How Radon Mitigation Works (Different Types Of Radon Mitigation Systems)

Date Published: September 11, 2023

It’s official – the CO Senate Bill 23-206 Radon Law is now in effect. This new law has been implemented to increase radon awareness and safety during real estate transactions. We predict that it will most likely lead to increased radon testing, and thus an increase in radon mitigation.

To read more about CO Senate Bill 23-206, check out our article, “How Will the CO Senate Bill 23-206 Radon Law Affect Me?”

At Scott Home Inspection, a division of Scott Home Services, one of the primary services we offer is radon testing. So it follows that, when radon levels are high, we we will always recommend radon mitigation in the home. Many of our clients are curious about the what radon mitigation is and how it works. Therefore, we thought it’d be a great topic to explore in this week’s article!

What Is Radon Mitigation?

Radon is a radioactive gas that emits naturally from the earth’s crust. Prolonged exposure to high concentrations can lead to detrimental health issues. So you DO NOT want this stuff in your house. (For more about radon gas, click here.) How do we get it out?

That is where radon mitigation comes in. Radon mitigation is the practice of reducing the radon levels within a building. A specialized system must be installed in the building in order to reduce radon levels to less than the EPA-recommended limit, 4.0 picocuries per liter (pCi/L). Colorado is known to have high concentrations of radon state-wide, making radon mitigation a necessity in many homes. That’s why some counties even require new builds to be radon resistant.

Active radon mitigation system

An active radon mitigation system.

Exploring Radon Mitigation Systems

When it comes to mitigating radon, there are two primary types of systems – active and passive. Active systems utilize a fan that pulls air out of the home and expels it to the outside. On the contrary, passive systems do not have a fan and instead use natural pressure to pull radon out of the home.

There are several variations of both systems, and the most suitable type of system is dependent on the type of home you have. It essentially all depends on the foundation of the home, which can be one of three varieties – basement, slab-on-grade, and crawlspace (shown below).

Different types of foundations for radon mitigation

(From left to right) Basement, slab-on-grade, crawlspace. Image sourced from:

Subslab Suction

Active subslab suction is the most widely used technique. These systems are installed in basements and slab-on-grade foundations. It involves inserting a pipe through the slab and into the gravel or dirt beneath the slab. When the fan is activated, it will create suction that will pull the radon from the soil and out of the house. When installed correctly, this technique is generally very effective.

Passive subslab suction is another option. This involves the same process as active subslab suction, minus the powered fan. Many new builds will have passive subslab systems installed. But keep in mind that just because a system has been installed, it does not necessarily ensure sufficient radon mitigation. That’s why getting a radon test is so important. In many cases, a fan will need to be added to a passive system in order to increase its effectiveness.

Sump Hole Suction

As suggested in its name, sump hole suction is the process of installing the mitigation piping into the sump pit, and subsequently sealing off the pit to make it air tight. This technique is used in homes with basement foundations that, of course, have a sump pit. With this type of system, radon gas is drawn into the sump pit and then pulled out of the home. There is a level of convenience with this option being that the sump pit is already present in most basements. Similar to subslab suction, you can also utilize passive or active systems for this technique.

Sump Hole Suction. Image sourced from:

Sub-membrane Suction

Sub-membrane suction is the the main technique used for homes with crawlspaces. This involves utilizing a large, (preferably) continuous vapor barrier over the entirety of the crawlspace. A pipe is then passed through the barrier and out to the exterior of the house. When done properly, sub-membrane suction is said to be the most effective radon mitigation method. This method is also suitable for passive and active systems.

Sub membrane suction radon mitigation technique

Sub-membrane Suction. Image sourced from:

Crawlspace Ventilation

Certain ventilation techniques can also prove to mitigate radon. Vents on the crawlspace to the outside can help to create a natural pressure differential that pulls the air out of the home. Additionally, allowing the the free flow of air can help to dilute any radon gas that may be within the foundation. This too can be active or passive. Active ventilation would use the aid of a fan to create airflow, while passive does not. While this technique could prove to be effective, it could also cause an increase in energy costs. Additionally any pipes, fixtures, or appliances in the crawlspace would need to be insulated from the cold.

Radon Mitigation System Installation

When it comes to mitigating radon, there are several different routes you can take. As mentioned above, the EPA states that radon levels that are greater than or equal to 4.0 picocuries/liter are hazardous and should be mitigated. So if your radon test results are high, it is best to consult with a NRPP-certified radon mitigation specialist.  They can assess your property to determine the optimal plan of action.

Note: Depending on the size and/or configuration of a home, one pipe may not be sufficient. Sometimes additional pipes must be installed in order to successfully reduce radon to a safe level – especially in very large homes. And even in some rare cases with homes that have foundation combinations – such as a house that has a partial basement and partial crawlspace – it may be necessary to install two different styles of systems!

Testing For Radon

It is our mission to help Colorado residents live in safe, healthy, and comfortable homes. And that’s why we have built a team of NRPP-certified experts dedicated to testing for harmful radon levels. Even if you have a functioning radon mitigation system, the EPA recommends periodic testing every two years, as radon levels can fluctuate over time.

If you are in need of radon testing on your property, you can visit us online to learn more, or contact us to book your service today!

Radon testing device

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About the Author: Chris Kimmel

Chris Kimmel worked as an Associate Home Inspector for two years, handling numerous services including sewer scope inspections, pest inspections, mold air sample testing, radon testing, and water quality testing. Chris now works with Scott Home Inspection as a Content Writing Specialist.

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