Radon mitigation in Denver: what the system involves and how to finish around it

Radon mitigation in a Denver basement usually means soil depressurization. A fan pulls soil gas from under the slab into a vent pipe and sends it outside, and the cracks and sump lid get sealed.¹ Most Colorado installs take four to eight hours in one visit.¹ Get it done and retested before you frame. The pipe, the fan and the sump lid decide where your walls, soffits and access panels go.

TL;DR

• Colorado's state health department links radon to about 500 lung cancer deaths in the state each year. A test in your own basement is the only number that counts.²
• The EPA recommends mitigation at or above 4.0 picocuries per liter (pCi/L), and many mitigated homes end up below 1.0.¹
• Your install price gets set after a mitigation company sees your foundation. Running cost is small, since a radon fan draws 42 to 85 watts.³
• The order is test, mitigate, retest, then frame. Retest again after the finish, because finishing can change the pressure under the house.¹
• Plan the pipe chase, the manometer view and the sump access panel on paper before framing starts. Keep the fan away from any basement bedroom.³

Are radon levels high in Denver?

Your own test is the only reliable answer for your house. Colorado's state health department runs a radon program and says radon causes about 500 lung cancer deaths in Colorado each year.² The gas comes from uranium breaking down in the soil and gets into homes from the ground below.²

A neighbor's low result tells you nothing about your slab. The EPA recommends mitigation for homes that test at or above 4.0 pCi/L.¹ If your result is at or over that line, plan the system before you plan the finish.

Levels also move over time. Soil shifts, foundations settle and airflow inside the house changes, so a home that once tested low can test higher years later.¹ Front Range ground is part of that story. The Colorado Geological Survey calls swelling soil a common and sometimes serious problem in Colorado that can damage houses slowly over time.⁴ Foundations that move develop small cracks, and cracks are entry points for radon.¹

Timing matters for the test itself. One Colorado radon company names fall and winter as the best time to test, when homes are closed up.¹ If your short test came back high, ask a radon professional whether to confirm it before you commit to a layout.

What does a radon mitigation system involve?

A basement system has a few fixed parts. There's a suction point drilled through the foundation, a sealed vent pipe, a fan and sealing on the sump lid, cracks and utility openings.¹ The fan runs all the time.³ It creates negative pressure under the slab, so radon goes up the pipe instead of through the floor.¹

Here's what each part does and what it means once you start finishing.

Installation is usually one visit. For most Colorado homes it takes four to eight hours.¹ After that comes a post-mitigation test. One Front Range company tells customers to wait at least 72 hours before setting the test kit and to finish the test within 30 days of the install.³ Set it in the lowest livable space, in the middle of the room, at least 2 feet off the floor and away from drafts.³

One Colorado mitigation company reports that professionally installed systems often cut radon by 80 to 99 percent.¹ Treat that as a company's claim. Your post-test is the proof for your house.

Two side effects are worth knowing before you finish. The system pulls moisture vapor out from under the slab along with radon. In a cold winter that condensation can freeze in the vent pipe and clog it for a while.³ And if you hear gurgling at the suction point, there may be water under the slab. One mitigation company says the fan can't pull that water up, but you'll likely need waterproofing.³ Sort that out before any drywall goes in.

Radon system design and installation is a job for a radon mitigation professional. For the full picture of system types, read how radon mitigation systems work.

How much does radon mitigation cost in Denver?

The install price gets set after a mitigation company looks at your foundation. Soil type, foundation design and layout all change how radon moves, and the system gets designed around them.¹ So the system is priced at your estimate. For the wider view on pricing, see what radon mitigation costs.

What you can pin down is what pushes a quote up or down.

• The age and condition of the house. Older homes tend to have more foundation cracks, mixed materials and past additions, which means more entry points to seal.¹
• Waiting. More cracks, moisture problems or a worn crawl space can make the install more complex later.¹
• Add-ons for noise and cold. One Front Range company offers a muffler above the fan, a fan cover and a copper defroster for ice in the pipe.³
• What the result warranty covers. That same company warrants levels below 4.0 pCi/L in livable areas for ten years on systems with a fan moisture guard, unless the contract says otherwise.³ Terms vary, so read yours.

Running cost is easier. Radon fans typically draw 42 to 85 watts. To get cost, multiply the wattage by hours used per day, divide by 1,000 and multiply by your per-kWh rate.³ For a fan running all day, that works out to about 1.0 to 2.0 kWh a day, or roughly 368 to 745 kWh a year. Multiply that by the rate on your electric bill.

Colorado's health department also lists a Low Income Radon Mitigation Assistance program (LIRMA).² If money is tight, check whether you qualify before you pay out of pocket.

The radon system gets its own quote, separate from the finish. A metro Denver basement finish runs $30,000 to $90,000 (checked September 2026). You can see what basement finishing costs in Denver and where the pipe chase and soffits show up in that budget.

How do the fan, pipe and sump affect framing and ceilings?

They set fixed points your framing has to work around. An inside pipe run needs a chase or closet, the manometer has to stay in view and the sump lid needs an access panel. The fan belongs away from bedrooms and living rooms.³ Draw all four on your layout before anyone orders studs.

Suction point and manometer

The manometer sits around eye level on the extraction pipe. Its starting reading is recorded on the system at install.³ One Denver-area company tells owners to call if the reading moves above 3.5 or below 0.5. A flat reading means the gauge sees no suction at all.³ You can't check any of that through drywall. Leave the pipe exposed in a utility room, or have your contractor frame a chase with a clear cutout or small door at gauge height.

Pipe routing and ceiling height

The route decides how much ceiling you lose. An exterior route keeps the pipe outside, run along a corner or behind a downspout.¹ An interior route climbs through a closet or chase to the attic. Any horizontal run under the joists becomes a soffit, which lowers the ceiling in that strip. Try to line the pipe up with ductwork you're already boxing in, or land the chase in a storage room or mechanical room. If you plan to move ducts to share a soffit, the City of Denver requires a permit for new or rerouted ductwork.⁵

Fan placement and noise

No radon fan is silent. Expect a hum like a bathroom vent fan.³ One mitigation company steers fans away from bedrooms and living rooms and toward spots near the A/C unit or up in the attic.³ If a basement bedroom is on your plan, keep the pipe chase off its walls. Vibration can also travel through mounting screws and brackets into the walls.³ Ask how the pipe will be strapped so the hum doesn't carry into new framing.

Sump pit and lid

A sealed sump lid is part of the system.¹ Systems can draw from the sump pit too.³ The pump still needs service, so frame an access door or removable panel over the pit. Keep carpet and flooring off it.

Floating walls and slab movement

Swelling soil is a common problem in Colorado.⁴ A floating wall is built for that movement. It's framing with a slip joint at the bottom, so a moving slab doesn't push on the floor above. The radon pipe goes straight through the slab, so the pipe moves with the slab. Ask your contractor to leave clearance where the pipe passes through framing so movement doesn't bind it.

Power for the fan

The fan's outlet or switch has to stay reachable after the walls close. The converter box on newer fans gets warm because the system runs 24/7. It has an automatic shut-off if it overheats.³ Leave it in an open, reachable spot outside any sealed cavity. Hire a licensed electrician for any new circuit. The City of Denver requires permits for new or relocated electrical fixtures.⁵

Mitigate, retest, then frame

Basement Remodeling Co.'s planning rule is radon settled before framing. Test first. Install the system and run the post-mitigation test. Then frame, insulate and close the walls. Retest after the finish, because renovations such as basement finishing can change the pressure under the house.¹ After that, retest every two years.¹

1. Test. Use a result from the lowest livable level.
2. Mitigate. A radon mitigation professional designs and installs the system.
3. Post-test. Confirm the level dropped before you build over anything.
4. Plan the finish. Mark the chase, the manometer view, the sump panel and the fan outlet on the layout.
5. Build. Your contractor pulls the permit and books the inspections.
6. Retest. Check again once the finish is done, then every two years.

In the City of Denver, the interior remodel guidance covers basement finishes.⁵ Permits are required for changes to the floor plan, new or rerouted ductwork and new or relocated electrical or plumbing fixtures.⁵ Outside the city, your own city or county sets its permit rules. Denver also advises homeowners to hold the final payment until building inspections have been approved.⁶ The details are in our guide to basement permits in Denver.

When the system is in and the retest is back, get a written quote for finishing your basement in Denver. The request goes to one vetted, licensed basement contractor, who books a free on-site estimate and gives you a written, itemized quote. For the wider Colorado picture on soils, permits and moisture, see our guide to finishing a basement in Colorado.

What a good quote shows

You'll get two quotes, one for the radon system and one for the finish, and each should name the parts that affect the other. The mitigation quote shows the suction point, pipe route, fan location, sealing and post-test. The finishing quote shows how the chase, the sump access and the manometer view are handled.

The radon system quote

• Where the suction point, pipe route and fan will go, ideally on a sketch.
• Sealing of the sump lid, cracks and utility openings.¹
• The post-mitigation test and who pays for it. One Front Range company includes a charcoal test kit with each install.³
• The warranty. One company puts all warranty terms on the signed proposal.³ Check what's covered for the fan and for the radon result.
• Any add-ons, such as a muffler, fan cover or defroster.³

You'll have options. BBB's accredited listing showed 44 radon mitigation results near Denver in September 2026.⁷ Ask each company which radon certification its installers hold. Denver's own advice for hiring any contractor applies too: ask for references, check the insurance is current and never pay cash.⁶

The finishing quote

• A framed chase or closet for an interior pipe run, with its size and location.
• Any soffit that lowers the ceiling, and by how much.
• An access panel or door over the sump pit.
• A visible manometer, either exposed or behind a cutout.
• A reachable outlet or switch for the fan.
• A retest once the finish is complete.

If your basement is already finished and tested high, the system gets threaded through existing walls instead. The same checks apply to remodeling a finished basement in Denver. You can also read what a full basement finish covers, find a basement contractor by ZIP code or start from our Denver page.