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How Is Radon Mitigated?

Radon mitigation primarily involves actively venting radon gas from beneath the building before it can enter, effectively reducing indoor radon levels. This often utilizes a system that collects radon from the soil and safely exhausts it outside, away from windows and other openings.

Understanding Radon and Its Risks

Radon is a naturally occurring, colorless, odorless, and tasteless radioactive gas that forms from the decay of uranium in soil, rock, and water. While it’s present everywhere, radon becomes a health hazard when it accumulates in enclosed spaces like homes. The Environmental Protection Agency (EPA) estimates that radon is the leading cause of lung cancer among non-smokers and the second leading cause overall in the United States. The primary pathway for radon entry into buildings is through cracks and openings in foundations, walls, and around pipes. Because prolonged exposure to elevated radon levels poses a significant health risk, radon testing and mitigation are crucial steps in ensuring a safe living environment.

Mitigation Techniques: Reducing Radon Levels

The most common and effective radon mitigation technique is sub-slab depressurization (SSD). This system creates a vacuum beneath the concrete slab foundation, drawing radon gas away from the house before it enters.

Sub-Slab Depressurization (SSD)

SSD involves installing one or more suction points beneath the foundation slab. This is typically done by drilling a hole through the slab and removing soil beneath it to create a small cavity. A PVC pipe is then inserted into the hole, sealed with caulk, and connected to a fan that draws air from beneath the slab. The radon-laden air is then vented outside, usually above the roofline, where it is diluted in the atmosphere.

Active vs. Passive SSD: An active SSD system uses a fan to actively draw air. A passive SSD system relies on natural convection, which is generally less effective and less commonly used. Active systems are recommended in most cases.
System Monitoring: U-tube manometers are often installed to visually verify that the system is functioning properly and maintaining negative pressure under the slab. Regular maintenance, including fan checks, is essential.

Other Mitigation Methods

While SSD is the most common and effective, other mitigation techniques may be necessary or more suitable depending on the building’s construction and radon entry pathways.

Sub-Membrane Depressurization (SMD): Used in crawl spaces, SMD involves sealing the crawl space floor with a plastic membrane and then using a fan to draw air from beneath the membrane, venting it outside.
Block Wall Depressurization (BWD): This technique applies to homes with hollow-block foundations. It involves sealing the top of the block wall and then drawing air from inside the blocks to vent radon.
Sealing Cracks and Openings: While sealing alone rarely reduces radon levels to acceptable levels, it can be a valuable supplement to other mitigation methods. Sealing cracks, joints, and openings in the foundation and walls can reduce the amount of radon entering the home.
Soil Depressurization outside the Foundation (Exterior Depressurization): Installing a suction pit outside the foundation wall and connecting it to a vent pipe and fan.

Selecting a Mitigation System

The best mitigation system for a particular home depends on several factors, including the construction type, foundation type, soil permeability, and radon levels. Consulting with a qualified and certified radon mitigation professional is crucial to determine the most appropriate and effective solution. Professionals will conduct thorough testing, assess the building, and design a system tailored to the specific needs of the home. Look for professionals certified by the National Radon Proficiency Program (NRPP) or the American Association of Radon Scientists and Technologists (AARST).

Long-Term Considerations

Radon mitigation is not a one-time fix. Systems require ongoing monitoring and maintenance to ensure their continued effectiveness. Regular radon testing (every two years) is recommended, even after mitigation, to confirm that levels remain below the EPA’s action level of 4 pCi/L (picocuries per liter). The fan in an active SSD system typically has a lifespan of 5-10 years and will need to be replaced periodically.

Frequently Asked Questions (FAQs)

FAQ 1: What is the EPA action level for radon?

The EPA recommends taking action to mitigate radon when levels reach or exceed 4 picocuries per liter (pCi/L) of air. Even levels below 4 pCi/L pose some risk, and you may still want to consider mitigation.

FAQ 2: How much does radon mitigation cost?

The cost of radon mitigation varies depending on the complexity of the system and the local market. Generally, expect to pay between $800 and $2,500 for a typical sub-slab depressurization system. More complex situations may require additional costs.

FAQ 3: Can I mitigate radon myself (DIY)?

While DIY radon mitigation kits are available, it’s strongly recommended to hire a certified professional. Proper design and installation are crucial for effectiveness, and a poorly installed system may not adequately reduce radon levels. Incorrect installation can also lead to other problems, such as backdrafting of combustion appliances.

FAQ 4: How long does radon mitigation take?

The installation of a sub-slab depressurization system typically takes one day. More complex mitigation projects may require additional time.

FAQ 5: Will radon mitigation affect my home’s value?

Radon mitigation is generally considered a positive feature that can increase a home’s value by addressing a potential health risk. Disclosure of radon testing and mitigation is typically required during real estate transactions.

FAQ 6: Is radon mitigation noisy?

A properly installed and maintained radon mitigation system should be relatively quiet. The fan motor may produce a low hum, but it should not be disruptive. Noise can be minimized by selecting a quiet fan model and isolating the fan from the structure.

FAQ 7: Will radon mitigation affect my energy bills?

The fan used in an active SSD system consumes a small amount of electricity. The increase in energy costs is typically minimal, often less than $50 per year.

FAQ 8: What if my home has a crawl space?

Radon mitigation in homes with crawl spaces often involves sub-membrane depressurization (SMD). Sealing the crawl space and creating a negative pressure beneath the vapor barrier can effectively reduce radon levels.

FAQ 9: Can radon levels be reduced permanently?

Radon levels can be effectively and permanently reduced through proper mitigation. However, it’s crucial to periodically re-test to ensure the system continues to function correctly. Soil conditions and building structures can change over time, potentially affecting radon levels.

FAQ 10: Where can I find a qualified radon mitigation professional?

You can find qualified radon mitigation professionals certified by the National Radon Proficiency Program (NRPP) or the American Association of Radon Scientists and Technologists (AARST). These organizations maintain databases of certified professionals in your area.

FAQ 11: Does radon testing need to be done before mitigation?

Testing is essential before mitigation. Testing determines the baseline radon levels and informs the design of the appropriate mitigation system. Post-mitigation testing confirms the system’s effectiveness.

FAQ 12: What happens after radon mitigation is complete?

After mitigation, it’s important to conduct a follow-up radon test to verify that the system has successfully reduced radon levels to below the EPA’s action level. Regular monitoring of the system, including the fan and manometer, is also recommended. Consider a re-test every two years to ensure continued effectiveness.