Radon fan models compared: makers' own figures

The EPA describes the job simply: a fan connected to the suction pipes draws radon from below the home and releases it outdoors, while creating a negative pressure beneath the slab. Its guide to radon-resistant construction says the fan should be large enough to keep the pressure beneath the slab or membrane lower than the pressure above it. How much fan that takes depends on how easily air moves through the material under the slab.

Static pressure (inches of water column)

How strongly a fan can pull against resistance, written as inches of water column (WC, or in. w.c.). A tight soil or a long pipe run needs more of it. A maker's maximum static pressure is the most the fan can pull with no air moving.

Airflow (CFM)

Cubic feet of air moved per minute. Airflow falls as the pressure the fan works against rises, so a single maximum CFM figure is the airflow with nothing in the way, and a table of CFM at set pressures shows the curve.

For a sense of scale, the EPA's guide to radon-resistant new construction says most contractors have found 90-watt in-line fans adequate for most home styles, locations and sizes, and refers to a fan capable of moving 100 cubic feet of air per minute at one inch of water column as sufficient for most applications. That is a general figure for a new home's passive system being activated, not a sizing rule for yours; a mitigator sizes a fan from measurements taken under your slab.

Fantech says its Rn fans are designed specifically for active soil depressurization, with an air-tight housing, a UV-resistant resin housing, a UL listing for safety and outdoor use, HVI-certified fan performance and a 5-year factory warranty. It describes the Rn 1, Rn 2 and Rn 3 as covering the majority of radon mitigation jobs, and lists the Rn 1 as ENERGY STAR listed.

The two EC models differ from the rest in their motor and their dial. Fantech says the Rn 2EC and Rn 4EC have a built-in speed controller, so the installer can turn the fan down to the suction a system needs, with lower power use; its manual says to turn the dial counterclockwise with a small screwdriver to reduce speed. The brochure describes the Rn 2EC for medium suction, low flow jobs and the Rn 4EC for high suction, high flow jobs with elevated radon and poor sub-slab communication. The Rn 4EC comes with Fantech's LDVI couplings: 3-inch on item 99922 and 4-inch on item 99923.

The brochure's descriptions of the other models follow the same pattern: the Rn 1 for low suction, low flow jobs with good sub-slab communication; the Rn 2 for medium suction, low flow; the Rn 2X and Rn 3 for medium suction, medium flow with elevated radon or poor communication; and the Rn 2SL, a sealed housing with built-in condensation bypass that blends with outdoor utility boxes.

RadonAway publishes a specification table on its XP201 page covering three fans: the XP151, the XP201 and the XR261. Its figures are a range of power use, a recommended maximum operating pressure, and the typical airflow at four static pressures, which shows how each fan's airflow falls as the pressure it works against rises. RadonAway marks the XP151 and XP201 as RRNC type RF1, which it says means suitable as designated by the Reducing Radon in New Construction standard, RRNC 2.0.

RadonAway lists the XP201's features as an Eternalast polycarbonate plastic housing, a five-year limited warranty, thermal protection, a moisture-resistant J-frame motor and a low-profile design. It says the fan is UL507 compliant, ETL listed for indoor or outdoor use, and rated for residential and commercial use. Its dimensions table gives the XP151 and XP201 as 8.5 by 9.5 by 4.5 inches and the XR261 as 8.5 by 9.5 by 6 inches.

ENERGY STAR certifies some in-line fans and publishes each certified model's tested airflow and efficacy, in cubic feet per minute per watt. Two radon fans appear in its list of certified ventilating fans: Fantech's Rn 1 and RadonAway's RP140C. These are results from the program's own certification records, not the makers' brochures, and they are measured at the program's test conditions, so they do not match the maximum figures in the tables above.

Certification is a fact about energy use at a test point, not about how well a fan reduces radon in a given house. Many radon fans are not in the program at all, which says nothing either way about them.

The EPA's construction guide says the most commonly used radon fans are centrifugal in-line fans, and that the fan and every positively pressurized part of the vent pipe belong outside the building's habitable space, so a leak cannot push radon into the home. Fantech's manual recommends installation by a trained, licensed, certified mitigation professional and says radon fans are to be installed vertically only.

1. 1Step 1 of 5:

   Outside the living space

   The EPA says a fan cannot be inside the living space or in the crawlspace beneath the home; fans are most often in attics or garages, unless there is living space above the garage.

2. 2Step 2 of 5:

   In a vertical pipe run

   The EPA's guide says to install the fan in a vertical run of the vent pipe and that fans need a 30-inch vertical run of pipe.

3. 3Step 3 of 5:

   On an unswitched supply

   The EPA's guide says fans need an unswitched electrical junction box, so the fan cannot be turned off by accident.

4. 4Step 4 of 5:

   Running all the time

   The EPA says the fan should never be turned off; it must run continuously for the system to work.

5. 5Step 5 of 5:

   Tested once it runs

   Fantech's manual says checking radon levels after installation is required, and the EPA suggests retesting at least every two years.

On lifespan, the EPA says fans may last five years or more and that manufacturer warranties tend not to exceed five years, which matches the five-year warranties both makers here state. Systems that use fans are more effective at reducing radon, the EPA adds, but slightly increase the electric bill, which is where the power figures above come in.

For a new system, the fan is part of a design a mitigator makes after measuring how easily air moves under the slab; find one in radon mitigation professionals. For a replacement, the installed fan's model and the system's pressure gauge reading are the starting point, and the makers' tables above show how each fan's figures compare with what it replaces. How the whole system works is explained in how a radon fan works and on radon mitigation fans.