Radon mitigation effects on stove

SD Golden

New Member
Aug 1, 2018
44
South Dakota
Hey guys, early this summer I tested my home for radon and results showed high levels in the basement bedrooms. I installed a radon mitigation system on my sump basin because of this. However, I found when the fan is on, I can notice a smoky campfire smell in my basement (stove is not burning, it's 79° out). The sump basin is sealed, but I assume I'm pulling a negative pressure on the whole basement somehow with the radon fan as this has never been the case with the stove in the off season. I'm worried I'm going to run into draft issues when burning season gets here if I run both, but I don't want to be pulling radon into the living space via the stove if I turn the fan off. Has anyone had experience with addressing these issues or have any suggestions? I should mention that the stove is below grade (split level) so a fresh air kit for the stove is out of the question.
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,132
South Puget Sound, WA
It does sound like a negative draft situation. Not sure how much that will improve as the temps drop. There has been some past discussion on this. It can be a problem. Search on 'radon'.
https://www.hearth.com/talk/threads/persistent-downdraft-issues.174717/#post-2348684

You may need to feed the stove outside air, which gets a little complicated if this is a below grade basement because one shouldn't connect outside air where the inlet is above the stove. However, some stoves don't directly feed the outside air to the primary and secondary intakes. What stove make and model is this for?
 

SD Golden

New Member
Aug 1, 2018
44
South Dakota
It does sound like a negative draft situation. Not sure how much that will improve as the temps drop. There has been some past discussion on this. It can be a problem. Search on 'radon'.
https://www.hearth.com/talk/threads/persistent-downdraft-issues.174717/#post-2348684

You may need to feed the stove outside air, which gets a little complicated if this is a below grade basement because one shouldn't connect outside air where the inlet is above the stove. However, some stoves don't directly feed the outside air to the primary and secondary intakes. What stove make and model is this for?

The stove is a Blaze King Sirrocco 30
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,132
South Puget Sound, WA
The stove is a Blaze King Sirrocco 30
That could make for a touchy situation. The stove needs adequate draft to perform correctly.
 

Highbeam

Minister of Fire
Dec 28, 2006
16,105
Mt. Rainier Foothills, WA
And even with a direct outside air connection, you could still get reverse flow when the door is open for lighting or reloading.

Can you reduce the flow rate of the radon blower?
 

SD Golden

New Member
Aug 1, 2018
44
South Dakota
And even with a direct outside air connection, you could still get reverse flow when the door is open for lighting or reloading.

Can you reduce the flow rate of the radon blower?

I am unable to slow the fan down, it's simoly on or off. But, if I ran a smaller diameter pipe from the sump pit to the fan I could reduce it down, but finding the right balance will be tricky.
 

WinterinWI

Member
Dec 6, 2018
89
Wisconsin
I've always heard radon is more prevalent in winter because the house is closed up, as opposed to summer when windows are likely open and constantly exchanging airflow. Since your stove doesn't have an oak, it would be exchanging the inside air to some degree. It may dilute radon to acceptable levels.

They make radon detectors, not sure how accurate they are. You could get one, run it for awhile to establish a baseline, then when heating season kicks in, turn off the radon fan, fire up the stove and see what happens.
 

spudman99

Member
Jan 26, 2018
123
Yardley, PA
Turn off the fan during the winter. Radon is a very slow particle that takes a long time and in much higher concentrations to cause negative health impacts. There are some studies that suggest radon exposure can mitigate or reduce risks of lung cancer. Either way harmful effects are from repeated exposure. I see you have basement bedrooms. If they are occupied full time (assuming a colonial home and not a split level), perhaps introduce some fresh air into the bedrooms, or during the winter months ensure that there is air flow. Radon pools in stagnant air, this can be offset by moving air around the lower level, thereby introducing fresh air. This will reduce the concentration of Radon to offset any potential impact.

Think about the radon test. One must close all windows and doors for the test period for the test to be valid. Leaving 1 window open will negate the test. It does not take much in the way of fresh air to make it safe to breath. Sorry but I cannot help with the negative pressure issue as I am not that skilled with stove operations.
 

peakbagger

Minister of Fire
Jul 11, 2008
4,610
Northern NH
A few things to think about. Radon is heavier than air that's why it builds up in a basement. The house is inherently negative to the outdoors and that draws radon up from the ground if its present. The other source of radon is water from usually deep wells. That arguably is far more dangerous than soil radon as the radon comes out of the water when its pressure drops especially when its heated which is usually a shower head or sink so you are breathing in the radon directly out of the shower head. It also diffuses out in the air and then eventually sinks to the basement. Subslab ventilation creates a negative draft under the slab and unless its sealed perfectly also makes a dent in the radon on top of the slab. If you have radon in the water, the way to fix it is with an air scrubber on the incoming water line. The water is sprayed out in sealed tank and fresh air if used to sweep the radon that is released up and out of the house which unfortunately depressurizes the house and causes more radon to potentially leak into the house from under the slab meaning the need for subslab ventilation.

The standard radon test done for house sales is just sampling in the basement and frequently no sampling of the water. Unfortunately it frequently comes up during a house sale and both parties just want it to go away quickly so it opens up business opportunity to sell a high priced product to a very motivated buyer with little comparison shopping. Reportedly some real estate agents get a referral fee from radon mitigation contractors when they steer business to the contractor. This is further worsened by states that pass radon licensing laws so that only a license contractor can sell and service these systems. This keeps the con artists out of the system but it also tends to raise costs significantly. I have seem a few radon mitigation bills where standard products are marked up 200% to 400%.

I am not saying that high radon levels are a con and they do need to be dealt with but if the pressure of house sale is taken away, the actual solutions can be lower cost although it does require up front testing. First thing is figure out where the radon is coming from. If its in the water deal with that first. Depending on the level, activated carbon filters on the water used in the interior of the house (no sense in treating hose water) will work. Its less costly than the air scrubbers but the filters need to be changed out every year or so and the used filters may be special waste in some areas. A contractor may need to dispose them as low grade radioactive waste but most homeowners can just throw them away. The air wash systems can be bought direct from some manufacturers and installed by a competent homeowner for considerable savings. The big cost is you need to pump the water up to pressure twice, once from the well and again after the air wash unit. As like with the carbon filters, don't treat water used outside the house.

If the radon is from the ground, its going to tend to stay in the basement. Most people do not sleep in the basement so its worth taking samples in the actual living space and the basement so see if the numbers are less in the living space. If the living space reads lower than the limits you may not need continuous subslab fans, you may be able to get away with a timer on the fans and then retest. If the stove is in the basement, think what its doing, its pulling cool air usually from the floor into the stove and venting it up the chimney. Its effectively acting as a radon removal device from the basement. So it may be that your stove can act as radon removal device except that its fighting with the radon removal fans. I have a friend with a old granite block farmhouse basement that had a radon issue. He made a substantial difference by running a duct off his barometric damper on his oil boiler and running it down to the floor. He has a separate flue with a wood stove that keeps his chimney hot so he always has a draft on the oil flue. If the burner is not running, the air tends to leak in via the barometric damper and pulls air in from the floor. His radon levels dropped to below the action limits and stayed that way with this minor modification.

My guess would be to turn the subslab fans off during stove operation at minimum. The other thing to consider is if you have tight house is put in air to air heat exchanger to drop the pressure differential between the outside and inside.
 
Last edited:

snaple4

Member
Dec 18, 2017
107
AR
Hey guys, early this summer I tested my home for radon and results showed high levels in the basement bedrooms. I'm worried I'm going to run into draft issues when burning season gets here if I run both, but I don't want to be pulling radon into the living space via the stove if I turn the fan off.
our company is capable of installing radon equipment. We avoid doing them. To do it correctly you actually need to perform a few tests (blower door for instance) to properly size the fan. Also, sealing up any and all cracks that you can find in the wall/floor.

Few questions:

Did you do this yourself?
Did you air seal the slab and walls?
Is the sump pump cover air tight?
What calculation was done to size your motor?
What size pipe and distance do you have for the negative and positive pipes?
How does the positive pipe exist the building?
What static pressures do you have in the positive and negative pipe?
 

tadmaz

Member
Dec 21, 2017
243
Erin, WI
Thanks for the thread, I may try turning off my radon fan and see if the stove behaves differently to satisfy curiosity. My stove is upstairs though. My radon level in the basement was 68, and the safe level is 4. Is your stove in your basement?
 

BIGChrisNH

Feeling the Heat
Dec 16, 2015
364
New Hampshire
My stove is also below grade, and I too have a radon mitigation system, the fan has been running consistently for years and I have not noticed any problems with running my stove with the fan running. That said, my basement is divided in half, the finished half having the stove and hearth, the unfinished half with the oil burner, water heater and radon system. I never even thought about it having an effect either way, this is an interesting topic though.
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,132
South Puget Sound, WA
Every house is different. The OP indicates concerns with negative pressure as indicated by the smoke smell since the radon fan has been running. However, my guess is that this is with some upstairs windows open. If so, that may be accentuating the negative pressure effect. Time will tell as temperatures outside get cooler and upstairs windows and attic fan vents, etc. get closed up. If draft remains negative in the basement when temps drop below say 45º, then I would try opening a basement window an inch. If that solves the problem then peakbagger's suggestion of an HRV may be the best solution.
 

m159267

Burning Hunk
Mar 12, 2009
192
East-Central MO
We have had a radon mitigation system installed for 3 years. There is a pellet stove in the basement with an oak and a high efficiency fireplace upstairs in the family room - also with an oak.There have been 0 issues with either. When I open the pellet stove door to scrape the burn pot (still burning) there is no issue. Likewise when adding wood to the fireplace - no problems.
Our radon levels were pretty high - 12-13 in the basement and oddly enough higher upstairs on the main level.
Since adding the mitigation system our long term basement level is now in the area of 0.4.
I use an Air Things Home Radon Detector (ordered from Amazon) to continually monitor. In fact I used the detector to determine I had a radon issue.
The official testing confirmed the accuracy of the detector.
There is some speculation that radon is not really a problem. Regardless, we had the mitigation done because if/when we go to sell it would have to be done anyway.
 

snaple4

Member
Dec 18, 2017
107
AR
Every house is different. The OP indicates concerns with negative pressure as indicated by the smoke smell since the radon fan has been running. However, my guess is that this is with some upstairs windows open. If so, that may be accentuating the negative pressure effect. Time will tell as temperatures outside get cooler and upstairs windows and attic fan vents, etc. get closed up. If draft remains negative in the basement when temps drop below say 45º, then I would try opening a basement window an inch. If that solves the problem then peakbagger's suggestion of an HRV may be the best solution.
An improperly designed/installed radon system will cause unacceptable levels of negative pressure within the living space. It can also decrease comfort and increase heating/cooling bills. Making sure radon system is correct before spending more money on expensive equipment to fix a problem that might be caused by the radon system is what I would recommend.


We have had a radon mitigation system installed for 3 years. There is a pellet stove in the basement with an oak and a high efficiency fireplace upstairs in the family room - also with an oak.There have been 0 issues with either. When I open the pellet stove door to scrape the burn pot (still burning) there is no issue. Likewise when adding wood to the fireplace - no problems.
Our radon levels were pretty high - 12-13 in the basement and oddly enough higher upstairs on the main level.
Since adding the mitigation system our long term basement level is now in the area of 0.4.
I use an Air Things Home Radon Detector (ordered from Amazon) to continually monitor. In fact I used the detector to determine I had a radon issue.
The official testing confirmed the accuracy of the detector.
There is some speculation that radon is not really a problem. Regardless, we had the mitigation done because if/when we go to sell it would have to be done anyway.
I have a copy somewhere but studies have shown that constant air movement (such as a ceiling fan) causes the radon to hit again items rendering it harmless. I’m not saying radon isn’t an issue, because I think it can be, but I think there are viable ways to work with lower levels (under 100).
 

jetsam

Minister of Fire
Dec 12, 2015
4,163
Long Island, NY
youtu.be
Let the fan ventilate the basement in the summer, and let the stove ventilate the basement in the winter. The stove is sucking air out of the basement and shooting it up the flue when it's burning. If radon levels get higher, run the fan for a while.
 

SD Golden

New Member
Aug 1, 2018
44
South Dakota
Thanks for the replies. This winter, I may try turning off the fan while lighting the stove until the flue gets warmed up and see how it goes. I did install the system myself and the sump lid is sealed with a sheet of lexan anchored to the floor with a foam seal and all pipes and wires pass through rubber grommets.
 

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,472
SEPA
Run another duct from the sump to the oak on the stove, and use the airflow to send the radon up the chimney when burning. Turn the fan off when using the stove, on when the stove is not in use.
 

snaple4

Member
Dec 18, 2017
107
AR
Thanks for the replies. This winter, I may try turning off the fan while lighting the stove until the flue gets warmed up and see how it goes. I did install the system myself and the sump lid is sealed with a sheet of lexan anchored to the floor with a foam seal and all pipes and wires pass through rubber grommets.
If you have enough of a negative pressure with fan on to cause back drafting in summer, what do you think will happen (when stack effect is greater) in the winter and your stove burns down? You may not have any problems this winter, however, it seems to me that you are asking for problems.

As far as sealing, I am talking about plumbing penetrations in the floor and below grade walls, cracks (even minor ones), and possible test holes. It is good that you ran pipe and wires through seals (we have only used tight fitting rubber so I can't say how effective foam is).

If you can answer some questions I can give you an idea if you are in the range of a properly sized radon system.
1) What is the static on your exhaust/supply pipe? You do have a manometer on your pipe right?
2) What size and distance is your pipe (number of elbows as well please)?
3) Can you provide the CFM/Fan chart for you blower?
4) What is the Square footage of each floor?
5) Did you drill any holes in the floor to test for negative pressure under the slab?
 

jetsam

Minister of Fire
Dec 12, 2015
4,163
Long Island, NY
youtu.be
You also have to worry about a carbon monoxide hazard when the stove burns down and the radon fan is on. I would just shut the radon fan down for heating season.