A radon mitigation system is installed in homes and buildings to reduce radon gas levels and protect occupants from radon exposure. Radon is a radioactive gas that originates from the natural decay of uranium in soil and rock. It enters homes through cracks and openings in the foundation and can accumulate to dangerous levels in indoor air. Long-term radon exposure is the second leading cause of lung cancer after smoking. Having a radon mitigation system is important for reducing this health risk.
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Overview of radon mitigation systems
Radon mitigation systems work by creating a “ventilation” system under the home’s foundation. The systems use PVC piping and an inline fan to draw radon gas from under the home’s foundation and vent it above the roofline where it can dissipate harmlessly. This reduces pressure under the home and prevents radon from being drawn inside.
The main components of a radon mitigation system include:
- PVC piping running from below the home’s foundation to above the roofline
- An inline fan mounted at the roofline to provide suction
- A junction box to house any electrical components
- Various PVC fittings to connect the piping
- A radon vent cap to disperse the radon above the home
The inline fan creates a vacuum effect, drawing radon up from the ground beneath the home’s foundation. The radon is then vented through the PVC piping system up and out above the roofline where it is quickly diluted by outdoor air. This significantly reduces radon levels inside the home, typically by up to 99%.
Piping layout
The PVC piping in a radon mitigation system runs from a suction point below the home’s foundation slab up through the house and roofline. Here are some key details on the piping layout:
- The starting point is usually a suction pit installed in the gravel layer underneath a concrete slab foundation. This draws radon directly from the soil.
- For homes with crawlspaces, piping will run from the soil of the crawlspace up through the house.
- Piping routes up through interior walls, utility closets, or conditioned space.
- Piping usually exits through the roofline of the home.
- All joints are glued and fitted properly to form an airtight seal.
The piping often takes the shortest and most direct route from the suction point up through the home to the roofline. Attics provide an easy access point before exiting above the roof. Piping should be installed against interior walls for aesthetic reasons. All piping connections must be completely sealed using primer and glue to prevent leaks.
Inline fan unit
The inline fan unit provides the suction power to draw radon gas from beneath the foundation. Key facts about the inline fan include:
- Usually mounted and secured in the attic or on the exterior roofline.
- Requires an electrical power source; hardwired to junction box.
- Powerful enough cubic feet per minute (CFM) rating to provide sufficient suction.
- Often rated for continuous operation – runs 24/7.
- Makes humming or whirring noise when switched on.
- Includes warning light to indicate operational problems.
The inline fan requires a sufficiently high CFM rating (around 150 to 300 CFM) to create enough suction through the piping system. It needs to run continuously to maintain constant suction. Fans are mounted securely given their vibrations and typically rated for long-term, continuous operation. Always install the fan in an accessible location for any needed maintenance.
Junction box
The junction box houses any electrical components for powering the inline fan. Details include:
- Usually mounted in attic near inline fan.
- Contains electrical input wires and connectors.
- May house a transformer to step down voltage.
- Has an on/off switch to control power to fan.
- Often includes alarm light to indicate problems.
- Must be properly grounded and adheres to local codes.
A licensed electrician handles wiring the junction box to provide power for the radon mitigation system. The box should be accessible in case service is needed on the fan unit. Having an alarm light and on/off switch at the box provides important controls over the fan operation.
PVC vent pipes and fittings
The right PVC pipes and fittings are vital for creating a sealed, airtight system. Key points about the PVC components include:
- Piping often 3” or 4” diameter PVC schedule 40.
- PVC elbows, tees, adapters used to connect piping.
- Pipe sections glued together using PVC primer and cement.
- Waterproof, airtight PVC cement critical at all joints.
- Rubber boots used for any underground pipe connections.
- Concentric PVC reducers transition piping sizes.
All PVC piping and accessories must meet the schedule 40 rating for durability. Carefully gluing all joints is critical to eliminate any air leaks. A combination of 45° and 90° elbows allows for turns in the piping route. Adapters, reducers, and tees connect the various pipe diameters. Any underground sections use waterproof rubber boots to seal connections.
Radon vent cap
A special PVC vent cap installs over the end of the radon discharge pipe above the roofline. Key features include:
- Caps mount over final PVC pipe.
- Prevents rain, debris from entering the piping.
- Allows radon gas to harmlessly vent upward.
- Usually includes mesh screen to prevent pest entry.
- May have decorative plastic housing for aesthetic purposes.
- Requires proper seal around pipe for waterproofing.
The vent cap fitting provides a critical function to allow radon venting while keeping rain and pests out of the piping system. Make sure the cap and final piping connections are properly sealed against moisture. Having a secure mount and proper discharge height are also important for optimizing the radon venting.
Suction point
A suction point is required to draw radon gas from underneath the home foundation. Key aspects include:
- Installed below concrete slab foundation or in soil of crawlspace.
- Often consists of a PVC “T” fitting with perforated suction pipe.
- May use gravel and a drain tile to enhance soil gas collection.
- Requires sealed, airtight connections at entry points.
- Needs proper depth and location for effective gas collection.
Proper placement of the suction point allows it to actively collect radon from the surrounding soil. For concrete slab homes, the suction point with perforated piping installs in a gravel layer underneath. In crawlspaces, perforated piping can buried in the soil. Any entry points where piping penetrates foundation walls must be completely sealed.
Diagnostic testing
Various diagnostic tests help confirm that the radon mitigation system is working correctly. This may include:
- Initial short-term radon measurements upon installation.
- Follow-up long-term radon testing after 1 month and 1 year.
- Smoke testing by professionals to check for leaks.
- Pressure field extension testing below foundation.
- Checking inline fan operation and wiring.
Short and long-term radon measurements, with test kits or professional monitors, should show radon reductions of up to 99% if the system is properly installed. Experts can diagnose the system using smoke or pressure testing methods. Routinely checking the fan function also helps confirm proper system operation and performance.
Maintenance needs
Like any mechanical system, radon mitigation systems do require periodic maintenance for best performance. This includes:
- Checking/replacing inline fan every 5-8 years.
- Cleaning fan components of any dust buildup.
- Confirming fan electrical wiring remains intact.
- Ensuring PVC piping has no leaks or detachments.
- Sealing any new cracks or openings in foundation.
- Re-testing radon levels every 2 years.
The inline fan has a finite lifespan and will need replacement at some point. Visually inspecting the system components and testing for radon ensures that the mitigation system continues working properly. Any foundation changes also need to be checked so they don’t alter radon entry points.
Professional installation
Proper installation by certified radon mitigation professionals is recommended. The benefits of professional installation include:
- Knowledge of codes compliance and safety practices.
- Accurate system design and layout.
- Quality workmanship on sealing, fittings, electrical.
- Right inline fan sizing to achieve sufficient suction.
- Optimal placement of suction piping.
- Testing and adjustments to ensure radon reduction.
There are health and safety risks if radon piping leaks or is not properly sealed. Professionals have the skills to size components appropriately and diagnose the system to confirm functionality. This provides peace of mind that the radon mitigation system is working effectively to reduce levels below EPA action thresholds.
Conclusion
In summary, a radon mitigation system requires specific components and professional installation in order to effectively reduce radon. This includes durable PVC piping, an adequately powered inline fan, sealed connections, proper suction points below the foundation, and venting above the roofline. With the right materials, layout, and fan power, radon mitigation systems can successfully lower indoor radon for improved home health and safety.