For quickly Reducing radon levels, immediately increase natural ventilation by opening windows on the lowest floors and running fans. However, for long-term safety, install an Active Soil Depressurization (ASD) system. This permanent, professional fix draws gas from beneath your foundation and vents it safely outdoors, reliably cutting levels by 80 to 90%.
Radon is a naturally occurring radioactive gas. It forms when uranium breaks down in soil and rock, then seeps into homes through foundation cracks, sump pits, and gaps around pipes. The U.S. Surgeon General and EPA identify radon as the second-leading cause of lung cancer in the United States, after smoking. Reducing radon levels isn’t optional once a test confirms elevated readings it’s a health necessity.
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Why Reducing Radon Levels Matters
Radon exposure is cumulative. The longer a home sits at an elevated level, the higher the lifetime lung cancer risk, and that risk multiplies for smokers exposed to radon at the same time.
Homes with unfinished basements, homes built over cracked or porous bedrock, and homes with gaps around sump pits or utility penetrations tend to test higher, though soil conditions vary enough that two houses on the same block can post very different results. For a deeper look at how radon forms and moves through a foundation, see what makes radon dangerous.
How Do You Know If Your Radon Levels Are High?
The only way to know your home’s radon concentration is to test it. Short-term test kits measure levels over 2–7 days; long-term kits measure over 90 days or more for a more accurate annual average.
Continuous radon monitors, used by professionals, provide hour-by-hour data and are less prone to tampering or weather-related spikes. Weather conditions especially barometric pressure changes and heavy rain can temporarily elevate readings, so understanding how testing conditions affect results matters before drawing conclusions from a single test.
If your result comes back at or above 4.0 pCi/L, retest to confirm, then schedule mitigation.
How to Reduce Radon: Methods That Actually Work
The right method depends on your foundation type and how the test came back. The table below summarizes what EPA’s Consumer’s Guide to Radon Reduction documents for typical reduction ranges by method.
| Method | Typical Reduction* | Best For |
| Active sub-slab depressurization (ASD/SSD) | 50–99% | Basements and slab-on-grade homes; the standard fix |
| Passive sub-slab suction | 30–70% | New construction with a passive pipe already roughed in |
| Sub-membrane (crawl space) depressurization | 50–99% | Homes with a crawl space and a sealed vapor barrier |
| Sealing cracks and openings alone | Not reliable on its own | Supplementing an active system, not replacing one |
| Increased ventilation (opening windows, HRVs) | Variable, temporary | Short-term dilution below the action level only |
Ranges per EPA’s Consumer’s Guide to Radon Reduction. Actual results depend on soil permeability, foundation type, and system design.
Sub-Slab Depressurization (Most Effective)
A licensed technician drills through the foundation slab, inserts a PVC pipe into the crushed rock or soil below, and connects it to a radon fan that runs continuously.
The fan creates negative pressure under the home, so radon gets pulled out and vented above the roofline instead of drawing indoors. This is the method EPA and ANSI/AARST mitigation standards treat as the default for basement and slab-on-grade homes.
Sealing Foundation Cracks and Openings
Sealing alone rarely brings radon below the action level, but it makes an active system more efficient by closing off competing entry points. Technicians typically seal:
- Foundation cracks and expansion joints
- Sump pit covers
- Gaps around utility penetrations
- Openings in crawl space vapor barriers
Radon finds new pathways once the obvious ones are blocked, which is why EPA doesn’t consider sealing adequate mitigation by itself.
Crawl Space Encapsulation
Homes with crawl spaces get a sealed vapor barrier paired with a depressurization pipe run underneath it, sometimes called sub-membrane depressurization. It treats radon the same way sub-slab suction does, by venting gas before it reaches the living space, and it usually loses less heat in winter than relying on natural crawl space ventilation.
Ventilation and Pressure Adjustments
Heat recovery ventilators and increased mechanical ventilation dilute indoor radon somewhat, but this is a supplementary step, not a standalone fix, and it raises energy costs. It’s rarely the right primary strategy once a home tests above the action level.
Treating Radon in Well Water
Homes on private well water can have radon dissolved in the water itself, which releases into the air during showers and laundry. Aeration systems and granular activated carbon filters strip radon out before it reaches household taps. If your home is on well water, radon water testing should be part of the overall assessment, separate from an air test.
Can You Reduce Radon Without Hiring a Contractor?
Store-bought sealants and box fans can’t replicate the pressure diagnostics, pipe sizing, and fan selection a proper system needs. Installed wrong, a system can pull radon into the home instead of venting it out, or simply fail to move the needle.
NRPP- and NRSB-certified technicians follow ANSI/AARST design and post-mitigation testing standards, which matters more in Wisconsin than in states with their own contractor licensing, since Wisconsin has no separate state radon license and national certification is the credential to check.
For a closer look at where DIY falls short, see does DIY radon mitigation work, and for what to look for in a contractor, see how to hire certified radon mitigation in Milwaukee.
What Does It Cost to Reduce Radon?
Cost depends on foundation type, house size, and how many suction points the system needs, so a single number here would be more misleading than helpful. For a full breakdown of what drives the price up or down, see the cost of radon mitigation and what affects pricing.
Ongoing costs are modest, the fan draws a small, steady amount of electricity, but fans do wear out over time. For guidance on fan basics and when replacement makes sense, see what a radon fan is and how it works and when should you replace a radon fan.
How Long Does It Take to Reduce Radon Levels?
A properly installed sub-slab depressurization system starts reducing radon within 24 hours of activation. Full installation, including drilling, piping, and fan setup, typically takes one day for a single-family home.
Post-mitigation testing, done anywhere from 24 hours to 30 days after activation, confirms the system brought levels below 4.0 pCi/L. Retesting every two years afterward confirms the system is still performing, since fans can lose efficiency or fail.
Reducing Radon Levels in Milwaukee Homes
Milwaukee’s mix of older housing stock and newer builds means foundation types vary block to block, which is part of why homes here can show a high radon level even next door to a home that tests low.
Because EPA’s zone map isn’t precise enough to substitute for an actual test, the only reliable step for any Milwaukee homeowner is to test the specific house, not to assume based on the neighborhood or the county’s general classification.
Milwaukee Radon Home installs ANSI/AARST-compliant radon mitigation systems throughout the Milwaukee, WI area, with NRPP-certified technicians handling design, installation, and post-mitigation testing.
Call (414) 455-7279 to schedule a radon test or mitigation consultation today.
Frequently Asked Questions
What is considered a high radon level?
The EPA action level is 4.0 pCi/L. Levels between 2 and 4 pCi/L still carry risk, and the EPA recommends considering mitigation in that range as well.
Can opening windows reduce radon levels?
Temporarily, yes, but it’s not a permanent or reliable solution. Radon returns to previous levels once windows close, and it isn’t a substitute for a mitigation system.
Does radon mitigation completely eliminate radon?
No system removes radon entirely, but a properly installed sub-slab depressurization system typically reduces levels by 80–99%, bringing most homes well below the action level.
How often should I retest after mitigation?
Retest immediately after installation, then every two years, and after any major renovation to the foundation or HVAC system.
Is radon mitigation a one-time cost?
The system installation is a one-time cost, but fans have a service life of 5–10 years and will need periodic replacement or inspection.
Conclusion
Knowing how to reduce radon starts with an accurate test, not a quick fix. Opening windows buys time, sealing helps at the margins, but a professionally installed depressurization system is the only method EPA data backs as a reliable, lasting solution.
If your home has tested at or above 4.0 pCi/L, or you haven’t tested at all, Milwaukee Radon Home’s mitigation team can walk you through testing, system design, and post-installation verification.
