Where Radon Really Comes From—and Why It Ends Up in Your Home

Radon is a colorless, odorless, radioactive gas that is naturally present in soil, rock, and groundwater, which poses serious health risks to families across Tennessee. Understanding where radon comes from can provide valuable context and help you make informed decisions about protecting your home. Let’s explore the origins of radon and why it commonly enters Tennessee homes.

Radon’s Origins and Movement Through Soil

What does radon come from? The source is uranium found deep within the Earth’s crust. Uranium has been breaking down for billions of years, and as part of this natural process, it turns into radium, which then releases radon gas into the surrounding soil and rock.

When radon gas is created, it escapes from solid rock and soil particles and moves into the tiny air spaces between them. How much radon is released and how easily it travels depend on the type of soil and rock, their porosity, and the amount of moisture they contain. Loose or fractured soil and rock allow radon to move more freely.

Once radon gas forms underground, it can collect in the soil beneath homes. From there, it can enter a house through cracks in the foundation, gaps around pipes, or other small openings, where it may build up to unsafe levels indoors.

Environmental Factors That Influence Home Radon Levels

Although radon is naturally produced within soil layers, its entry into indoor structures is largely governed by two main factors: soil composition and pressure differences between the home and the surrounding ground.

Soil Composition and Permeability

How easily a type of soil allows radon gas to enter the atmosphere depends on its composition and permeability. Soils with larger, well-connected pore spaces (higher permeability), such as sandy or gravelly soils, allow radon to travel more freely from its point of generation toward the surface and a home’s foundation. Dense, fine-grained soils with low permeability, like clay, restrict radon movement. 

Weather and Pressure Differences

Pressure differences are a key cause of radon gas being pulled from the soil and seeping into homes and businesses. For example, more radon can be released into the air as pressure drops after a storm. The air inside buildings tends to have lower pressure than outdoor air, creating a vacuum-like effect that draws radon-laden soil gases upward and into the house. 

This phenomenon can be amplified by the stack effect, which occurs when warm indoor air rises and escapes through the upper levels of a building. As a result, negative pressure develops at the lower levels, pulling radon and other soil gases into the structure through foundation openings. The stack effect is why winter can bring higher radon levels.

Why Tennessee Has Naturally Higher Radon Levels

While several areas of the United States are known for high radon levels, radon levels in Tennessee can be higher. Many homes in Tennessee have an estimated average radon level of 4 picocuries per liter (pCi/L) or higher, which is the level the EPA recommends individuals take action. 

The primary reason for these elevated radon levels is the state’s unique geological makeup. Much of Middle Tennessee sits on limestone and other rock formations that naturally contain higher levels of uranium. In addition, parts of the state feature karst landscapes, which can create more pathways for radon to move from deep underground toward the surface and into structures.

Reasons Why Radon Enters a Home

So, where does radon in homes come from? Radon gas primarily enters a home through points of contact where the structure meets the ground. Here are four specific reasons why a home may have higher radon levels than others. 

High Presence of Radon in Soil

Some regions of the country, such as middle Tennessee, naturally have higher radon levels in the soil due to the types of rock and minerals underground. When higher amounts of radon are produced beneath a home, more of the gas is available to move upward and enter the building. This is why homes in the same neighborhood—or even next door to each other—can have very different radon levels.

Unsealed Gaps and Foundation Cracks

Small cracks and gaps in a home’s foundation are normal, but they provide easy entry points for radon gas. Radon only needs tiny openings to seep inside, especially around joints, utility penetrations, and sump pits. Even well-built homes can develop these gaps over time as materials settle and shift.

Older Home Age

Older homes often have more wear and tear in their foundations, which can lead to additional cracks or deteriorated seals. Old building standards also didn’t account for radon prevention, so many older homes lack protective features found in newer construction. As a result, radon can find more pathways into the home.

Seasonal Changes and Temperature Drops

Colder weather can cause homes to pull in more radon due to pressure differences between indoor and outdoor air. This causes the warm air to rise and escape, creating a vacuum effect that draws radon up from the soil.

How to Manage Your Home’s Radon Levels

High radon levels are a concern for any homeowner. Here is what to do if you suspect you have a radon problem.

Conduct a Radon Test

The only way to know whether you need to take action against radon is to test for it. Radon is invisible and odorless, so its presence can’t be detected without specialized equipment. Testing provides clear, measurable results that help homeowners understand their risk and determine whether mitigation is necessary.

Install a Radon Mitigation System

If you discover your home’s radon levels are at or above 4.0 pCi/L, you should reach out to a professional to install a radon mitigation system. Local experts like The Radon Guys can determine where radon is found in homes like yours and install the ideal system based on your house’s layout and radon risk. 

Our team is highly skilled and knowledgeable about the risks of radon in Middle Tennessee, and we work hard to design effective, customized mitigation solutions tailored to local homes. After a mitigation system is installed, a smart monitor can help you keep an eye on your levels and alert you to any changes that may need attention.

Get to the Bottom of a Radon Problem

If you’re concerned about how radon may be entering your home, The Radon Guys can help. Our mitigation systems are designed to stop radon at the source, rerouting it safely outside and reducing your exposure. Contact us today to learn how a custom mitigation solution can keep your home protected year-round.