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A radon mitigation system pulls radon gas from beneath your home’s foundation and vents it outside before it can build up indoors. Most systems use a pipe and a continuously running fan — installation typically takes four to six hours.
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Why Does Denver Have a Radon Problem Worth Solving?
Denver sits in EPA Zone 1 — the highest-risk radon category — and Colorado’s geology explains why. The granite and uranium-rich bedrock underlying much of the Denver metro naturally produces radon gas as uranium decays in the soil. That gas seeps upward through soil and into homes through cracks in foundation slabs, gaps around pipes, and exposed crawl space floors.
Colorado’s statewide indoor radon average runs around 6.3 pCi/L — well above the EPA action level of 4.0 pCi/L. In the Denver metro, we typically see roughly half of tested homes come back elevated. The stack effect makes things worse in winter: as warm indoor air rises and escapes through the upper floors, it draws soil gas — including radon — upward through the foundation. Summer months can mask the true picture, especially when windows are open, which is why understanding when to test and what your numbers actually mean matters as much as the test itself.
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What Exactly Does a Mitigation System Do?
A mitigation system doesn’t filter radon — it redirects it. The system creates a pressure difference that pulls soil gas away from beneath the slab before it can enter the living space.
The most common method is sub-slab depressurization (SSD). A contractor cores a hole through the foundation slab, inserts a PVC pipe, and connects it to a fan mounted either in the attic, garage, or exterior wall. The fan runs continuously, drawing radon-laden air out from under the slab and venting it above the roofline where it disperses safely.
In homes with crawl spaces, the approach shifts slightly — a vapor barrier covers the exposed soil, and the same suction principle applies through a pipe that runs through or alongside the barrier. Sump pits can also serve as suction points when they’re present and properly sealed.
The system doesn’t require any special maintenance schedule beyond periodic fan checks. Most fans run quietly and are designed to operate continuously for 10 to 20 years before needing replacement.
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What Happens During a Typical Installation?
Most residential installs in the Denver area wrap up in four to six hours, depending on the home’s foundation type and size.
The process generally goes like this: a technician first does a diagnostic walkthrough to identify the foundation type — poured slab, block wall, crawl space, or a combination — and locate the best suction point. A core drill bores through the slab, and the technician checks for proper suction by testing the sub-slab communication, essentially confirming that the fan will pull from the right area.
The pipe gets routed through the home — often through a closet or interior wall — and exits through the roof, or runs up an exterior wall depending on the home’s layout. The fan is installed and wired to a dedicated electrical circuit, and a U-tube manometer (a simple visual gauge) is mounted on the pipe so homeowners can confirm the system is working at a glance.
A post-installation radon test follows, usually conducted 24 to 48 hours after the system is running. Most Denver contractors schedule this as part of the job, and results come back within a few days.
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How Much Does a Mitigation System Cost in Denver?
Costs for a standard single-family home in the Denver metro typically fall between $950 and $2,500, with most installs landing around $1,200 to $1,500.
The table below reflects typical ranges for common scenarios:
What Should You Expect to Pay for Radon Mitigation in Denver?
| Scenario | Estimated Cost | Notes |
|---|---|---|
| Single suction point, poured slab | $950 – $1,400 | Most common setup in Denver |
| Multiple suction points needed | $1,400 – $2,000 | Larger homes, complex foundations |
| Crawl space with vapor barrier | $1,200 – $2,000 | Barrier included if not present |
| Sump pit conversion | $800 – $1,200 | Existing sump used as suction point |
| Fan replacement (existing system) | $200 – $450 | Fan only, no new pipe work |
| Electrical hookup (if not included) | $200 – $400 | Separate electrician sometimes needed |
| Annual inspection/maintenance | $0 – $150 | Fan check, manometer reading |
Low-income Denver households may qualify for Colorado’s Low Income Radon Mitigation Assistance Program, which can offset up to $1,500 of installation costs for eligible owner-occupied homes.
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How Do You Know the System Is Working?
A properly installed system should bring radon levels below 4.0 pCi/L — often well below 2.0 pCi/L — within the first few days of operation.
The U-tube manometer mounted on the pipe gives a quick visual read: if the fluid levels are uneven, the fan is pulling suction as designed. If they’re level, the fan may have failed or the pipe is blocked.
Beyond the visual check, retesting the home is the only way to confirm performance. A short-term charcoal canister test ($15–$40 for a DIY kit, or $150–$250 professionally) placed in the lowest occupied level gives a reliable reading after 48 to 96 hours. For ongoing peace of mind, a continuous radon monitor — devices like those made by Airthings run $150 to $300 — lets you watch levels in real time from a phone app.
Colorado’s action level guidance recommends retesting every two years even with a working system, and after any major renovation that changes the foundation or ventilation.
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When Should You Call a Professional Instead of Going DIY?
If your test results are at or above 4.0 pCi/L, professional installation is the right call — not a judgment call. Colorado requires radon mitigation contractors to be licensed through the Colorado Department of Regulatory Agencies (DORA), and for good reason.
DIY mitigation kits exist and cost $500 to $1,000, but improper suction placement, undersized fans, or inadequate sealing can fail to reduce levels — or in some cases push radon into living spaces rather than out of them. Denver’s varied foundation types (older homes near Capitol Hill often have rubble-stone foundations, newer construction in Stapleton or Highlands Ranch may have different slab configurations) require a diagnostic read before any pipe goes in.
Call a licensed professional if:
- Any test result comes back at 4.0 pCi/L or higher
- You’re buying or selling a home — Colorado requires radon disclosure in real estate transactions
- Your existing mitigation system’s manometer shows no suction
- You’re finishing a basement and changing the foundation’s exposure
- You’ve had the same system for more than 15 years without inspection
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What Should Denver Homeowners Do Next?
If you haven’t tested yet, start there. Short-term charcoal canister kits are available at hardware stores and online for $15–$40. Place the test in the lowest regularly used room — basement, main floor if no basement — away from windows and exterior doors. Follow closed-house conditions for at least 12 hours before and during the test.
If results come back between 2.0 and 4.0 pCi/L, a follow-up long-term test or continuous monitor will give you a more complete picture before deciding on mitigation. Above 4.0 pCi/L, schedule a professional assessment. Most licensed Denver-area contractors can schedule an initial consultation within a few business days, with installation typically completed in a single visit.
RadonSweep connects Denver homeowners with licensed Colorado radon professionals who know the local geology, building stock, and permit requirements — so the system gets designed for your specific home, not a generic floor plan.
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FAQ
Q: How long does a radon mitigation system last?
Most systems run reliably for 10 to 20 years. The fan is the only component that typically needs replacement, usually around the 10-year mark.
Q: Will the system be loud or disruptive inside my home?
No. Properly installed fans are quiet — comparable to a bathroom exhaust fan. Most homeowners forget it’s running.
Q: Does a mitigation system need to run constantly?
Yes. The fan should run 24/7. Turning it off allows sub-slab pressure to equalize and radon levels to rise again within hours.
Q: Can a mitigation system be installed in a home without a basement?
Yes. Slab-on-grade homes and crawl space foundations both have effective mitigation options, including sub-membrane depressurization for crawl spaces.
Q: Does opening windows in summer lower radon enough to skip mitigation?
No. Open windows temporarily dilute radon but levels return quickly when they close. Summer readings may also understate year-round exposure.
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Sources
- U.S. Environmental Protection Agency: “Consumer’s Guide to Radon Reduction” and radon action level guidance
- Colorado Department of Public Health and Environment: Radon program information, mitigation cost estimates, and Low Income Radon Mitigation Assistance Program details
- Colorado Department of Regulatory Agencies (DORA): Radon mitigation contractor licensing requirements
- Colorado Geological Survey: Radon occurrence and geology of Colorado
- Colorado Environmental Public Health Tracking: Statewide radon statistics and real estate disclosure requirements