Radon Mitigation System: What Homeowners Should Know
When a radon test comes back high, the next question is almost always the same: what now? The answer, in most homes, is a radon mitigation system, a permanently installed setup that pulls radon gas from beneath the foundation and vents it safely above the roofline. Colorado has some of the highest radon potential in the country, so Front Range homeowners deal with this more than most. This guide summarizes EPA and state guidance current as of 2026 for educational purposes; it is not a medical diagnosis, and a certified radon professional should design and verify any system installed in your home.
What Is a Radon Mitigation System?
A radon mitigation system is engineered to reduce the concentration of radon gas inside a building. The EPA recommends action when a long-term indoor level reaches or exceeds 4 picocuries per liter (4 pCi/L), and a properly designed system routinely brings levels well below that threshold, often under 2 pCi/L. The most common design is called active soil depressurization. It uses a continuously running fan and a sealed pipe to create suction under the slab or in the crawl space, capturing radon before it can seep into living areas and exhausting it outdoors.
The principle is simple. Radon is produced by the natural decay of uranium in soil and rock. It moves toward lower-pressure indoor air through cracks, sump pits, and gaps around plumbing. A mitigation system reverses that pressure relationship so the gas takes the path of least resistance up the vent pipe instead of into the house.
How Does an Active Soil Depressurization System Work?
The typical sub-slab depressurization system has a few core parts. A suction point is created by cutting through the concrete slab and removing some of the gravel or soil beneath to form a small cavity. A PVC pipe is sealed into that point and routed, either through the interior or up an exterior wall, to a discharge above the roof eave. An inline fan, mounted in the attic or outside, runs continuously to maintain suction.
A visible manometer, a simple U-shaped gauge filled with colored liquid, is installed on the pipe. When the system is working, the liquid columns sit at different heights, confirming the fan is pulling a vacuum. If both columns level out, the fan has likely failed. The system label and the manometer are how a homeowner confirms ongoing operation at a glance.
Variations for Different Foundations
Slab-on-grade and basement homes usually get sub-slab depressurization. Homes with crawl spaces often use sub-membrane depressurization, where a heavy plastic membrane is sealed over the crawl-space floor and the fan draws radon from beneath it. Homes with multiple foundation types may need more than one suction point. A certified installer matches the design to the structure rather than applying a single template.
How Much Does a Radon Mitigation System Cost?
National figures from the EPA and radon industry sources place most residential radon mitigation systems in roughly the $800 to $2,500 range, with typical Front Range installations often landing near the middle of that band. Cost depends on foundation type, the number of suction points, pipe routing, and whether the discharge runs through the interior or up an exterior wall. Homes that need multiple suction points or complex routing sit at the higher end.
Operating cost is modest but real. The fan runs continuously and uses electricity, and it adds a small amount of conditioned-air loss through the vented soil gas. Most homeowners see a minor bump in their utility bill rather than a significant expense. Fans eventually wear out, and planning for that is part of owning a system; our breakdown of radon fan replacement cost covers what to budget when that day comes.
Do You Always Need a System After a High Test?
Not necessarily on the first reading. A single short-term test can be skewed by closed-house conditions, weather, or the testing season. The EPA recommends confirming an elevated short-term result with either a second short-term test or a long-term test before committing to mitigation. Once a confirmed level at or above 4 pCi/L is established, an active system is the reliable path to a durable reduction.
Some minor improvements, such as sealing obvious foundation cracks, can help a little but rarely solve the problem alone. The EPA is clear that sealing by itself is not a reliable mitigation method. It is best treated as a supplement that makes the fan-driven system more efficient, not a substitute for it. To understand how the underlying numbers are produced, our guide to the radon testing process for Colorado homeowners explains short-term versus long-term measurement.
Choosing and Maintaining a Radon Mitigation System
Pick a contractor who holds national certification, such as credentials recognized by the National Radon Proficiency Program or the National Radon Safety Board. A qualified installer follows recognized standards, sizes the fan to the home, places the discharge correctly relative to windows and the roofline, and performs a post-installation test to confirm the level dropped below 4 pCi/L. That follow-up test is not optional; it is how you know the system actually worked.
Maintenance is light. Check the manometer periodically to confirm the pressure differential, keep the discharge area clear, and plan to replace the fan roughly every 5 to 10 years depending on the model. The EPA also recommends retesting the home every two years and after any major renovation, since structural changes can alter how soil gas enters. Pairing a system with steady attention to how radon fans perform over time keeps protection consistent.
Passive vs. Active Radon Systems
Not every radon system has a fan. Many newer homes are built with a passive system, a vent pipe routed from beneath the slab up through the roof that relies on natural air pressure and the stack effect to draw soil gas upward. Passive systems are cheaper to install during construction and run silently with no electricity, but they are also less reliable, often reducing radon only modestly.
When a passive system fails to bring levels below 4 pCi/L, the fix is usually to convert it to an active system by adding an inline fan. Because the pipe is already in place, that conversion is far cheaper than a full retrofit. Homeowners who buy a house with a passive system should still test, since the presence of a pipe does not guarantee the level is controlled. The EPA recommends that any radon-resistant new construction be tested after move-in to confirm the passive design is actually working.
Radon-Resistant New Construction
Builders increasingly use radon-resistant construction techniques, sometimes called RRNC, which install a gravel layer, a plastic sheet, a sealed vent pipe, and a junction box for a future fan during the build. These features make later mitigation simpler and cheaper. In high-radon regions like much of Colorado, some local codes encourage or require these measures, though a finished system with a running fan is still the most dependable way to keep levels down.
How Is a Radon Mitigation System Installed?
A typical installation takes a qualified contractor part of a day. The process begins with a diagnostic look at the foundation to choose the best suction point, often near the center of the slab or close to an existing sump pit. The installer cores a hole through the concrete, excavates a small pit beneath to create a suction cavity, and seals a PVC pipe into the opening with airtight caulk or polyurethane.
The pipe is then routed to the discharge point. An interior route runs up through closets, the garage, or chases and exits above the roof; an exterior route runs along an outside wall to a point above the eave. The inline fan is mounted in the attic or outside, never in living space, so any leak discharges soil gas outdoors. The installer adds a manometer, labels the system, seals visible foundation cracks and the sump lid to improve efficiency, and restores power to the fan.
The final and non-negotiable step is a post-installation test. The contractor measures radon after the system has run long enough to stabilize, confirming the level dropped below 4 pCi/L. That report is the homeowner’s proof the investment worked, and it belongs in the home’s permanent records, especially for a future sale.
Do Radon Systems Affect Energy Bills or Comfort?
A radon fan runs continuously, so it adds a small, steady draw to the electric bill, on the order of a low-wattage appliance. The system also pulls a modest amount of conditioned air loss through the soil-gas pathway, which can slightly affect heating and cooling efficiency. For most homes the combined impact is minor and far outweighed by the health benefit of controlled radon.
Comfort is rarely affected when the system is installed correctly. A properly mounted fan is quiet from inside the home, and the sealed pipe does not introduce drafts. Noise complaints almost always trace to a fan placed in living space, a failing bearing, or vibration transferring through mounting brackets, all of which a qualified installer avoids. Pairing the system with attention to basement humidity and ventilation keeps the home comfortable while the fan does its job, and our broader radon testing guidance explains how to verify the reduction held.
Common Problems and How They’re Fixed
Even a well-built system can develop issues over years of service. The most common is fan failure, signaled by a manometer whose two liquid columns have leveled out. A replacement fan, matched to the original sizing, restores the suction. Another issue is a cracked or disconnected pipe joint, which reduces vacuum and lets radon climb; resealing the joint solves it. Debris or a bird nest blocking the exterior discharge can also impede airflow and is cleared easily.
Less obviously, a home that has been renovated, finished, or had its HVAC changed can alter how soil gas moves, sometimes pushing a previously controlled level back up. This is why the EPA recommends retesting after major work. If a retest shows elevated radon despite a running fan, a contractor may add a second suction point, upgrade to a more powerful fan, or reseal newly opened pathways. The system is adaptable, and most performance problems trace to a specific, fixable cause rather than a fundamental flaw.
Reading Your Manometer
The manometer is the homeowner’s window into system health. Its U-shaped tube holds colored liquid, and when the fan pulls a vacuum the two columns sit at different heights. Memorize the normal difference shortly after installation so you have a baseline. If the columns ever level out, the fan has likely stopped and radon may be rising. A glance at this gauge takes seconds and is the single most useful maintenance habit a homeowner can build.
Will a System Affect Selling Your Home?
Far from a liability, a documented radon mitigation system is usually an asset when selling on the Front Range. Many Colorado buyers test for radon during their inspection contingency, and a home that already has a system with a passing post-installation test removes a common point of friction. The visible pipe and fan, paired with paperwork showing the level was brought below 4 pCi/L, reassure buyers that the issue was handled professionally.
Keep the original installation records, the post-installation test result, and any maintenance or fan-replacement history together in the home’s file. Hand these to the buyer at sale. A system without documentation can prompt a buyer to retest and renegotiate, while a fully documented one supports a smooth transaction. Treating the system’s paperwork as part of the home’s permanent records turns the mitigation investment into a selling point rather than a question mark.
Key Takeaways for Front Range Homeowners
A radon mitigation system is a proven, affordable way to bring a confirmed high level below the EPA action threshold of 4 pCi/L and keep it there. The active soil-depressurization design, a sealed pipe, a continuously running fan, and a discharge above the roofline, reliably suppresses radon when it is engineered to the home’s foundation and soil. Confirm an elevated test before committing, choose a certified installer, and insist on a post-installation test that documents the reduction.
Once installed, the system asks little: a glance at the manometer now and then, a fan replacement every several years, and the EPA-recommended retest every two years. Given Colorado’s high-radon geology, that modest ongoing effort buys durable protection against a serious long-term health risk, and it leaves the home with documented proof that the issue was handled, an asset whenever it comes time to sell.
References
- Consumer’s Guide to Radon Reduction — U.S. Environmental Protection Agency
- Health Risk of Radon — U.S. Environmental Protection Agency
- Radon in Colorado Homes — Colorado Department of Public Health and Environment
If a test has come back high and you want a certified installer to design the right system for your foundation, Front Range homeowners can reach a vetted local radon professional through our contact page.
Radon mitigation fans & parts
If a sub-slab depressurization system is the fix, the inline fan is the heart of it. Match the fan to your soil and pipe diameter — or have a certified installer size it.
| Product | Why | Buy |
|---|---|---|
 RadonAway RP145 Inline Fan | Common 4-in. SSD workhorse fan. | Amazon — $152.00 |
 Fantech Rn2 Radon Fan | Quiet operation; energy-efficient. | Amazon — $148.29 |
 Radon U-Tube Manometer | Confirms the system is pulling suction. | Amazon — $10.99 |