Radon Mitigation Systems in Minneapolis, MN

How Sub-Slab Suction Works

The system is simple in principle. A hole is cored through the basement floor and a small pit is dug out of the fill beneath it. A sealed pipe runs from that pit to a fan, and the fan holds the space under the concrete at a slightly lower pressure than the room above. Soil gas follows the pressure: instead of rising through the wall joint, the sump basket or a crack, it is drawn into the pipe and discharged above the roof edge where it disperses. How far that suction reaches depends on what is under the slab, which is why we test the sub-slab material before settling on a design.

Designing for Twenty Below

The air a radon system pulls from under a slab is warm and damp. On a January night that moisture condenses in the pipe, and anywhere it can collect it can freeze — at an exterior fan, in a sagging horizontal run, or as a cap of ice on the discharge. Minnesota systems are built around that: pipe sloped so condensate drains back down to the slab, fans placed where they stay serviceable, and wherever the house allows, a route through the attached garage or an interior closet to the attic rather than up an exposed outside wall. An interior route costs more and keeps working in February.

The Sealing That Makes It Efficient

Twin Cities basements come with built-in shortcuts to the soil. Sump baskets sit over perimeter drain tile. Older houses have floor drains whose traps dry out. Block walls meet the floor with an open joint. Every one of those lets the fan pull basement air instead of soil gas, which weakens the system and — in a state where you heat the house for half the year — sends paid-for warm air out of the roof. Sealing them is part of the install, not an upsell.

Houses That Already Have a Pipe

Every new Minnesota home since June 2009 has been built with a passive radon system: gravel or a venting mat under the slab, a sealed pipe running up through the house, and usually a labelled pipe in the attic with space to add a fan. Passive systems rely on natural draft and are rarely tested. When one reads high, activating it — adding a fan in the attic and a gauge on the pipe — is a much smaller job than building a system from nothing, and it is the first thing we look for in any house from the last fifteen years.

Proving It Worked

Every system we install gets a U-tube gauge so a dead fan is visible at a glance, and every system gets a retest once it has run long enough for the pressure under the slab to settle. The before and after readings go to you together. Under Minnesota's disclosure law those two documents are exactly what a future buyer will ask to see.

How long does it take? Most single-family systems go in inside a day. Complicated foundations — several slabs at different levels, an addition, a crawlspace tied in — can run to two.

Questions People Ask First