Radon gas anyone?
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RNeumann
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Travelover
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I installed one in my last home. I bought a HF hammer drill and drilled 1/2" holes around the perimeter of a 4" hole on the basement floor. (The hammer drill puked on the last hole, so I replaced it on warranty. :laughing
I used a wet vac to dig a hole about 5 gallons in size under the hole in the concrete floor. I stuck my 4" PVC pipe in the hole and sealed it to the concrete with caulk. I ran the 4" PVC pipe up the wall then into my garage and mounted the blower in the garage rafters with an exit on the far side away from any windows. There is a little manometer that mounts on the pipe just above the pick up point to monitor vacuum. Hardly any air comes out of the discharge - you can hardly feel it on a bare hand.
I used a wet vac to dig a hole about 5 gallons in size under the hole in the concrete floor. I stuck my 4" PVC pipe in the hole and sealed it to the concrete with caulk. I ran the 4" PVC pipe up the wall then into my garage and mounted the blower in the garage rafters with an exit on the far side away from any windows. There is a little manometer that mounts on the pipe just above the pick up point to monitor vacuum. Hardly any air comes out of the discharge - you can hardly feel it on a bare hand.kcflhrc
Veteran Member
Hopefully it vents outside, not into the attic
coldsteelva
Veteran Member
I was thinking the same thing, through the attic is one thing, but INTO the attic is very bad.
RNeumann,
yes my floor has a vapor barrier but I don't see how it helps or hurts with regards to pulling the radon gas out. it's more about having good air flow though loose stone. I used crushed stone with a fair amount of chip and dust. It compacts nicely. If I had used a one size stone such as #5's, 3/4 inch stone, air would flow unrestricted.
I'm an engineer so I'm looking closely how the systems work, or don't work. A simple approach likely works in most situations. I know my layout is unusual with a 30 ft by 30 ft footer system inside a 54 foot by 70 ft footer system. With a suction point with access through the slab, it's 90 feet to the far reaches. let alone the isolated 30 ft by 30 ft area.
Reading detailed plans, even suction can be an issue. For example if a large crack is 1/2 way between the far wall and the suction pit, there can be little to no suction against the wall. Further, there are some references that state caulking along walls prevents a source for the air to allow the Make up air in. All big cracks should be filled otherwise that will be the main draw point.
Theoretically, if a slab has no cracks and is sealed to walls/footers, the fan would not draw any air out. And, the radon would still migrate through the slab.
yes my floor has a vapor barrier but I don't see how it helps or hurts with regards to pulling the radon gas out. it's more about having good air flow though loose stone. I used crushed stone with a fair amount of chip and dust. It compacts nicely. If I had used a one size stone such as #5's, 3/4 inch stone, air would flow unrestricted.
I'm an engineer so I'm looking closely how the systems work, or don't work. A simple approach likely works in most situations. I know my layout is unusual with a 30 ft by 30 ft footer system inside a 54 foot by 70 ft footer system. With a suction point with access through the slab, it's 90 feet to the far reaches. let alone the isolated 30 ft by 30 ft area.
Reading detailed plans, even suction can be an issue. For example if a large crack is 1/2 way between the far wall and the suction pit, there can be little to no suction against the wall. Further, there are some references that state caulking along walls prevents a source for the air to allow the Make up air in. All big cracks should be filled otherwise that will be the main draw point.
Theoretically, if a slab has no cracks and is sealed to walls/footers, the fan would not draw any air out. And, the radon would still migrate through the slab.
RNeumann
Elite Member
So you are a licensed civil PE? Or is it electrical, mechanical rocket etc?
I appreciate that you are reading plans and working on theory. It is the exact same situation we faced a few years back in China. The local “experts” wanted answers as to why the large commercial building’s HVAC couldn’t maintain the environment needed for wine production. When the designer arrived from the USA he found the building construction was substandard and the locals had added huge vents to the outside. Needless to say when the vents were closed and the cracks sealed the HVAC worked fine.
You are experiencing the same thing- the theory is you want to create enough vacuum/negative pressure to overcome the leaks. That’s a difficult thing to overcome.
We typically start with a 4” perf pipe in a 1” stone bed at footing level. The pipe is day-lighted and acts as a drain for any water that may migrate in under footing level (we never see water out of this but we continue to put it in....). The 4” pipe is also turned up and converted to a 2” pipe and vented through the roof of the structure. On top of that we install a true vapor barrier- not just 6mil visqueen- that is sealed to itself at the seams and the stem walls at the perimeter. If (and it’s rare) we are still seeing any radon we can add a fan to pull a slight vacuum. BTW- we’ve never had to seal the day-lighted pipe to create more vacuum so it may not be a vacuum as much as just moving air.
Since it’s too late for most of that I still contend the starting point is to seal everything with a vapor barrier. I realize that sucks to do with interior walls and what I assume is finished space. But with the building sealed from the ground I’m assuming a standard pit, rock and vent system will do just fine. I’ve also seen the perf pipe vent through the roof on both ends. So maybe two pit, rock and vent systems on opposite sides of the basement would help- I’d start with a fan on one side only.
You haven’t mentioned the basement walls. I assume those are waterproofed and sealed. If so, that’s an unlikely source for the radon.
If radon mitigation is thought of as offense and defense the ratio is about 95/5. Defense is the prep and sealing things up and the offense is the fans.
Btw- a lot of radon mitigation is done in crawl spaces with simple building crawl space ventilation. Have you moved the air through the basement to turn it over several times? If testing was done after, it would give you a baseline for the amount and possibly the area the radon was coming from.
I’ve never done an HRV for radon but I’m sure someone has- that may be an option that could help.....
Good luck- I don’t see this as an easy fix. Sometimes good architects and contractors- like engineers- cost a little more up front but save thousands on the back end. It funny how so many people see it as an unneeded expense....some of them even get away with it!
I appreciate that you are reading plans and working on theory. It is the exact same situation we faced a few years back in China. The local “experts” wanted answers as to why the large commercial building’s HVAC couldn’t maintain the environment needed for wine production. When the designer arrived from the USA he found the building construction was substandard and the locals had added huge vents to the outside. Needless to say when the vents were closed and the cracks sealed the HVAC worked fine.
You are experiencing the same thing- the theory is you want to create enough vacuum/negative pressure to overcome the leaks. That’s a difficult thing to overcome.
We typically start with a 4” perf pipe in a 1” stone bed at footing level. The pipe is day-lighted and acts as a drain for any water that may migrate in under footing level (we never see water out of this but we continue to put it in....). The 4” pipe is also turned up and converted to a 2” pipe and vented through the roof of the structure. On top of that we install a true vapor barrier- not just 6mil visqueen- that is sealed to itself at the seams and the stem walls at the perimeter. If (and it’s rare) we are still seeing any radon we can add a fan to pull a slight vacuum. BTW- we’ve never had to seal the day-lighted pipe to create more vacuum so it may not be a vacuum as much as just moving air.
Since it’s too late for most of that I still contend the starting point is to seal everything with a vapor barrier. I realize that sucks to do with interior walls and what I assume is finished space. But with the building sealed from the ground I’m assuming a standard pit, rock and vent system will do just fine. I’ve also seen the perf pipe vent through the roof on both ends. So maybe two pit, rock and vent systems on opposite sides of the basement would help- I’d start with a fan on one side only.
You haven’t mentioned the basement walls. I assume those are waterproofed and sealed. If so, that’s an unlikely source for the radon.
If radon mitigation is thought of as offense and defense the ratio is about 95/5. Defense is the prep and sealing things up and the offense is the fans.
Btw- a lot of radon mitigation is done in crawl spaces with simple building crawl space ventilation. Have you moved the air through the basement to turn it over several times? If testing was done after, it would give you a baseline for the amount and possibly the area the radon was coming from.
I’ve never done an HRV for radon but I’m sure someone has- that may be an option that could help.....
Good luck- I don’t see this as an easy fix. Sometimes good architects and contractors- like engineers- cost a little more up front but save thousands on the back end. It funny how so many people see it as an unneeded expense....some of them even get away with it!
RNeumann,
Purdue Mechanical. Basement walls are sealed poured concrete. I'm confident I'll get the level down. The high measurement we took was 28 and was down in a hole where we have a 7 ft square without a slab. We will be installing the sump/sub slab depressurization and pouring the 7 by 7 slab. I may have to have two sumps to cover both ends. Piping shouldn't be an issue, we have steel bar joists and a chase 7 by 7 from basement to roof.
We have a HRV system but I have read they are not very efficient at removing Radon. Not much better than opening a window. We now use the HRV to pull exhaust from Oxyacetylene jewelers torch. It does happen to be in the basement so when it's running it's clearing both fumes and Radon. They claim the exchange heat, I can tell you the return air from outside is quite cold.
The basement is a walk out with work shops. Doors are opened quite often. My Safety Siren Pro 3 series Radon meter arrived yesterday. So I plan to take measurements in the living space and the basement.
Purdue Mechanical. Basement walls are sealed poured concrete. I'm confident I'll get the level down. The high measurement we took was 28 and was down in a hole where we have a 7 ft square without a slab. We will be installing the sump/sub slab depressurization and pouring the 7 by 7 slab. I may have to have two sumps to cover both ends. Piping shouldn't be an issue, we have steel bar joists and a chase 7 by 7 from basement to roof.
We have a HRV system but I have read they are not very efficient at removing Radon. Not much better than opening a window. We now use the HRV to pull exhaust from Oxyacetylene jewelers torch. It does happen to be in the basement so when it's running it's clearing both fumes and Radon. They claim the exchange heat, I can tell you the return air from outside is quite cold.
The basement is a walk out with work shops. Doors are opened quite often. My Safety Siren Pro 3 series Radon meter arrived yesterday. So I plan to take measurements in the living space and the basement.
ruffdog
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If a person has a woodstove on the 1st floor, would the constant air draw help or make the radon issue worse? House is a 1 story ranch with poured basement?
RNeumann
Elite Member
Well so much for the HRV! Bummer
Hopefully sealing and venting the elevator shaft will knock it down significantly. It sounds like that will be the easiest solution.
I’m not sure how quickly the detector reads (we just use the kits)- 30” or 30 days. But hopefully it’s the former and you can sniff around after a big air exchange and find area/areas with higher levels than others. That would be an easy way to focus efforts.
Hopefully sealing and venting the elevator shaft will knock it down significantly. It sounds like that will be the easiest solution.
I’m not sure how quickly the detector reads (we just use the kits)- 30” or 30 days. But hopefully it’s the former and you can sniff around after a big air exchange and find area/areas with higher levels than others. That would be an easy way to focus efforts.
We record higher and higher radon when we run the wood stove... no experiment records just personal experience!!!
MacLawn
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Does anybody know if having crawl space spray foam insulated will stop radon?
tornadowatchranch
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couple of thoughts and my own experience with putting in my own system
You do not need a big hole saw for the concrete. I used my Harbor freight demo hammer drill with a 3/8 bit. I drilled about 20 holes in a rough circle and used hydraulic cement to seal around the outside.
You can buy a kit at Menards that has some couplings and a fan for about $125.
I got a lot of good info from this site
Do It Yourself Radon Mitigation Help Guide
This site has guides based upon the type of sub slab aggregate you have and other variables. I have sand which is harder to pull than your rock.
I have the same meter and it takes about a day to get a reading but sometimes 3.
My levels vary with the amount of rain we get here in Kansas. I have clay soil and after a period of rain the soil swells which (my theory) prevents if from going around the house so my levels go up.
Install of my system took about 7 hours working alone for 2 slab penetrations.
I have not seen it mentioned yet but the recommended level to mitigate is 4 or above.
You do not need a big hole saw for the concrete. I used my Harbor freight demo hammer drill with a 3/8 bit. I drilled about 20 holes in a rough circle and used hydraulic cement to seal around the outside.
You can buy a kit at Menards that has some couplings and a fan for about $125.
I got a lot of good info from this site
Do It Yourself Radon Mitigation Help Guide
This site has guides based upon the type of sub slab aggregate you have and other variables. I have sand which is harder to pull than your rock.
I have the same meter and it takes about a day to get a reading but sometimes 3.
My levels vary with the amount of rain we get here in Kansas. I have clay soil and after a period of rain the soil swells which (my theory) prevents if from going around the house so my levels go up.
Install of my system took about 7 hours working alone for 2 slab penetrations.
I have not seen it mentioned yet but the recommended level to mitigate is 4 or above.
robstaples
Gold Member
It's difficult to be certain with so many variables ,like how thick of foam, closed cell? , how much pressure build up. But some facts: radon is a big atom 86 protons and 220 weight,
And a half life of 3.8 days.
Compare a balloon of radon with a helium balloon, where helium is weight of 4. The helium diffuses thru a rubber balloon overnight but last several days in a mylar balloon, but with very little pressure differencial in mylar. If you could fill a rubber balloon with no leakage with radon say 1 gal size, it would be half the size or 1/2 gal after 3.8 days. And one quart after another 3.8 days. ( US imperial
)So radon goes away on its own , but you don't want it breaking down in your lungs.
I think your foam , if closed cell and 2+inches, and without cracks, would help significantly, if there is a pressure release for gas build up. Radon bubbles up from a solid - principle uranium and returns to a solid- lead. And a reasonable short life. Half life of uranium is like 4 billion yrs.
I rented a real time meter ( 1 minute) and found my source and mitigated it. Turned my in ground (pad) duct work into radon evacuation header. Works great but lost my force air heating system..
Tornadowatchranch,
I'm lucky my most likely source is an "unpaved" 7 ft sq but also will be where I put my suction after pouring the pad. Unlike most, I have a concrete roof to contend with. If I can get away with one suction point, that will be great. But if I need to add an additional suction on the far side due to shear size, it will be at least a foot from the wall due to our very wide footers.
when we built our all concrete house, I bought the biggest hammer drill I could find. I can drill a 1 inch hole through 8 inch wall in 60 seconds
I'm lucky my most likely source is an "unpaved" 7 ft sq but also will be where I put my suction after pouring the pad. Unlike most, I have a concrete roof to contend with. If I can get away with one suction point, that will be great. But if I need to add an additional suction on the far side due to shear size, it will be at least a foot from the wall due to our very wide footers.
when we built our all concrete house, I bought the biggest hammer drill I could find. I can drill a 1 inch hole through 8 inch wall in 60 seconds
Teg,
I'm not surprised a wood stove would do that. The fire draws a bunch of air making a negative pressure in the house. We piped outside air in to our fireplace and the air would howl out of the pipe! Our wood stove was located in our utility room where the dog door was located. The dog door would swing open a 1/4 in by the air rushing in.
I'm not surprised a wood stove would do that. The fire draws a bunch of air making a negative pressure in the house. We piped outside air in to our fireplace and the air would howl out of the pipe! Our wood stove was located in our utility room where the dog door was located. The dog door would swing open a 1/4 in by the air rushing in.
kcflhrc
Veteran Member
My uneducated guess would be if Radon can penetrate solid concrete then it can most certainly penetrate spray foam
tornadowatchranch
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I forgot to add....My levels started at 25 and went to 16 by just covering the sump and venting that to air outside--no pump at that time. They then went from an average of 16 to 2.5 within a week of adding a system that does NOT draw from sump. My window wells have black pipe from daylight to footer drain so a sump system would really just pull from the closest window well. The only reason I did 2 penetrations was I already had the pipe and it was cheap. If I were to do it again I would likely put in one with a coupling capped to add a second and then follow levels with that meter. If they don't go down enough then add the second. We see a lot of lung cancer in the hospital. Mostly smokers but not all. Makes you wonder!
Good luck with your project. I love projects that have nothing to do with my professional life.
Tornado
Good luck with your project. I love projects that have nothing to do with my professional life.
Tornado
RNeumann,
Do you build houses, or just when you built your own you implemented the under slab tubing? If I understand your system, you are pulling outside air from your perf pipe that exists to daylight? Wouldn't that pull mostly cold air under the slab and limit the negative pressure elsewhere?
What is your though regarding the sump size? For example, in a system that does not have the pre planned tubes. I've seen references where they recommend cutting a hole in the floor and removing 30 gal of soil/gravel. Then sealing the 4 in pipe over the void. I'm not sure how a large pit would perform any differently than a small pit/void
Do you build houses, or just when you built your own you implemented the under slab tubing? If I understand your system, you are pulling outside air from your perf pipe that exists to daylight? Wouldn't that pull mostly cold air under the slab and limit the negative pressure elsewhere?
What is your though regarding the sump size? For example, in a system that does not have the pre planned tubes. I've seen references where they recommend cutting a hole in the floor and removing 30 gal of soil/gravel. Then sealing the 4 in pipe over the void. I'm not sure how a large pit would perform any differently than a small pit/void
prichard
Veteran Member
We are hoping to have foundation built soon. Is there a way to check levels prior to building? Sensor in an upside down bucket?
We are just going to have a crawlspace with dirt floor. Is this only a concern on enclosed basements without ventilation? Is there a strategy if no slab?
We are just going to have a crawlspace with dirt floor. Is this only a concern on enclosed basements without ventilation? Is there a strategy if no slab?
