Mitigation · 8 min read
Radon Fans Explained
How radon fans are chosen, why fan curves matter, what determines noise and energy use, and how long a radon fan typically lasts.
The fan is the engine of a mitigation system and its only moving part. It is also the component most often chosen badly, because selecting one correctly requires measurement rather than habit.
The right fan is the smallest, quietest unit that delivers the vacuum the soil actually demands.
Understanding the fan curve
Every radon fan has a performance curve showing airflow at various static pressures. As resistance rises, airflow falls, and each model traces a different shape.
Some fans are designed for high suction against tight soil at low airflow. Others move large volumes of air against little resistance, suiting gravel or coarse alluvium. A fan operating far from its intended point on the curve is inefficient, noisy, or ineffective.
Why oversizing is a real problem
A bigger fan sounds like insurance. In practice, an oversized fan in a tight-soil application pulls hard against a restriction, generating noise and consuming energy without materially improving vacuum at the far corners.
In a permeable-soil application, an oversized fan pulls large volumes of conditioned air down through slab cracks, raising heating and cooling costs while adding little radon benefit.
Noise
Noise complaints trace to a short list of causes.
- An oversized fan for the measured conditions
- Undersized pipe creating high air velocity
- Rigid mounting that transmits vibration into framing
- Fan placement on a wall shared with a bedroom
- Sharp fittings creating turbulence near occupied space
Energy use
Radon fans draw modest continuous power, commonly in the range of a small incandescent bulb, which lands in the low single digits of dollars per month for most homes.
Newer fan designs deliver the same performance at lower wattage, so a replacement fan often costs less to run than the unit it replaces.
Lifespan and failure
Fans are rated for continuous duty with a service life measured in years, and warranties commonly run around five years. Real-world life depends heavily on environment: a shaded exterior mount in a coastal climate typically outlasts one in a 140-degree inland attic.
Failure is usually gradual, beginning with bearing noise, then intermittent operation, then a stop. Because it is silent when it stops, the manometer is the only reliable indicator for most households.
Where the fan is mounted
Always outside the conditioned envelope. Downstream of the fan the pipe is under positive pressure, so any joint leak in that section pushes radon out. If the fan is in a basement or closet, that leak goes into the house.
Attic and exterior wall mounting are the two acceptable options, with attic placement offering better weather protection and exterior mounting offering easier service and cooler operating temperatures.
Key takeaways
- Fan selection should come from measured static pressure and airflow.
- Oversizing causes noise and energy waste without better results.
- Fans must be mounted outside the conditioned space.
- Manometer checks are the practical way to catch silent failure.