Radon Mitigation
An installed system is a claim; a retest is the evidence. We include one with every system we build, because a job that was never verified looks exactly like one that failed — a white pipe with a fan on it. The retest also completes the paperwork a future buyer will ask for under Minnesota's disclosure law: the reading before and the reading after. We also retest systems we did not install, including the passive pipes that have been sitting in post-2009 houses without anyone checking whether they do anything.
A working radon system and a failed one look the same from the driveway — a white pipe and a fan. The only thing that tells them apart is a measurement taken while the system runs. That is why every system we install includes a retest, and why we will retest systems other companies built. It is also the second half of the paperwork a buyer will expect under Minnesota's disclosure law: the reading before and the reading after.
Not immediately. The fan needs to run for at least 24 hours so the pressure field under the slab settles, and the test is run under the same closed-house conditions as the original so the two numbers can be compared honestly. A retest done in July against a January baseline is not a fair comparison either way, and we will say so.
Every Twin Cities house built since June 2009 should have a passive radon pipe from the slab to the attic, installed to code and never measured. Many owners assume it is a working system. It may be. It may also read well above the action level, because natural draft depends on the weather and the house. A test is the only way to know, and if the number is high, adding a fan to the existing pipe is usually a small job.
Houses change, and systems that once worked stop working. Finishing the basement adds framing and flooring over the slab. A new high-efficiency furnace or water heater changes how the house pulls air. New windows tighten the house. An addition can be built over the only suction point. Any of these is a reason to retest, and so is a gauge on the pipe that shows level columns.
Then the job is not finished. The usual fixes are another suction point, more sealing around the sump or drains, or a fan better matched to the fill under the slab. On a system we built, that is ours to put right, and the design notes from the original install usually point straight at the cause.
How long does it take? The same 48 hours, run at least 24 hours after the fan has been switched on so the sub-slab pressure field has settled.
These usually come up in the same conversation:
The standard fix for a Twin Cities basement or slab: suction under the floor, the gaps sealed, a fan outside the living space and a discharge above the roof — built for a Minnesota winter.
Learn More →A continuous monitor in the lowest lived-in level for at least 48 hours, logging every hour — a curve you can read, not one number that might be a fluke.
Learn More →Dead fans, iced discharges, passive pipes that never worked. We test first, then fix what the reading says is wrong.
Learn More →Free · No Obligation
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