!

Thanks every one. Since I am the owner / builder of the home I plan to try to do everything I can to make this house safe and last 100+ years. I am placing 8-10" of stone under (2) 1" layers of type 9 IPS foam with all seams taped followed up by a 10-20 mil poly with all seams caulked and taped shut followed up by 4" of concrete. the basement will be considered conditioned space, then the main floor will be conditioned space and finally the roof will be conditioned space with 6" of closed cell in rafters, 7/16" sheathing, 2 layers of 1" poly iso with a all joints taped and a completely sealed layer of peel and stick Water and ice shield with 3/4" batten boards for spaces with skips in between boards to allow air flow and then standing seam metal roof. I had been in contact with someone who built a house similar to what I am doing and he said he had his property tested and didn't find elevated levels of radon and did nothing with it. I was thinking Since the house is considered a conditioned space and usually you can't run a radon evacuation tube through a conditioned space, if I built a chase just for the tube and sealed it with closed cell foam all the way around and put the fan unit on the outside of the building so as to limit the joints in the house is this something that I should bring up to a mitigator as a possible solution? Or is it a waste of time? Again... Thanks for everyone's input and help. I really appreciate it.

George You are very perceptive. The existing guidance requires the radon fan and all piping above it to be in unconditioned space (which also should be ventilated space) . New homes are now being built with conditioned attics and insulation in the rafters. Just as no one would put a radon fan inside a cathedral ceiling home the guidance does not allow the radon fan to be installed in your conditioned attic. Maybe other members on this forum could give an answer of how to deal with this and be within code.
One solution as you mentioned is to create an unconditioned space in the attic for the fan and piping. I would recommend it also be ventilated space. It would need an access door to be able to install and repair the fan. And it would need to be have an electrical power source and large enough to house the fan. Good luck with your new home. Sounds like you are considering every detail.

Hi George. I am a certified building scientist and radon professional and I like your plans for your house. I have foam board under my house which meets LEED gold standard and my radon was still elevated. An active system lowered it nicely.

If you are doing 2" of foam board plus 10-20 mil poly tape sealed under-slab (which is a ton of work by the way) consider using 2" minimal of 2lb closed cell spray foam instead.

The sprayfoam underslab will be a single application insulation, vapour barrier and air/radon barrier. The material cost per square is a bit more but the sheet insulation and poly method will have significant labour costs. We find the reduced labour cost of sprayfoam installation more than offsets the increase in material cost.

What is important to realize is that the lions share of radon entry is by mass transport (i.e. air/soil gas leakage from holes, cracks, missed seals etc.) and not diffusion. Typical construction and even super duper great construction lack the sealing detail and workmanship to make a perfect or even good seal. I have seen thicker membranes, like the 10 to 20 mil poly you plan to use, placed under slab and the increased thickness of the make the sealing details at penetrations and corners very difficult as the material bunches up. This increases the chance for leakage. Expanding sprayfoam on the other hand makes as close to a perfect seal as humanly possible. This great seal will mean that you can use a smaller radon fan to get better pressure field extension or in other words, less energy & better radon control.

Some brands of 2lb closed cell have been tested as a radon barrier and it out performs poly for radon diffusion by at least 4 times and potentially up to 50 times depending on thicknesses of poly and foam. If I had it to do over again I would have put spray foam under my slab but this was not a builder option. In Canada a government approved method has been developed for sprayfoam radon barriers underslab. See the attached documents and link below. The radon specification is the 5th download listed.

https://www.cufca.ca/document_library.php

Hello, George
In addition to what Larainne and others have written, I want to emphasize some things in response to a premise at your original inquiry

Macon, NC where according to the EPA the radon levels are between 2.0-3.9%pCi — George

1) The units of concentration of radioactive material per volume, picoCuries per liter (here, of radon in air) are admittedly an unfamiliar thing to most. Although the abbreviation "pCi/L" does bear a little similarity to "pct." or "percent", it actually has nothing to do with percentages. Unfortunately, this can be a source of confusion. The numbers on the EPA Zone maps are not percentages.
2) Another important thing to understand is that the EPA Zone Map does not say that radon levels are within certain ranges, only that--based on the preliminary information available at the time the maps were constructed (nearly three decades ago)--the predicted countywide average screening level in the lowest livable area of the building was expected to be in the given range. Therefore, it must be recognized that radon levels in specific buildings in Macon, NC may be less than 2.0 pCi/L or they may be greater, even in some cases much greater, than 4.0 pCi/L.
3) As Larainne said, the radon maps have emphasized, from the start, that they were not to be used to decide whether to test. Their purpose was only to help decision-makers allocate limited resources in a manner likelier to have more benefit.
4) Also, from the start, EPA clearly recognized the preliminary nature of the maps and encouraged the development of better information over time.

Thanks for all the information everyone. It's very helpful.

Ok so tell me if this sounds like a sound idea: I will put sump pump and radon tube in same well hole. Run radon tube up and over to the Rim joist facing the garage and pop out into the garage. Then turn up and build a small closet in the corner of my garage to house the fan unit and electrical for the fan unit, then make a single pipe or 2 run up through garage roof and outside. Since the garage is not a living space it should be ok. I will also include a small fan unit on the side of the house to draw air out of the closet space and vent outside in case fan unit or fittings leak in closet area. Let me know your thoughts.

George, can you put the fan in the garage attic or is their living space above the garage? If the garage attic is conditioned you could build your fan closet in the attic without taking room out of the garage.
We have convinced many builders in our area to put a "T" in the draintile pipe before it enters the sump pit. A 4" PVC DWV pipe is extended through the floor for future radon use if needed. You still need a sealed lid for the sump pit but having the radon pipe seperate makes it a little easier to work on the sump pump.
Also that pipe can be extended through the floor anywhere and you may have ia location that makes more sense for the radon piping than where the sump pit is located.
About 60% of our mitigations go from a sump pit, into the garage and up through the garage attic and roof with the fan in the attic. I would suggest using 4"pipe for everything. We have had to abandon some plumber installed systems that used 3" pipe because we could not move enough air no matter what fan or combination of fans we tried.

The garage cieling sits well over 13ft off the floor and I do not have direct attic access. I am not worried about losing a 1ft-1-1/2ft of space in my garage in order to make it easier on me or a tech to come change out a fan if the need ever arises. The garage will not be conditioned space like the house but as an ex brinks home security installer I can tell you I hated climbing in attics to fix or run stuff. Good info about using 4" pipe for install. I like the sump pump / radon combo as it looks a lot cleaner than two separate holes ( although sealed ) and with one hole verses two it's less of a chance for a missed seal leak.

Be sure and use ferncos in the pipes just above your sump pit cover so you can easily get into your sump pit for pump maintenance. Drill a small hole in the cover to allow you to run mason line attached to your pump float to allow you to periodically check your pump is still good.

I wouldn’t put the rubber coupler right above the sump. Maybe bump it up to about 2 feet. That way if you can also use the pipe as a means of putting water in the sump to test it without breaking the seal if you ever want to. Also, since you’re going to have your nice hole saw out, cut and additional 4 and a half inch hole in the lid. Then cover that with a piece of lexan. That way you can keep an eye on the water level without having to take off the lid. One last thing. I highly suggest using duct tape to bridge the gap between the lid and the bucket first. Those lids rarely fit the buckets the way they’re supposed to. So if you put duct tape around the perimeter first, then cover it with polyurethane caulk, when (not if) you need to get in there again, you can just score the seal and the duct tape rips up kind of like a zipper. Much easier access rather than just filling that quarter inch gap with caulk. Good luck!

When you slid the fernco up you will still have a stub to pour water into. No need to have the cover up 2 feet to get it out of your way. And if you use the mason line technique there would no reason to remove the cover to check the pump.

George, you have been responsible for a ton of great information flying around from all over North America. I think we all agree you are on the right track, but I just wanted to point out one possible consideration of using the sump as your extraction point. They say the average life of a sump pump is 5 to 7 years. Depending on the circumstances the sump crock should be cleaned regularly to ensure continued operation. Every time you open that puppy up, you've got to ensure you are sealing it up completely, again.
I'm a big fan of Robert's idea of putting a "T" in the drain line next to the sump crock and running your 4" radon vent up to the rim joist and out to the garage. (That radon pipe is only going to be 10 or 12 inches away from where it would rise up from the sump cover.) With a properly sized fan, mounted in the garage, and 4" pipe I would think you would easily get 15 to 20 years of life out of the radon fan. By doing that you are not disrupting the radon mitigation system whenever you want/need to service or change the sump pump. Just another thought!

Great advice from everyone. Several years ago I ordered a crawlspace sump pit which is shorter that the typical pit used in our area. It came with a lid that had a hole for the electrical cord or cords and a rubber grommet for that hole. It also had two 3 1/2" holes with a variety of rubber seals for 1 1/4 through 2 " pipe plus two solid rubber seals to be used if there was no pump installed. I discovered this was a perfect replacement in existing sump pits that had an open slot or other non airtight lids. We drill a 4 1/2" hole for the radon pipe. We clean the lip on the sump pit where the lid sits and apply weather stripping to it for the airtight seal. Often smoke tests show no leaks but we usually screw the lid down with 4 small deck or stainless steel screws. Occasionally silicon caulk is needed to help seal the perimeter but usually the weather stripping is all that is needed which makes it easily removable.
We put the second 3 1/2" rubber seal in the hole that isn't needed for the sump pump pipe. This seal easily pops in and out and serves as an inspection hole and access to reach in and manipulate the float or use a shop vac to clean sediment.
I don't want to push a particular supplier or manufacture on this site and the supplier I get them from does not list the lids separately from the pits. They special order the lids dropped shipped from the factory to me.

Good afternoon- couple of thoughts This feels like the old list serve with everyone chiming in to help. thank you George for posting this, turned into a really good discussion.
1/ as a plumber who is a radon mitigator i never/ amost never (i have once in 15 years ) use sump lid as my connection point. When you need to get sump lid off in a hurry during a flood they never shut the radon fan off and it can cause back-drafting and carbon monoxide poisoning. Should have known better will not replace Dad or kids..... i know it is allowed but most of my work is caused by builders or site trades not adequately following building code. I will not risk contributing to someones demise because they did not read my nice label on sump lid in an emergency situation.
2/ as a sump lid seal we use a Dow caulking called draft attack (i think in USA it is called seal and peel) it is a removable caulking work great as long as you don't put it between lid and sump. We use sheet lexan that we have supplier cut into 2' x4' sheets for us. get two sump lids out of a sheet and cost are significantly lower than buying sump lid covers. We custom cut it to fit. Always place a warning label.
(we tape the empty caulking tube to sump discharge pipe so they know what they have to go buy to reseal sump lid)
3/ We cut an hand hole into lid with a 4" hole saw and use a 4 inch PVC test plug that drops in and does not need to be caulked in.
4/ if you are going to penetrate the fire wall in the garage, in Canada most have a 1 hr fire rating you may want to install a fire collar on the pipe (not required under Ontario building code ) but we always mention it and customer usually buys it. it is really important to make sure that the opening is sealed (don't want car exhaust to go into basement) and we usually use a fire rated caulking.

Hi George. you said you "will also include a small fan unit on the side of the house to draw air out of the closet space and vent outside in case fan unit or fittings leak in closet area". I am not sure this is necessary or even a good idea unless it is required in your area. An unoccupied attic should be well vented anyway. I think a set of passive vents in the closet (one at the top and one at the bottom) or additional passive venting of the attic (still meet your local code requirements though) is better. Typical breezes and sun on a roof result in a significant amount of venting and should dilute any small to moderate radon leak (plus there is no one occupying the attic). Adding a powered fan to an enclosed structure that is not fully designed for it can do all kinds of funny things with heat and humidity that can cause a bunch of other issues (rot, freezing, condensation etc.). My fan sits in my garage and I have had no issues, of course Bob Wood installed it so the thing is mounted for gale force winds :). Bob does great work!

I have seen where the sump pit set in front of the Draw pipe for the radon. Basically they had a 4" pipe going right through the concrete pad and then about 8-12" away was the sump pump pit with a sealed lid. I had thought about that as well. As mentioned above after posting the previous info I was searching the web for install pictures and came across the one I described above. And after reading yours and Davids posts back to me I think that is the better install option. And not sure if NC requires it or not, but more than likely will, I will impress upon my installer what I would like to have and see what we thinks and come to some kind of agreement. After all at the end of the day I have to look at it for the next 30-40 years and he has to be able to make it fit code and testing. I have seen in a few houses here in America when I was an alarm installer where they used Plexi or Lexan caulked and screwed right to the cement floor to seal sump pit.
Yeah I was just planing like a really tall closet space from floor to ceiling in the garage and just have just the tube pass through the garage roof area, this way the fan would just draw what was in the closet not the attic as well. No sense in bringing down that OVERLY hot North Carolina garage attic heat into the garage.lol..But good points and I am sure I will change my mind by then about it.