Radon Mitigation in Denver

Illustration of a house with a radon vent pipe and exterior fan running up the side wall to above the roofline — Illustration

EPA recommends fixing your home if a test shows 4 pCi/L or more, and suggests considering a fix between 2 and 4 pCi/L, since no level is considered completely safe [1]. CDPHE says mitigation systems can reduce radon in any home [2].

Common system types

Sub-slab depressurization: a pipe through the basement or slab floor and a fan draw soil gas from under the slab and vent it above the roofline. CDPHE calls sub-slab (or sub-membrane, for crawl spaces) depressurization usually the most effective solution [2].
Sub-membrane depressurization: for crawl spaces, a sealed plastic membrane covers the soil and the same suction approach is applied beneath it [1][2].
Sealing: cracks and openings are sealed as part of a system, but CDPHE says sealing alone is not recommended as a stand-alone method because it's temporary and can't close every gap [2].

Denver housing and mitigation design

The Denver metro has a mix of foundation types: full and partial basements, garden-level basements, crawl spaces, slab-on-grade additions, and combinations in older homes that have been expanded over time. Homes with more than one foundation type may need more than one suction point, which is a common reason quotes differ. A licensed mitigator should inspect your foundation before quoting.

After installation

EPA recommends testing again after the system is installed and retesting periodically [1][3]. CDPHE recommends homes with mitigation systems retest every two years [4]. Systems typically include a pressure gauge (manometer) or alarm so you can see that the fan is running [3].

Hire licensed

In Colorado, radon mitigation for pay requires a state radon mitigation professional license [5]. Ask for the license number and verify it with DORA before signing.

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Common questions

What radon level needs mitigation?

EPA recommends fixing the home at 4 pCi/L or higher and considering it between 2 and 4 pCi/L.

Can I just seal the cracks?

CDPHE does not recommend sealing as a stand-alone technique; it is part of a system, not a substitute for one.

Does a new home need testing?

Yes. EPA and CDPHE recommend testing all homes, new or old.