Denver Dwellings: Radon Hiding In Your Basement?

By Franklin Everett Shaw

January 3, 2026

The air in your Denver home might be hiding a silent threat: radon. This invisible, odorless gas is a naturally occurring byproduct of uranium decay in the soil, and it can seep into homes through cracks in the foundation, gaps around pipes, and other entry points. While radon is present across the United States, Denver’s unique geological makeup, coupled with specific building practices, makes it a hotspot for elevated radon levels. Ignoring this issue isn’t just a gamble with your health; it can also impact your property value and create legal headaches when you decide to sell.

Denver’s high radon risk stems from its location along the Front Range, where the soil is rich in granite and shale, both known to contain uranium. This means that many Denver neighborhoods, from Stapleton to Wash Park, are built on ground that naturally emits radon. Furthermore, the freeze-thaw cycle common in Colorado can create cracks in foundations, providing easy pathways for the gas to enter your home.

So, what can a Denver homeowner do? You have two primary options: DIY testing and mitigation, or hiring a certified professional. Let’s break down the DIY approach first.

DIY radon testing is relatively straightforward and inexpensive. You can purchase a short-term radon test kit at most hardware stores in Denver, like Home Depot or Lowe’s, or online. These kits typically involve placing a collection device in the lowest lived-in level of your home (usually the basement) for a specified period, typically 2-7 days. After the testing period, you seal the device and mail it to a lab for analysis.

However, DIY testing has its limitations. Accuracy can be affected by factors like improper placement of the device, fluctuating weather conditions, and even the homeowner’s behavior (opening windows during the test period, for example). For instance, if you’re testing during a particularly windy week in Denver, the pressure changes could artificially inflate or deflate your radon readings.

A more reliable option is a long-term test kit, which measures radon levels over 90 days or more. This provides a more accurate average radon concentration, minimizing the impact of short-term fluctuations. You can find these kits online or through the Colorado Department of Public Health and Environment (CDPHE).

If your DIY test reveals radon levels at or above the EPA action level of 4 picocuries per liter (pCi/L), mitigation is strongly recommended. This is where things get more complex. While some homeowners might be tempted to tackle radon mitigation themselves, it’s generally best left to the professionals, especially in Denver’s unique environment.

Why? Because effective radon mitigation requires a deep understanding of building construction, soil composition, and ventilation systems. A poorly installed mitigation system can be ineffective, or even worse, create new problems like backdrafting of combustion appliances.

That being said, understanding the basics of radon mitigation can empower you to make informed decisions when hiring a contractor. The most common mitigation technique in Denver is sub-slab depressurization (SSD). This involves installing a PVC pipe through the foundation slab and connecting it to a fan that draws radon gas from beneath the slab and vents it safely above the roofline.

The effectiveness of SSD depends on several factors, including the permeability of the soil beneath your foundation. Denver’s clay-rich soil can be less permeable than sandy soil, requiring more strategic placement of the suction point and a more powerful fan.

Here’s a step-by-step overview of what a professional radon mitigation installation typically involves in Denver:

1. Assessment: A certified contractor will conduct a thorough inspection of your home to identify potential radon entry points and assess the soil conditions.
2. System Design: Based on the assessment, the contractor will design a customized mitigation system, taking into account the size and layout of your home, the type of foundation, and the soil permeability.
3. Installation: The contractor will install the PVC piping, fan, and any necessary sealing materials. The fan is typically located in an attic, garage, or outside the house.
4. Sealing: Cracks and openings in the foundation walls and slab will be sealed to prevent radon from entering the home through other pathways.
5. Testing: After installation, the contractor will conduct a post-mitigation radon test to ensure the system is effectively reducing radon levels below the EPA action level.

Choosing a qualified radon mitigation contractor in Denver is crucial. Look for contractors certified by the National Radon Proficiency Program (NRPP) or the American Association of Radon Scientists and Technologists (AARST). These certifications ensure that the contractor has the necessary training and expertise to install a safe and effective mitigation system.

Before hiring a contractor, get multiple bids and ask for references. Check their licensing and insurance status with the Better Business Bureau. Don’t be afraid to ask detailed questions about their experience, the types of systems they install, and their warranty policies.

Here’s a checklist to use when evaluating radon mitigation contractors in Denver:

• Are they certified by NRPP or AARST?
• Do they have liability insurance and workers’ compensation insurance?
• Can they provide references from previous clients in the Denver area?
• Do they offer a warranty on their work?
• Do they provide a detailed written estimate?
• Do they explain the mitigation process clearly and answer all your questions?
• Do they use high-quality materials and equipment?
• Do they follow EPA and CDPHE guidelines for radon mitigation?

The cost of professional radon mitigation in Denver typically ranges from $1,200 to $2,500, depending on the complexity of the installation. Factors that can affect the cost include the size of your home, the type of foundation, the soil conditions, and the location of the fan.

While this might seem like a significant investment, it’s important to consider the long-term health benefits and the potential impact on your property value. A home with a radon mitigation system is more attractive to potential buyers, and it can also protect your family from the risks of radon exposure.

Finally, it’s crucial to understand Colorado’s radon disclosure laws when selling your property. Colorado law requires sellers to disclose any known radon hazards to potential buyers. This includes providing information about any radon tests that have been conducted and any mitigation systems that have been installed.

Failure to disclose known radon hazards can result in legal liability. Therefore, it’s always best to be transparent about radon issues and to provide buyers with the information they need to make informed decisions.

In conclusion, addressing radon in your Denver home is a critical step in protecting your health and your investment. While DIY testing can be a useful first step, professional mitigation is often the best solution, especially given Denver’s unique geological challenges. By understanding the risks, taking proactive steps to test your home, and working with a qualified contractor, you can ensure that your home is a safe and healthy environment for you and your family. Don’t let the silent threat of radon compromise your well-being or your property value. Take action today.