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What is a Radon Barrier & How Does It Work?


Radon is an odorless gas that can invade your home without you even realizing it. It filters through the cracks in your foundation and flows upwards into your home. Over time, it can cause respiratory issues and is the leading cause of non-smoking lung cancer in the United States. The question is, how can you protect your home from radon?

You can install a radon mitigation system or radon barrier to help divert radon outside your home. Before you decide how to protect your loved ones, you need to understand:

  • How radon enters a home
  • How to lower radon levels
  • What a radon barrier is
  • How a radon barrier works
  • How effective these systems are
  • What a safe level of radon is

Knowledge is power, so arm yourself by learning more below.

How Does Radon Enter a Home?

Radon is an invisible and odorless gas that is linked to lung cancer. This gas is naturally occurring and can seep into your home without warning.

As mentioned previously, it can enter through gaps in the foundation, walls, or floors. Homeowners with foundation issues may have elevated radon levels. Your home doesn't have to be old to be at risk for hazardous radon. The gas is found in the surrounding soil and can just as easily seep into newer homes as it can into older homes. It all depends on how your home and ground react to one another.

How to Lower Radon Levels notes that there are a few different ways to help lower the radon levels in your home, especially if they are below 4 pCi/L. One way is not to smoke inside. Smoking increases your risk for lung cancer because of the chemicals in cigarettes. 

You can also use natural ventilation to temporarily reduce radon levels. Open your windows and use fans to circulate the air. Sealing cracks in the floors and walls will also help you mitigate the flow of radon.

To slow the influx, look at installing a radon barrier or radon mitigation system.

What is a Radon Barrier?

A radon barrier is fitted on the foundation and underneath the concrete slab. It is made from a flexible sheet. If you are concerned with radon in your area, you may consider having a radon barrier installed as you build your new home. High-risk areas are already required to have a radon barrier added at the time of construction.

How Does a Radon Barrier Work?

During construction, workers lay the barrier to keep the concrete slab from making contact with the ground. This ultimately helps to keep radon from seeping into a home. Construction of the barrier begins with a four-inch layer of gravel over the newly dug foundation. The gravel gives gas freedom to move. On top of the stone, workers lay the heavy-duty barrier. The layer keeps gas from permeating the concrete while stopping the concrete from mixing in with the gravel. 

To correctly install a radon barrier during construction, all overlaps should be sealed. Anything that goes through the sheet, like water lines, needs to have a seal around it. Radon barriers work best in tangent with a passive mitigation system, according to the Environmental Protection Agency (EPA). After the barrier is in place, workers install a PVC pipe before pouring the concrete slab. The pipe is typically located in the basement or the sump pump pit. After the slab is poured, a connecting pipeline runs along the wall and through the roof of your home.

The Most Common Types of Mitigation Systems

A radon barrier is installed during the construction of a new property. However, suppose you are experiencing actionable levels of radon in an already finished home. In that case, you’ll want to invest in a mitigation system instead. You can choose between a passive mitigation system or an active mitigation system.

Passive Radon Mitigation System

A passive system uses warm air to push gas from the ground and releases it safely into the atmosphere. However, a passive system does not guarantee that you won't have high radon levels. If you are uncertain about the levels, you need to test the inside air.

An older home can have a passive radon system installed. Adding one requires drilling a small hole, no more than four inches in diameter, through the concrete slab. Instead of going through the home's interior, the PVC pipe runs along the outside wall, extending past the roof.

Active Radon Mitigation System

An active radon mitigation system is the more common option to lower radon levels. Unlike a passive system that relies on warm air to do the work, an active system uses a fan to help draw the radon out. There are a few different types of active radon mitigation systems. While they all work similarly, the placement of the fan and pipe installation will differ.

Active systems where the ventilation pipe is in the home's interior, the fan is located in the attic. Like with the passive system installed with a barrier, this option has the pipe running from the basement, sump pump room, or garage to the attic and then through the roof. In some cases, these mitigation systems are used in concert with a barrier. They are installed through the slab at the time of construction.

If you have a crawl space, consider adding a sub-membrane depressurization system to your home. This method lowers the pressure in your crawlspace through the use of a radon fan and PVC pipe. 

Finally, you can choose to have your active mitigation system installed outside your home. This method is much like adding a passive mitigation system to an older home. The difference is the fan, which the passive system does not include. Workers place the radon fan at ground level instead of in the attic.

How Effective is a Radon Barrier?

The overall effectiveness of a radon barrier or mitigation system depends on several factors, including how easily gas can move under the material and the climate where you live.

For example, according to EPA findings, an active mitigation system can be 50 to 99 percent effective. In comparison, a passive sub-slab system is only 30 to 70 percent effective. They also found that passive systems work best in colder climates.

Is There Such a Thing As a Safe Radon Level?

There is no official "safe level" for radon in a home. On average, the indoor air of homes has a radon concentration of 1.3 picocuries per liter (pCi/L). Outdoor air levels have an average concentration of 0.4 pCi/L.

Testing your home is the only way to determine if you need to take action. Ideally, you should have a professional come out and do testing to check levels if you are concerned. If your home has levels above 2 pCi/L, take action to remove the radon. Levels above 4 pCi/L are considered actionable, and at that point, you may want to consider installing a radon barrier to lower the levels.


Knowing the radon levels in your home is the first step to take before installing a radon barrier. If your levels aren’t actionable, it is time to install a barrier or system to help pull the gas out of your home and into the atmosphere. Radon barriers and mitigations methods effectively reduce the levels within your living space, keeping your family safe from hazardous levels of radioactive gas.