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.