Crawl Space and Basement Radon Systems in Northern Colorado
The right radon system for a home depends first on what sits underneath it. Foundation type, meaning what separates your living space from the soil, drives how a radon system gets built and what it costs. Across Northern Colorado, where both Larimer and Weld Counties sit in EPA Radon Zone 1, the highest-potential category, that design choice matters on nearly every home. NoCo Radon Pros is a free matching service. We do not build systems and we hold no license. Instead, we connect you with an independent, Colorado-licensed radon professional who designs the right system for your specific foundation.
Why foundation type sets the design
Radon enters a home the same way regardless of how it is built: soil gas moves from the ground into the lowest level through cracks, gaps, and the pores in concrete or bare earth. The fix is always the same idea, which is to intercept that gas below the home and vent it safely above the roof before it gets indoors. What changes is how a system reaches the soil.
Under a poured slab or a finished basement floor, there is concrete to work with, so a fan can draw gas from a single point beneath it. Over a dirt or gravel crawl space, there is no slab, so the professional you are matched with has to create a sealed surface first. That one difference, concrete versus open soil, is the main reason crawl space jobs cost more than slab jobs. Everything downstream, the labor, the materials, and the price, follows from what your house is standing on.
A high radon test result is what usually starts this conversation. Once a measurement comes back at or above the EPA action level of 4.0 pCi/L, the next question is which system your foundation calls for.
Slab-on-grade and basement homes: active sub-slab depressurization
Most homes with a concrete floor over the soil get a system called active sub-slab depressurization, or ASD. It is the workhorse of radon mitigation. A licensed installer cuts a small hole through the slab, hollows out a suction pit in the gravel or soil beneath, then runs sealed PVC pipe from that point up and out above the roofline. A continuously running inline fan keeps a slight vacuum under the slab, so soil gas is captured and vented instead of drifting up through floor cracks.
Basement homes work on the same principle, since a basement floor is simply a slab that sits lower in the ground. Because the concrete does the sealing work for you, these are the most predictable systems to price. A standard sub-slab install in Colorado usually falls in the range of $1,000 to $2,500, with about $1,500 common for a typical home. You can see the full picture in our radon mitigation cost guide.
Crawl space homes: sub-membrane depressurization
A crawl space has no slab, so a straight sub-slab system has nothing to pull against. The answer is sub-membrane depressurization. The radon professional you are matched with lays a heavy, durable plastic vapor barrier across the entire crawl space floor, then seals it carefully to the foundation walls, piers, and any penetrations. That membrane becomes the surface a fan can work under, taking the place of concrete.
With the barrier sealed, the installer ties in a pipe and fan that draw soil gas from the space beneath the membrane and vent it above the roof, exactly like a slab system does under concrete. The sealing step is where the extra work lives. A crawl space membrane has to be fitted around posts and uneven ground, then made airtight, which takes more time and material than cutting a single hole in a slab.
That labor is why crawl space systems commonly run $2,000 to $5,000, depending on the size and condition of the space. A large, damp, or awkward crawl space sits at the higher end. Learn more about how these spaces are handled on our radon mitigation overview.
Sump-based systems
Homes with an interior perimeter drain and a sump pit have a built-in advantage. A sump crock connects to the drain tile that already rings the foundation footings, which gives a radon system a ready-made network of channels under the slab. An installer can cap and seal the sump pit, then draw soil gas through the existing drain tile with a fan, often reaching more of the sub-slab area than a single suction point would.
The trade-off is that the sump lid has to be sealed airtight while still allowing the pump to do its water-management job. When it is set up correctly, a sump-based system can be an efficient way to cover a larger footprint. The licensed professional you are matched with will confirm whether your sump is a good tie-in point after inspecting it.
Mixed and multi-foundation homes
Plenty of Northern Colorado houses do not fit one clean category. Additions, split levels, and older homes remodeled over the years often combine a basement under one section with a crawl space under another, or a slab garage conversion beside a dirt cellar. These mixed foundations need a design that treats each area for what it is.
Sometimes one fan can serve the whole house through tied-in piping that reaches both a sub-slab point and a sub-membrane area. Other homes need more than one system to cover separate zones properly. There is no single template, which is exactly why the design belongs to a licensed professional who has walked your specific layout rather than a formula applied sight unseen. Whatever the configuration, the job is not finished until a post-mitigation test confirms the levels came down.
Inaccessible crawl spaces and air exchange
Some crawl spaces cannot be sealed the standard way. If a space is too shallow to enter, chronically wet, or packed with obstructions, laying and sealing a proper membrane may not be practical. In those cases the design can shift toward mechanical air exchange, using a heat recovery ventilator (HRV) or energy recovery ventilator (ERV) to dilute and exchange the air rather than depressurize the soil.
These setups involve more equipment and more labor, so they can run higher than a standard crawl space job, sometimes in the range of $5,000 to $10,000. It is not the common path, but it is the honest answer for a space that will not cooperate with a membrane. The Colorado-licensed radon professional you are matched with makes that call after seeing the crawl space in person.
Start with a test, then get matched
Every good system starts with a measurement and ends with one. A baseline radon test tells the installer what they are solving for, and a post-install test proves the system worked. Colorado licenses radon measurement and mitigation professionals through the state DORA program, so you can verify any contractor’s credentials on the DORA license lookup before work begins. That license belongs to the professional, never to this brand.
When you are ready, tell us your foundation type and your test results, and we will connect you with an independent, state-licensed local radon professional who can design a system for your home. It costs you nothing, and you can read exactly how we make money so there are no surprises.