Radon Mitigtion: What Homeowners Need to Know
This guide summarizes EPA, CDC, and Colorado state guidance on radon mitigation current as of 2026; engage a certified radon mitigation contractor for any system design or installation decisions. The search term “radon mitigtion” is a common typo for “radon mitigation,” the EPA-preferred technical term for the process of reducing indoor radon exposure. EPA and the radon industry deliberately use “mitigation” rather than “remediation” because radon does not behave like a contamination that can be cleaned up once. The soil-gas source continuously regenerates, so the mitigation system runs continuously to keep pace. This guide covers the mitigation-versus-remediation terminology distinction and walks through the typical sub-slab depressurization system that Front Range homeowners actually install.
Why EPA uses “mitigation” instead of “remediation”
The terminology distinction matters enough that EPA, AARST, and NRPP all standardized on “mitigation” decades ago. Remediation typically refers to the cleanup of an existing contamination — removing soil from a contaminated site, abating asbestos from a building, removing lead-based paint. Once remediation is complete, the hazard is gone (or at least bounded), and ongoing system operation is not needed.
Radon does not fit this model. The radioactive decay of uranium and radium in soil continuously produces new radon gas. Mitigation systems prevent the gas from entering the home, but the system must continue operating because the source continues regenerating. Calling it “remediation” implies a one-time fix; “mitigation” correctly implies an ongoing engineering control.
Other indoor air hazards follow the remediation model more closely. Mold remediation typically resolves once the moisture source is corrected and the mold itself is removed. Asbestos abatement resolves once the asbestos-containing material is removed. Radon is different precisely because the source is geological and continuous rather than confined to a specific material that can be removed from the home.
The “radon remediation” usage persists in colloquial language and in marketing materials from some contractors. The terminology is not strictly wrong in everyday conversation, but the technical-accurate term for the EPA-recommended process is mitigation.
What radon mitigation reduces and by how much
A properly designed mitigation system typically reduces indoor radon by 70-99% from pre-mitigation levels. The reduction depends on system design (single versus multiple suction points), home conditions (foundation type, sub-slab fill permeability, presence of radon-resistant new-construction features), and installation quality.
Front Range homes commonly start with pre-mitigation indoor radon at 4-15 pCi/L and reach post-mitigation levels at 0.5-2.0 pCi/L after a properly designed sub-slab depressurization (SSD) system is installed and verified. Homes with very high pre-mitigation levels (above 20 pCi/L) sometimes require multi-point systems or supplemental measures to reach acceptable levels, and post-mitigation levels in these homes commonly land in the 1-3 pCi/L range.
EPA’s action level of 4.0 pCi/L is the threshold at which mitigation is recommended; properly designed systems should reduce levels well below the action level to provide margin against system performance variation over time.
Sub-slab depressurization as the standard approach
The standard radon mitigation approach for slab-on-grade and basement homes is sub-slab depressurization (SSD). The system uses a continuous-duty fan to extract air from beneath the foundation slab and exhaust it above the roofline. Negative pressure in the sub-slab area reverses the pressure differential that was previously driving soil gas into the home.
SSD installation involves drilling a penetration through the foundation slab, clearing a small suction pit beneath the slab, sealing the penetration, running perforated PVC piping from the suction point to the mitigation fan, mounting the fan in the attic or on an exterior wall, terminating the exhaust above the roofline, and installing a manometer pressure gauge for ongoing operation verification.
Installation time is typically 4-6 hours on site. Cost in the Front Range market in 2026 runs $1,200-2,500 for a single-suction-point system on a typical single-family detached home. Multi-suction-point systems and combined SSD-plus-crawlspace mitigation systems run higher; see our residential radon mitigation guide for the full Front Range pricing breakdown.
Alternative mitigation approaches for non-slab foundations
Crawlspace foundations require a different approach. Sub-membrane depressurization (SMD) installs a sealed plastic membrane over the crawlspace floor, with the depressurization fan pulling air from beneath the membrane. The membrane acts as the sealing layer that the slab provides on SSD installations. SMD pricing runs $2,000-3,500 for a typical Front Range single-story crawlspace home.
Mixed-foundation homes (partial slab plus partial crawlspace) typically need both SSD for the slab portion and SMD for the crawlspace portion. Combined system pricing runs $3,000-5,000 depending on the relative size of each foundation type and the routing complexity.
Old stone or rubble foundation walls in pre-1900 homes are difficult to mitigate effectively because the porous walls leak air around the foundation perimeter, reducing the effective sub-slab suction. Mitigation approaches for these older foundations sometimes combine SSD with foundation wall sealing and supplemental sub-floor extraction. Pricing for these complex retrofits often exceeds $4,000-7,000.
What “mitigation” does not include
Radon mitigation systems address the soil-gas pathway. They do not address radon in well water — that requires a separate granular activated carbon (GAC) treatment system installed at the home water service entry. Homes with both elevated indoor air radon and elevated well-water radon need both mitigation approaches; addressing one without the other can leave residual exposure above the action level.
Mitigation systems also do not address general indoor air quality concerns beyond radon. Mold, volatile organic compounds, particulates, and other indoor air pollutants require separate mitigation approaches. Mitigation contractors sometimes recommend supplemental ventilation or filtration as complementary measures, but the radon mitigation system itself is focused on the radon pathway.
The mitigation system does not fix the soil-gas source. Underground uranium and radium continue to decay and produce radon regardless of what happens at the home. The system intercepts the soil gas before it enters the home; it does not affect the underground source.
Verification testing and ongoing operation
Post-installation verification testing happens 30-60 days after installation under the EPA closed-house protocol. The test uses a continuous radon monitor for 48 hours and produces documented results that should be at or below the EPA action level of 4.0 pCi/L (and typically well below — 0.5-2.0 pCi/L in well-designed systems).
The verification test is best performed by a third-party tester rather than the installation contractor. Third-party verification avoids the conflict-of-interest concern and produces more defensible documentation for property records.
Ongoing operation requires modest attention. The manometer pressure gauge should be checked monthly; a visible water-column pressure difference indicates the fan is operating. Zero pressure difference indicates fan failure or system leakage that should be addressed promptly. Periodic retesting every 2 years verifies the system is still effective.
For deeper context on the verification testing piece, see our radon testing inspection guide covering both pre-mitigation and post-mitigation testing.
Choosing a mitigation contractor
Certified mitigation contractors hold NRPP, AARST, or CDPHE credentials. All three certifications require initial training, examination, and continuing education. Front Range homeowners can verify credentials through the NRPP and CDPHE public databases before engaging a contractor.
Beyond certification, property owners should request 3-5 references from recent installations, confirm appropriate insurance coverage (general liability, workers compensation, errors and omissions), and verify the proposed system design is appropriate for the home’s specific foundation conditions. A contractor who proposes a single-suction-point SSD without diagnostic testing on a complex foundation is cutting corners.
Bid comparison should be apples-to-apples. Request itemized quotes that specify system components, installation labor, post-installation verification test cost, warranty terms, and any contingencies. Bids with lump-sum pricing and no itemization are harder to compare and sometimes hide padding in undisclosed line items.
System operational cost and energy use
Mitigation systems run continuously, which raises operational cost questions. The mitigation fan typically draws 30-90 watts under continuous operation, depending on the model. RadonAway RP145 draws about 70 watts; Festa AMG150 draws about 50 watts at the lower-noise operating point. Eagle Tech EZ200 falls in the same range.
At Front Range Colorado electricity rates, continuous operation of a typical mitigation fan costs $40-100 per year. The operational cost is generally accepted as part of owning a mitigated home; it is small compared to other home utility expenses and modest relative to the lung-cancer-risk reduction the system provides.
Heat loss through the mitigation exhaust pathway is a secondary cost concern. The system exhausts air to outdoor — air that has been conditioned by the home’s HVAC system. The conditioning energy loss is typically small (the exhaust airflow is modest) but contributes to whole-home energy use in cold-winter climates like the Front Range.
New construction radon-resistant features
Homes built after about 2010 in radon-prone areas often include radon-resistant new-construction (RRNC) features designed by the builder. RRNC includes a gas-permeable layer (typically 4 inches of clean gravel) under the slab, a sealed slab with all penetrations gasketed, and a passive vent stack running from the sub-slab area to above the roofline.
The RRNC features set up the home for easy mitigation activation if testing later shows elevated radon. Adding a fan to the existing vent stack typically costs $400-800 — substantially less than full retrofit SSD installation. Front Range homeowners in newer construction should ask the builder whether RRNC features were installed; the answer affects the cost of any future mitigation if it becomes needed.
Some Front Range counties have moved toward requiring RRNC in all new residential construction. Property owners building new construction in these jurisdictions should verify the RRNC scope and installation quality during the construction inspection.
Mitigation in real-estate transactions
Many Front Range real-estate transactions surface elevated radon during the inspection period. Standard contract objection language allows buyers to request mitigation as a transaction condition, and sellers commonly agree to install mitigation before closing. The seller-paid mitigation arrangement is the most common pattern in the Denver metro market.
Alternatively, sellers can credit the buyer at closing for the estimated mitigation cost, with the buyer arranging installation post-closing. This arrangement works when the buyer wants to control the contractor selection or when scheduling pressure prevents pre-closing installation. The credit amount should reflect realistic local mitigation pricing rather than a lowball estimate.
Sellers who proactively test and mitigate before listing the property typically command modest pricing premiums and avoid the inspection-objection negotiation entirely. The mitigation system becomes a positive disclosure rather than a defensive response to buyer objections.
What to expect from a properly designed mitigation system over decades
A properly installed mitigation system should provide effective radon reduction for the life of the home with periodic minor maintenance. The fan is the wearing component; expect to replace it once or twice across a 30-50 year ownership window. PVC piping, slab seals, and the manometer typically last the life of the home without significant attention.
Periodic retesting every 2 years remains the EPA recommendation. The retest catches gradual performance changes and confirms the system continues to maintain indoor radon below the action level. Front Range homeowners who skipped post-installation testing or who installed mitigation many years ago without follow-up testing should retest now to verify continued effectiveness.
Documentation of the mitigation system and testing history adds modest value at resale. Buyers shopping in Front Range markets often look favorably on homes with documented mitigation and recent verification testing, since those features reduce the buyer’s uncertainty about radon during the inspection-objection period.
References
- EPA Consumer Guide to Radon Reduction — US Environmental Protection Agency
- CDC radon mitigation and exposure guidance — Centers for Disease Control and Prevention
- Colorado CDPHE radon mitigation program and certified contractors — Colorado Department of Public Health and Environment
Front Range homeowners weighing mitigation options can reach out through our contact page for a referral to a certified mitigation contractor in the Denver metro area.