Walk through a model home at Riverview Preserve or a spec build in Martin Farms and the sales rep will talk your ear off about quartz upgrades, the transferable structural warranty, and how many months until the concrete cures enough to pour the driveway. What nobody walks you through is the radon system that's already been engineered into the slab before you ever toured the lot. It's not an upgrade you choose. It's code. And in Wright County, the version the code requires might not be the version your house actually needs.
That gap between what's required and what's sufficient is the thing worth understanding before you sign, not after you move in.
What "Radon-Resistant Construction" Actually Requires
Since 2009, Minnesota's building code has required every new residential structure to include a passive radon control system. The Minnesota Department of Labor and Industry spells out exactly what that means: four inches of clean aggregate spread beneath the slab, a sealed foundation with all potential gas entry points caulked or foamed shut, and a three to four inch PVC vent pipe that runs from below the foundation straight up through the roof. Builders also rough in an electrical junction box in the attic near that pipe, so the system is ready to be "activated" later if needed.
That word, passive, is doing a lot of work. A passive system relies on natural upward airflow to carry soil gas out through the vent pipe. There's no fan. An active system adds one, mounted in an unconditioned space like the attic, along with a monitor to confirm it's running and an outlet to power it. Minnesota code requires the passive version in every new home. It does not require the fan.
That distinction rarely comes up during a design center appointment, because there's nothing to select. The passive system is already built. Whether it needs a fan is a separate question, and it's one the builder isn't required to answer for you unprompted.
The Number That Makes This a Wright County Question, Not a Generic One
Radon risk isn't uniform across Minnesota, and Wright County's own numbers are the reason this matters here specifically. Based on test results submitted through Air Chek, the average indoor radon level recorded in Wright County sits at 3.9 pCi/L. The EPA's action level, the point at which the state recommends mitigation, is 4.0 pCi/L.
That average sits close enough to the line that it deserves a second look rather than a shrug. It's also worth remembering what that average actually represents: it's built from homes where someone chose to test, which likely skews toward households that had some reason for concern in the first place. Whether that pulls the true county-wide average up or down, the point stands either way. A county average this close to the action level means a meaningful share of individual homes are landing above it, and a passive-only system offers no guarantee that yours won't be one of them.
What Your Test Result Actually Means
The Minnesota Department of Health has a specific decision tree for what to do once you have a number in hand.
| Test result | Recommended action |
|---|---|
| 0 to 1.9 pCi/L | Retest every 2 to 5 years |
| 2.0 to 3.9 pCi/L | Consider installing a mitigation system |
| 4.0 pCi/L or higher | Mitigation is recommended |
Given that Wright County's average sits inside that middle band, a lot of buyers here are going to land in "consider it" territory rather than a clean pass. That's a different position than most new-construction marketing implies.
The Cheap Question and the Expensive One
Here's the part that actually changes how you should approach a new build. Upgrading a passive system to active means adding an in-line fan, and the state's own cost data makes clear it isn't the expense that should stop anyone. The Department of Health estimates a radon reduction system costs a little more than $14 a year to run, compared to roughly $78 a year for a home computer.
The real cost difference isn't the fan itself. It's timing. While the house is still framed, that junction box is sitting in an open attic and the vent stack is exposed. Adding the fan at that stage is a straightforward electrical and mechanical task. Once drywall, insulation, and a finished basement go in, the same job means cutting into finished space to reach the same pipe. The state health department no longer keeps an official list of builders who include active systems by default, so this isn't something you can assume from a builder's reputation. You have to ask, and the best time to ask is before drywall, not after your first winter in the house.
Bringing This Up at Riverview Preserve, Martin Farms, or Anywhere Else in Town
Riverview Preserve is currently being built out by both M/I Homes and Hanson Builders, and Martin Farms has been one of the more established new-construction pockets in St. Michael for a while now. Regardless of which subdivision or builder you're working with, the conversation is the same one: ask whether the passive system already includes the attic-mounted fan, or whether it's structured so a fan can be added easily before the walls close up. If the answer is "we can add that," get it in writing as part of your purchase agreement, not as a verbal promise from your sales rep. A pre-drywall walkthrough, if your builder offers one, is the natural point to raise it, since the attic and stud bays are still open for exactly this kind of change.
The Disclosure Question New Construction Buyers Tend to Skip
Minnesota's Radon Awareness Act requires a seller to disclose, in writing, any knowledge they have of radon concentrations in a dwelling before a purchase agreement is signed. That includes whether any test has been performed, the most current test records, and a description of any mitigation or remediation already in place. Buyers of resale homes are used to seeing this disclosure. Buyers signing directly with a builder sometimes assume it doesn't apply to them, since there's no "history" on a brand-new house. But a builder selling a completed spec home is a seller too, and the same disclosure obligations follow the transaction.
It's also worth knowing that anyone who performs a radon test or installs a mitigation system in a home they don't own must be licensed by the Minnesota Department of Health under the state's Radon Licensing Act. A general contractor certification isn't a substitute. If a builder tells you the home has already been tested, ask who performed it and whether they can produce that license.
Testing on a New-Build Timeline
Resale buyers usually test during their inspection contingency window. New construction doesn't come with that same built-in checkpoint, so the test tends to happen later, often after the first heating season once the house has settled and been lived in under normal closed-house conditions. A short-term test runs a minimum of 48 hours, and the device goes in the lowest livable level of the home. In St. Michael, where basements are the norm rather than the exception, that's where the test needs to sit.
If your result comes back in that 2.0 to 3.9 pCi/L range, that's the point where having a fan already roughed in during construction starts to pay off. Instead of a retrofit project, it's an activation.
A Few Questions Worth Settling Before You Sign
Does a brand new home actually need a radon test if it already has the required system? Yes. The passive system reduces risk, it doesn't eliminate the need to test. State health guidance treats new construction the same as any other home purchase on this point.
Can I ask the builder to add the fan before the house is finished? That's the ask worth making, and the earlier in the build schedule you make it, the simpler it is for the builder to say yes without extra cost or disruption.
Is a builder legally required to tell me if a home has been tested? Under the Radon Awareness Act, any known radon information has to be disclosed in writing before you sign a purchase agreement, whether you're buying resale or new construction from a builder.
What if my result lands between 2.0 and 3.9 pCi/L? The state's guidance is to consider installing a mitigation system at that range. If the fan and monitor were already roughed in during framing, that decision becomes a quick activation rather than a construction project.
New construction in St. Michael comes with a lot of things already decided for you, and the radon system is one of them. Knowing which version you're getting, and when it's still cheap to change, is the kind of detail that's easy to miss between choosing cabinet finishes and picking a closing date. If you're under contract or about to be at Riverview Preserve, Martin Farms, or anywhere else new construction is going up around town, Stephanie Houghton can walk through exactly what to ask your builder before drywall goes up. Let's Connect.
