What radon mitigation involves in a Wisconsin house

How a system works

Wisconsin DHS describes it simply. The contractor installs a pipe through the foundation, and a fan pulls radon from the soil under the house and vents it outside. The industry name is sub-slab depressurization.

Here’s what that looks like on the job. The installer drills through the basement slab and digs a small pit under it, called the suction point. PVC pipe runs from that pit up and out. An in-line fan on the pipe keeps a steady vacuum on the soil, so radon goes up the pipe instead of through the floor. The pipe discharges above the roof edge.

A U-shaped gauge on the pipe, called a manometer, shows the fan is pulling. If the liquid on both sides sits level, something’s wrong.

Activating a passive system

Some newer houses are built with a radon pipe already running from under the slab to the roof, but no fan. That’s a passive system. DHS notes a contractor can add a fan to turn it into an active one. If you have that pipe, test first. If the level is high, activating it is usually simpler than starting from scratch.

What goes into a good install

• Suction point location. A good installer checks how air moves under the slab before choosing a spot. Some houses need more than one.
• Fan outside the living space. The fan belongs in the attic, the garage, or on the exterior. Never in the basement or a lived-in room.
• Discharge above the roof. The pipe should vent above the roof edge and away from windows and doors.
• Sealing. The sump lid, open cracks, and the gap around the pipe at the slab all get sealed.
• Winter details. In a cold climate, an exterior pipe can collect condensation and frost. Ask how the installer handles freezing and drainage.
• Labeling. The pipe should be labeled as a radon system so nobody cuts into it later.

What affects the price

We don’t quote numbers, because prices change and every house is different. The cost depends on:

• How many suction points the house needs
• Whether the pipe runs inside, through the garage, or up the outside wall
• Crawlspaces, additions, or more than one foundation type
• Whether the fan needs a new electrical circuit
• How much sealing the foundation needs
• Whether a passive pipe is already in place

DHS recommends contacting at least three companies for estimates. Ask each one where the pipe and fan would go.

The retest

A system isn’t finished until it’s tested. Get a follow-up test after the fan has been running, and keep the result with your house papers. Test again every couple of years and after big changes like finishing the basement.

Start by finding a certified radon mitigator, or go back to the Wisconsin radon guide.