When it comes to radon, levels in the home peak during the winter season. Please correct me if I’m wrong, but I think it’s mainly because all the windows are closed and if it’s a tightly built house, it gets pulled into a vacuum with the exhaust fans, fossil fuel burning sources, and the chimney effect. The closed up house is literally is creating the low pressure that mitigation systems provide. How much of the radon levels can be mitigated by simply providing make-up air in the house? Crack a window or install a damper in the basement to allow air to enter. The air quality in general would improve as well. Trying to learn so that I can speak intelligently about it.
Radon levels are going to be seasonal as you stated. Best to inform the client as such and suggest seasonal monitoring. Best monitoring should be every seasonal change.
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Seasons, barometric pressure, ground water, open/closed house conditions, ETC can affect levels.
A few years ago, I performed home inspections and radon testing for three duplexes. All three of the duplexes were on the same block and had the same footprints.
There was no consistency in the levels. Even attached units were different. Some were above action level, and some were in the low 1’s.
The only thing that makes sense about radon is that it does not make sense.
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Open the basement windows all winter long and it probably will help reduce radon. Your heating bill will increase. If you’re a HI, don’t recommend any solution other than having a mitigation system installed by a qualified contractor. My recommendation is the same… radon is the #1 cause of lung cancer for non-smokers. Do you want to take that chance with the lives of you and your family? #2 cause of lung cancer for non-smokers is living with secondary smoke. With that logic, you should not mind having someone living in your house and smoking… right??
I’ve had similar results. The only way to know if there is high radon is by testing.
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Chimney effect (low pressure in basement or at lower levels) is a big contributor to higher radon levels in winter. Another big contributor is that the radon levels are naturally higher in the ground during winter in areas where the ground freezes or where there is significant snow cover. Both of these reduce the amount of radon that can escape the ground into the atmosphere, resulting in higher concentrations of radon in the ground.
Radon testing here is right at 10% of the cost of a mitigation system. My advice to anyone that is concerned about radon in their home is to forego testing and just put that money into a mitigation system. Most are still willing to pay for testing as it can force the seller into negotiating the install.
The major cost of mitigation is encapsulation, especially crawlspaces. I know of a system that is costing the buyer over $8,000. Unfortunately, they believed the seller’s home testing device and whatever the seller and realtor said. Straight forward mitigation systems here start around $3000.
I live in God’s Country where it’s about 95% full concrete basements.
The only way that question can be answered is by testing under the exact same conditions, every time. Those conditions would include but are not limited to how tight the house is, the operation of exhaust fans, running a clothes dryer and of course weather conditions, and that’s just to name a few. There are many different conditions and parameters that can affect Radon levels in a house at any time.
Here’s what AI has to say.
Providing make-up air through ventilation is generally considered a temporary or supplemental strategy and is rarely enough to fix high radon levels on its own. While it can dilute indoor radon concentrations, it does not stop the gas from entering your home from the soil.
Effectiveness of Ventilation Strategies
Mechanical Ventilation (ERVs/HRVs): Energy Recovery Ventilators (ERVs) or Heat Recovery Ventilators (HRVs) can reduce radon levels by 50% to 75% in some cases. They are most effective in airtight houses with relatively low initial radon levels (below 20 pCi/L).
Natural Ventilation: Simply opening windows or using fans can reduce levels by 0% to 50%, but this is highly dependent on weather, seasonal pressure changes, and home layout.
Basement Pressurization: Supplying fresh make-up air to a basement to create positive pressure can help minimize the flow of radon from the soil into the living space.
Why Make-Up Air Isn’t a Total Solution
Inconsistent Results: Radon levels often rise again as soon as the ventilation stops or environmental conditions change (e.g., ground freezing or heavy rain).
Energy Costs: Constantly bringing in and conditioning (heating or cooling) outside air can significantly increase energy bills compared to a dedicated mitigation system.
Does Not Address the Source: Professional systems like Active Soil Depressurization (ASD) are much more effective (typically 90%–99% reduction) because they remove radon from under the foundation before it ever enters the building.
Here’s a a good document about Radon.
Home Buyer’s and Seller’s Guide to Radon
Lots of good and true info here…. one important thing to remember is that a 48-hour real estate test sucks. Statistically totally irrelevant but the best one can do when buying a house.
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And that is partly due to the inspector/tester!
A Radon test for Real Estate Transactions is not a “48-hour test”… in actually it is a “48 to 96-hour test”!
I constantly read on this MB about Radon tests being scheduled for the (Minimum) 48-hours, and tons of questions asking for advice on how this is normally scheduled (including the 12-hour pre-test requirement). Some of the advice is astounding!
IMO, if you aren’t scheduling (in most cases) for a minimum of 60 hours duration run time, you are performing as an amateur hobbyist, and should lose your license… if you even have one to begin with!
When I was still offering Radon Testing, I pushed my end-time requirement as close to that 96-hour window as possible! Considering my scheduling was typically 3 to 5 days out, it was a simple thing to place the testing device as soon as the appointment was confirmed, and was ‘picked-up’ at the start of the inspection. Easy-Peasy!
JMHO!
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The problem is, once it has entered home then it can be inhaled. Venting the area and adding fresh air may reduce exposure or dilute the gas. But there is a better way: remove the gas before it enters the living space. It is affordable and proven successful.
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OR… it may increase the introduction of gas within the home!
Atmospheric Pressure has two effects upon a homes interior pressure… Positive and Negative, and then add the phenomenon of 'Stack effect" with it’s varied directions influenced by pressure… and (you can see where I’m going with all this)!
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The answer is very little to none. I have done many radon tests with available “make-up air.” I’ve gotten readings in the 30s in 90-year-old houses that were so drafty that the walls might as well be Swiss cheese. I have had sellers try to fool the instruments by opening windows, but the averaged radon level was still above 4.
The factors that contribute to radon levels in a structure are so varied and variable that if the building sits where there is a source of radon, the only way to know if it has radon is to test.
If you create sufficient ventilation, you can get the radon level to near background, but life would be similar to living under a tarp in the yard.
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You do realize nobody really opens their windows regardless of the season.
Adding even more fuel to your (good) point is that the EPA average for the tests my Sun Nuclear 1028 & 1030s is really only 44 hours. The first 4 hours are chopped off of the “EPA Average” since they figure the machine needs to acclimate to it’s testing environment.
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I have said this elsewhere in other threads, but the result of the 48-hour Real Estate Purchase Protocol test on my house was 7.5pCi/l. The EPA (NRPP and AARST) says that the most accurate test is a 12-month test. I bought an alpha track test from Amazon and placed it for 12-months. Result…2.8pCi/l. The tests have very different protocols as all of you know. Since I did more research into this than I can believe when I put together a 16-hour radon course for InterNACHI (it got shelved when Covid hit and there’s no plan to activate it), I can knowledgeably tell you that my result is common everywhere.
Long Term Alpha Track Radon Detector Kit (Can NOT Sell to New Jersey Addresses) - Household Alarms And Detectors - Amazon.com
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I have a window that has been open about 1” all winter. The reason is that my house is so tight that air is being pulled from between the window sashes and condensate forms between them. If I leave a window open, it doesn’t happen. That implies to me that I have significant negative pressure in my own house and that could be increasing the likeliness of radon traveling the path of least resistance to my house. This is the core of my question. Just a theory, once I buy the radon monitor, I’ll check to see if this is actually true.
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