Radon Mediation: The Typo and the Actual Mitigation Guide
“Radon mediation” is almost always a typo for “radon mitigation.” Mediation is a legal process for resolving disputes between two parties. Mitigation is the engineering practice of reducing radon concentrations in a home that has tested above EPA’s action level of 4.0 pCi/L. The two words look similar; the practices are entirely unrelated. This guide covers the mitigation work that searchers are actually looking for — the system types, the regulatory framework, the Front Range Colorado cost ranges in 2026, and what post-installation verification looks like. Guidance summarizes EPA, CDPHE, and InterNACHI sources current as of 2026.
Radon mediation vs radon mitigation: the terminology fix
The word people typed when they searched “radon mediation” was almost certainly intended as “radon mitigation.” A few legitimate uses of “mediation” do exist in adjacent contexts — a homeowner-builder dispute over radon-resistant new construction (RRNC) features, a buyer-seller dispute over post-test mitigation responsibility — but these are legal processes between people, not engineering interventions in a home.
The substantive content this search is looking for is mitigation. The federal framework, the system designs, the costs, and the verification protocols all live in the mitigation literature. The rest of this guide walks through that material.
What radon mitigation actually is
Radon mitigation is the design and installation of an engineered system that reduces indoor radon concentration to acceptable levels. EPA’s action level — the concentration at which mitigation is recommended — is 4.0 pCi/L. EPA’s consideration threshold is 2.0 pCi/L, the level at which mitigation may still be appropriate for some households. Properly designed and installed mitigation systems typically reduce indoor radon by 50–99%, often bringing 8–15 pCi/L homes below 2.0 pCi/L after installation.
The federal framework recognizes several mitigation methods, with active sub-slab depressurization (ASD) as the gold standard for basement and slab-on-grade homes. Other methods — sub-membrane depressurization, drain-tile depressurization, block-wall depressurization, and heat-recovery ventilation — apply to specific foundation types or supplemental cases.
Active sub-slab depressurization (ASD): the gold standard
ASD installs a permanent pipe through the basement floor slab (or slab-on-grade floor) connected to a continuously running radon fan that exhausts soil gas to the outdoors above the roofline. The system creates negative pressure in the soil immediately below the slab, intercepting radon-bearing soil gas before it can enter the home through floor cracks, slab penetrations, or the slab-wall joint.
The standard ASD installation includes:
- A 4-inch or 6-inch PVC pipe penetrating the slab in a strategically chosen location (often near a sump pit or a known soil-gas accumulation point)
- A suction pit or excavated cavity below the slab to provide a pressure-field zone
- The pipe routed vertically through the home, through an unconditioned space (often a closet, utility room, or garage), and out through the roof
- A radon fan (typically 90–180 watts) installed in an unconditioned location — attic or exterior wall — to keep any fan-side leaks outside the conditioned envelope
- A U-tube manometer or pressure gauge near the fan that shows the system is operating
- An audible or visual failure alarm where required by local code
- Sealing of major entry pathways (slab-wall joint, slab cracks, sump cover) to maximize system effectiveness
ASD installation typically takes one workday. Most Front Range mitigation contractors complete the diagnostic assessment, system installation, and customer walkthrough in a single visit. Post-installation testing follows within 30 days.
Other mitigation methods and when they apply
Sub-membrane depressurization (SMD)
Used for crawl-space foundations. A polyethylene membrane is sealed over the crawl-space floor, and a fan creates negative pressure under the membrane. Effective for radon entering through crawl-space soil exposure.
Drain-tile depressurization
Where the home has a perimeter drain-tile system (footing drain) connected to a sump, the drain-tile loop can sometimes serve as the suction collection point instead of (or in addition to) a sub-slab suction pit.
Block-wall depressurization (BWD)
Used for homes with hollow-block foundation walls that act as a radon entry path. A fan draws negative pressure on the interior wall cavity, intercepting radon before it enters the conditioned space.
Heat-recovery ventilation (HRV) and energy-recovery ventilation (ERV)
Supplemental measures that increase whole-house air exchange, diluting indoor radon. HRV/ERV is rarely used as a standalone mitigation but can supplement a primary depressurization system when post-installation testing is borderline.
Radon-resistant new construction (RRNC)
For new construction in EPA Zone 1 areas (which includes most Front Range counties), building practice includes a passive radon-resistant rough-in: a vent pipe stub through the slab, routed through the home to a roof termination, and a junction box for a future fan. When post-construction testing finds elevated radon, the homeowner activates the rough-in by installing the fan — a substantially cheaper retrofit than installing a new system from scratch.
EPA RMS-LL: the standard of practice
EPA’s Radon Mitigation Standards for Low-Level (RMS-LL) framework — and its earlier RMS reference — sets the standard of practice for mitigation systems. Most state programs and most contractor certification programs reference EPA RMS-LL or the AARST/ANSI consensus standards (SGM-SF for soil-gas mitigation in single-family homes, and CC-1000 for radon-resistant new construction) as the design and installation baseline.
RMS-LL covers system component requirements, design pressure-field criteria, sealing requirements, fan specifications, exhaust termination, electrical wiring, labeling, and homeowner documentation. A contractor working to RMS-LL produces a system that meets EPA-recognized quality criteria.
CDPHE certification and Colorado-specific requirements
Colorado regulates radon mitigation contractors through CDPHE. Mitigation professionals working in Colorado must hold either a National Radon Proficiency Program (NRPP) or National Radon Safety Board (NRSB) credential. CDPHE does not run a separate state certification on top of the national programs but enforces compliance with NRPP/NRSB standards.
Verification steps for any Front Range mitigation contractor:
- Ask for the contractor’s NRPP or NRSB certification number
- Look up the certification on the relevant program’s online roster
- Confirm the certification covers mitigation (separate from measurement-only certifications)
- Verify the company is registered as a business and carries liability insurance
- Request references from local installations and check installed-system photos
Front Range cost ranges in 2026
Typical Front Range Colorado pricing for residential radon mitigation:
Standard ASD on a basement home — $1,100–1,800
Single suction point through the basement slab, fan in an attic or exterior location, roof termination. This covers the typical Denver, Boulder, and Colorado Springs metro home.
Slab-on-grade home — $1,200–2,000
Comparable to basement ASD but the slab penetration is from the conditioned interior, which adds finish-work considerations.
Crawl-space home — $1,500–2,500
Sub-membrane depressurization with full crawl-space encapsulation. Crawl-space access difficulty and total crawl footprint drive the variation.
Complex home — $2,000–4,000
Homes with multiple foundations (basement plus addition with crawl space), multiple separate suction points, or restricted roof-termination paths. Larger homes with very high pre-mitigation readings sometimes require dual fans or multiple suction points.
Post-installation verification testing
$125–200 for a professional CRM-based 48-hour test, or $15–30 for a homeowner-conducted charcoal canister test. Most contractors include one verification test in the installation price.
RRNC fan activation (when the rough-in already exists) typically runs $400–800 — fan, junction-box wiring, manometer, and verification.
The mitigation workflow from contract to verification
Step 1: Diagnostic assessment
The contractor performs a walkthrough — foundation type, slab condition, sump location, HVAC layout, existing penetrations. Some contractors run a quick pressure-field extension test (PFE) to map how far negative pressure under the slab will reach from a candidate suction point.
Step 2: System design
Suction point location, pipe routing, fan model, roof termination point. The design considers code requirements (especially for fan location relative to the home’s combustion appliances and roof-penetration setbacks from openings) and homeowner aesthetic concerns.
Step 3: Installation
Slab core drilling, suction pit excavation, pipe assembly, fan installation, electrical hookup, sealing of major entry pathways (slab-wall joint, sump cover, visible slab cracks). Typical one-day install.
Step 4: Walkthrough and documentation
Contractor demonstrates the manometer reading, explains the fan’s expected life (5–10 years for typical residential fans), provides the installation documentation, and starts the verification test.
Step 5: Verification testing
Post-installation test, typically 48 hours, started no sooner than 24 hours after fan startup. The test confirms the system is working and brings the documented indoor radon concentration below the EPA action level.
Step 6: Ongoing maintenance
Check the manometer monthly to confirm the system is still operating. Re-test the home every 2 years to confirm continued effectiveness. Replace the fan when it fails (typical 5–10 year life). EPA recommends keeping post-installation radon concentrations below 2.0 pCi/L where practical.
What can go wrong
Mitigation is generally reliable, but failures happen. The most common:
- Suction point misplaced relative to the soil-gas plume — the system runs but post-test radon remains elevated
- Inadequate sealing of slab-wall joint or sump pit — air leakage short-circuits the depressurization
- Fan installed inside the conditioned envelope without proper sealing — the fan pressurizes the home if any leak develops on the suction side
- Roof termination too close to a fresh-air intake or window — exhausted radon re-enters the home
- Long-term fan failure without homeowner detection — annual or biennial re-testing catches this
The standards-of-practice and certification framework is designed to prevent these failures, but verification testing is the homeowner’s check.
Reading the manometer correctly
Every active mitigation system includes a U-tube manometer mounted on the vertical run of pipe. The manometer is a clear plastic tube filled with red or blue fluid that displays the pressure differential between the suction-side pipe and the surrounding room. When the fan is running and the system is properly configured, the fluid in the suction leg is depressed below the room-side leg by typically 1.0 to 2.0 inches of water column — a visible offset that indicates active depressurization.
Homeowners should check the manometer monthly. The fluid levels should match the position shown in the installer’s commissioning photograph. If the fluid levels equalize, the fan has likely failed and the system needs service. If the offset becomes much larger over time, a blockage may have developed in the suction pipe. Either condition warrants a service call. CDPHE-recognized mitigation contractors typically provide manometer-reading instructions during the installation walkthrough.
Radon-resistant new construction and the activation question
Homes built in EPA Zone 1 areas after roughly 2010 — which includes most new construction along the Front Range — typically include a passive radon-resistant rough-in installed during framing. The rough-in consists of a vapor barrier under the slab, a gravel bed, a vent-pipe stub through the slab, a continuous vent pipe routed through the home to a roof termination, and a junction box for future fan installation. The rough-in is passive — there is no fan, so the system relies on natural convection up the pipe.
For some homes, the passive rough-in is sufficient to keep indoor radon below the EPA action level. For others — especially homes on uranium-rich Pierre Shale subcrop or homes with significant foundation penetrations — post-construction testing identifies the need to activate the rough-in by installing a fan. Activation typically costs $400–800, substantially less than installing a system from scratch. Front Range homeowners with new-construction homes should test soon after move-in and activate the system if needed.
Mitigation in homes with multiple foundations
Homes with additions, walkout basements, or mixed foundation types (basement under part of the home, slab-on-grade or crawl space under another part) often require multiple suction points or multiple separate systems. The mitigation contractor’s diagnostic assessment identifies whether one suction point will produce sufficient pressure-field extension across the entire foundation footprint or whether multiple points are needed. Cost for multi-foundation homes runs $2,500–4,000 depending on the configuration.
The post-installation verification test is critical in these cases — a system that effectively depressurizes one foundation section can still leave another section with elevated indoor radon. The verification should ideally include placement of test devices in multiple rooms of the home, not just a single location.
When to call a professional
For any radon test result at or above the EPA action level of 4.0 pCi/L, hire a CDPHE-recognized NRPP or NRSB-certified mitigation contractor. For homes between 2.0 and 4.0 pCi/L, consider mitigation if young children or smokers are in the home. For new construction in EPA Zone 1 areas, ensure the builder includes the radon-resistant rough-in. The broader radon-in-Colorado context and mitigation system options are covered on the Colorado radon testing pillar and the radon mitigation methods guide.
References
- Consumer’s guide to radon reduction — U.S. Environmental Protection Agency
- Colorado radon mitigation — Colorado Department of Public Health and Environment
- Radon mitigation overview — International Association of Certified Home Inspectors
Front Range homeowners with elevated radon test results can reach a vetted local CDPHE-recognized mitigation contractor through the contact page.