1. Two Approaches to Radon Reduction
Radon mitigation systems come in two primary forms: passive and active. Both use the same basic concept of routing radon gas from beneath your home's foundation and venting it safely above the roofline. The critical difference is whether a fan is involved.
A passive system relies on natural air convection to move radon upward through the pipe. An active system adds a powered fan that continuously pulls radon from beneath the slab, creating reliable negative pressure under the foundation.
This distinction might sound minor, but it has a massive impact on performance. Passive systems typically reduce radon by 30 to 50 percent. Active systems achieve 95 to 99 percent reduction. For a home with dangerously high radon levels, that gap can be the difference between safe and unsafe indoor air.
2. How Passive Systems Work
A passive radon system consists of a PVC pipe that runs from a collection point beneath the foundation slab, through the interior of the home (typically through closets or wall cavities), and exits through the roof. There is no fan, no motor, and no electricity involved.
The system works through natural thermal convection. Air inside the pipe is warmer than the surrounding soil air, especially in winter. Warm air rises, creating a gentle upward draft that pulls some radon from beneath the slab and vents it above the roof.
Passive Advantages
- No electricity cost (zero operating expense)
- No fan noise
- No mechanical parts to maintain or replace
- Already installed in many newer Georgia homes
- Provides some baseline radon reduction
Passive Limitations
- Only 30 to 50 percent radon reduction
- Performance varies with weather and season
- Convection weakens in mild or warm weather
- May not reduce radon below 4 pCi/L in many homes
- No consistent negative pressure under slab
Many new-construction homes in Georgia are built with passive radon systems already in place, sometimes called radon-resistant new construction (RRNC). These homes include a gas-permeable layer beneath the slab, sealed foundation penetrations, and a passive vent pipe. The idea is that if radon testing later shows elevated levels, the system can be easily upgraded to active.
3. How Active Systems Work
An active radon system uses the same basic piping layout as a passive system, but adds a radon fan (also called an inline fan or radon exhaust fan) to the pipe. This fan runs continuously, 24 hours a day, 365 days a year.
The fan creates consistent sub-slab depressurization, meaning it maintains constant negative pressure beneath your foundation. Instead of relying on gentle convection, the fan actively pulls radon-laden soil gas from under the slab and exhausts it above the roofline where it dissipates harmlessly into the outdoor air.
This mechanical suction is what makes active systems so effective. The fan does not care about outdoor temperature, wind direction, or season. It pulls radon out consistently, which is why active systems achieve 95 to 99 percent reduction in most homes.
Active System Operating Costs
A radon fan typically costs $5 to $10 per month in electricity, similar to running a light bulb continuously. Fans are designed to last 10 to 15 years before needing replacement, and replacement fans cost $150 to $300. The total annual operating cost is roughly $60 to $120 per year for reliable radon protection.
Most active systems also include a U-tube manometer or an alert indicator mounted on the pipe. This simple device lets you confirm at a glance that the fan is running and creating proper suction. If the liquid levels in the manometer are uneven, your system is working. If they are level, the fan may need attention.
4. Side-by-Side Comparison
| Feature | Passive System | Active System |
|---|---|---|
| Radon Reduction | 30 to 50% | 95 to 99% |
| Power Source | None (natural convection) | Electric fan (continuous) |
| Operating Cost | $0 per year | $60 to $120 per year |
| Seasonal Consistency | Varies significantly | Consistent year-round |
| Maintenance | Virtually none | Minimal (check manometer) |
| Noise Level | Silent | Low hum (barely noticeable) |
| Best For | New construction (built-in), low radon areas | Confirmed radon above 4 pCi/L |
The comparison makes the performance gap clear. While passive systems are better than nothing, they are not a reliable solution for homes with confirmed radon problems. If your home tests above 4 pCi/L, an active system is the standard recommendation from the EPA and radon professionals across the industry.
5. Converting Passive to Active
If your home already has a passive radon system, the good news is that converting to active is one of the simplest and most cost-effective home improvements you can make. The infrastructure is already in place. All that is needed is adding a fan and ensuring proper electrical connections.
Radon testing confirms elevated levels
A professional test shows your home is at or above 4 pCi/L despite having a passive system in place.
A radon fan is installed in the pipe
The fan is typically placed in the attic space or on the exterior of the home. A section of the existing PVC pipe is cut, and the fan is connected inline.
Electrical connection is made
The fan needs a dedicated electrical outlet. If one is not nearby, a licensed electrician runs a circuit to the fan location.
System is tested and verified
A manometer is installed, the system is activated, and a follow-up radon test confirms that levels have dropped below 4 pCi/L.
The entire conversion typically takes just a few hours and costs between $500 and $1,000. Compare that to a full active system installation ($1,200 to $2,500 for homes without any existing infrastructure), and you can see why building passive systems into new homes is such a smart investment, even if they are not fully effective on their own.
6. Which System Does Your Home Need?
The answer depends on your situation and your radon test results. Here is a practical guide.
Passive May Be Enough If...
- Your home tests below 2 pCi/L consistently
- You are in a low-radon area with minimal geological risk
- Your home is new construction with full RRNC features
- You plan to test regularly and upgrade if levels rise
You Need Active If...
- Your home tests at or above 4 pCi/L
- Your passive system is not reducing levels enough
- You want consistent, year-round protection
- You are in a known high-radon area of Georgia
- You have a basement or slab-on-grade foundation
Do Not Assume Your Passive System Is Working
Many homeowners in Georgia assume the radon pipe they see going through their attic means they are protected. Without a fan, that pipe provides only partial protection. The only way to know if your passive system is reducing radon to safe levels is to test your home. If results are above 4 pCi/L, upgrading to active is the clear next step.
7. Cost Breakdown
One of the most common questions homeowners ask is how much each option costs. Here is a realistic breakdown for homes in the Atlanta metro area.
Passive System (New Construction)
Cost: $300 to $600 when included during construction. This covers the gas-permeable gravel layer, vapor barrier, sealed penetrations, and PVC vent pipe. Many builders in Georgia now include this as a standard feature, especially in counties with known radon risk.
Converting Passive to Active
Cost: $500 to $1,000. This includes the radon fan, installation labor, electrical work, and a manometer. It is by far the most cost-effective way to get active radon protection, because the hardest part (running the pipe through the house) is already done.
Full Active System (Retrofit)
Cost: $1,200 to $2,500 for most homes. This covers everything: drilling through the slab, installing the sub-slab suction point, running PVC pipe to the roofline, installing the fan and electrical connection, sealing foundation cracks, and the manometer. Larger homes or those with complex foundations may cost more.
Ongoing Costs (Active System)
Electricity: $60 to $120 per year. Fan replacement: $150 to $300 every 10 to 15 years. Periodic radon retesting: $150 every 2 years. Total annual cost of ownership is roughly $100 to $200 per year for continuous radon protection.
