Passive radon pipes in new Powell and Marysville homes: 6 myths

You closed on a new house in Powell, Lewis Center, Marysville or Plain City, and a white PVC pipe rises out of the basement floor with a radon sticker on it and no fan anywhere in sight. The builder called it radon-resistant construction, the inspection went fine, and now you are wondering whether that pipe does anything at all. Here are six things new-home owners commonly believe about it, and what holds up.

Myth 1: a brand-new house does not need a radon test

Fact: EPA says every new home should be tested as soon as possible after the owners move in, radon-resistant features or not.

A fresh foundation does not change what lies under it. The ground under a brand-new cul-de-sac is the same ground that was there before the first footer went in, and EPA maps both Delaware and Union counties in Zone 1, its highest radon category. Construction methods change how easily soil gas gets into a house, not whether the soil makes it.

EPA's guidance for new homes goes one step further: if the test comes back at 4 pCi/L or more, a vent fan can be added to the passive system already in place. That makes the test the hinge for every other myth below.

Myth 2: the pipe in the basement is a radon system

Fact: the pipe is one piece of a set of radon-resistant features, and by itself it is only a path for soil gas to follow.

EPA describes the full package for new construction:

• A gas-permeable layer under the slab, often about 4 inches of clean gravel, so soil gas can move freely beneath the floor.
• Plastic sheeting laid over that layer, or sealed sheeting over the ground in a crawlspace.
• Sealing and caulking of openings in the below-grade foundation.
• A 3- or 4-inch PVC vent pipe running from the gravel layer up through the house and out the roof.
• An electrical junction box in the attic for a future fan, plus one in the living space for a warning device.

Recognized approaches include IRC Appendix F, ASTM E1465-08 and the ANSI/AARST rough-in standard for new homes. Many builders install some version of this package, but it is the builder's choice, so do not assume your house got every piece. Without a fan the arrangement is passive: it relies on the natural upward draft in the pipe to carry gas out. Check the attic for that junction box; if it is there, the house was set up for the next step.

Myth 3: a passive pipe works about as well as a fan

Fact: EPA puts passive sub-slab suction at a 30 to 70 percent radon reduction, against 50 to 99 percent for active sub-slab suction with a fan.

EPA adds that passive systems may do better in cold climates, and Delaware and Franklin counties fall in IECC climate zone 5A, classed as cold. A winter draft helps the stack pull. It does not turn a 30 to 70 percent range into a promise, and nothing about the pipe tells you where your house lands inside that range. Only the test from the first myth can.

Myth 4: a pipe that goes into the attic is venting the gas

Fact: a pipe that stops in the attic is not a working system.

Soil gas has to leave the house above the roof. A vent that was roughed in only as far as the attic, capped for a future fan or left open under the roof deck, is not exhausting anything to the outdoors, and an open end can release soil gas into the attic itself. Take a flashlight up the hatch and follow the pipe; it should continue through the roof.

The route matters for activation too. Once a fan goes on, the Ohio Radon Mitigation Standards set the exhaust above the highest eave and as close to the ridge as possible, at least 12 inches above the roof surface and at least 10 feet off the ground, with at least 10 feet of clearance from any window, door or opening that sits less than 2 feet below it. A pipe that ends near a bedroom window may need rerouting before a fan goes on.

Myth 5: no license was needed to build it, so none is needed to add the fan

Fact: Ohio law exempts radon-resistant techniques used during new construction from licensing, but adding a fan afterward is mitigation work.

Under ORC 3723.02, a business that performs radon mitigation needs an Ohio mitigation contractor license, and on-site supervision of the work needs a licensed mitigation specialist. The law does let owners mitigate their own buildings. Either way, activation turns a passive stack into an active system, and a licensed activation has to meet the Ohio standard, which doubles as the right checklist for a homeowner doing the job:

• The fan goes in the attic, in a garage that is not beneath living space, or outdoors. Never in the basement, a crawlspace, or conditioned space.
• It hangs in a vertical run, is a model its maker sells for radon use, and connects to the pipe with removable couplings.
• The exhaust follows the roof and clearance rules above, with no rain cap.
• A monitor shows the fan is running or warns when it quits, and a manometer gets marked with the start-up reading.
• Labels identify the system on exposed pipe, at the fan and on the breaker.

Our FAQ on a passive radon pipe with no fan walks through how to tell whether yours is ready for one.

Myth 6: activating the pipe costs as much as a whole new system

Fact: adding a fan to an existing passive pipe typically runs $700 to $1,200 here, while a complete [active sub-slab system](/services/radon-mitigation-systems) runs $1,200 to $2,400.

The gravel layer, sheeting and pipe are already in the house, so the work centers on the fan, the wiring, the roof exit and the monitor. Ohio's rules then set a window for the post-mitigation test that opens 24 hours after the fan starts and closes at 30 days, so you know the activation did its job rather than assuming it did. For more on radon and new builds in general, see our new construction FAQ.

Your next step: test the lowest lived-in level of your new home this heating season. If it reads 4 pCi/L or higher, or you would rather have the fan running regardless, call or text us about activation in Powell, Marysville or anywhere across Delaware and Union counties.