Radon-Resistant New Construction in Minnesota

Every new home built in Minnesota carries a piece of radon infrastructure most owners have never been told about. The state building code has required passive radon control systems in new residential construction for homes built after June 1, 2009. This guide covers what the rule includes, what the builder installed, why those homes still need testing, and the short path to fixing one that tests high.

The rule: Minnesota Rules 1303.2400 to 1303.2403

Minnesota Rules 1303.2400, the Radon Control Methods section of the State Building Code, sets minimum requirements for passive radon control in all new residential structures. Its scope is broad by design: it applies to designs with basement slabs in contact with the earth, crawl spaces inside the conditioned space, wood foundation floors on or above the earth, slab-on-grade construction, attached or tuck-under garages that are not fully sealed off, and any configuration that lets soil gas reach the dwelling. The Department of Labor and Industry, which administers the building code, summarizes the system in its radon control systems fact sheet.

What the builder installed

A gas-permeable layer or soil-gas collection point beneath the slab, so suction can spread under the foundation
A soil-gas membrane, with the foundation openings, joints, and penetrations sealed
A sealed vent pipe running from below the slab up through the roof, relying on stack effect
An attic route with space for a fan and an electrical outlet nearby, so the system can be activated later

The result is a system with no moving parts: warmer air rising in the sealed pipe slowly draws soil gas from beneath the membrane and discharges it above the roof. If a fan is later added, the rule treats it as an active radon control system, which brings requirements including a device that monitors whether the fan is working.

The gap between code-built and low-radon

Stack effect is a gentle force, and Minnesota soil delivers a steady supply of radon; the Minnesota Department of Health reports 2 in 5 tested homes statewide at levels posing a significant health risk. So the MDH guidance on radon-resistant new construction is blunt: test the home anyway. A passive house that tests low is done. A passive house that tests high is one fan away from done, which is a far better position than a pre-2009 home starting from scratch, and one reason activation jobs tend to land at the low end of the state's cost range, covered in our Minnesota cost guide.

Checklist for buyers of post-2009 homes

Find the pipe: look for a labeled PVC run through closets or the garage into the attic, and the stub above the roof
Ask the builder or seller where the vent runs and whether a fan was ever added
Test the home as soon as you occupy it, in the lowest lived-in level
If the result is at or above 4 pCi/L, have a licensed mitigation professional activate the system with a fan and verify with a follow-up test

Remember that Minnesota's radon disclosure law applies to new and newer homes exactly as it does to old ones: sellers disclose known radon records in writing before the purchase agreement. Growth markets with deep post-2009 stock, like St. Cloud, Bloomington infill, and Moorhead, are where these checklists earn their keep, and where passive-to-active conversions are everyday work for licensed contractors.

Minnesota RRNC Questions

Does my Minnesota home built after 2009 have a radon system?

If it is a residential building permitted after June 1, 2009 with a basement, crawl space in the conditioned area, slab-on-grade, or similar soil-contact design, Minnesota Rules 1303.2400 to 1303.2402 required a passive radon control system at construction. Look for the labeled vent pipe, typically rising through closets or the garage into the attic.

Why does a code-built home still test high for radon?

Passive systems rely on natural stack effect in the vent pipe, which moves little air compared to a fan. The Minnesota Department of Health recommends testing every new home for exactly that reason: in a state where MDH reports 2 in 5 tested homes high, plenty of passive homes still come in above 4 pCi/L until the system is activated.

What does it take to activate a passive radon system?

A licensed mitigation professional installs an inline radon fan on the existing vent pipe, normally in the attic space the code reserved, adds a monitor that shows the fan is running, and verifies the result with a follow-up radon test. Activation uses the pipe, roof penetration, and outlet the builder already provided.

Is a fan ever required in Minnesota new construction?

The statewide rule requires the passive system; adding a fan converts it to an active system that must then meet the active-system requirements in Minnesota Rules 1303.2400 to 1303.2403, including the performance monitoring device. Whether to activate is driven by your test result and the EPA action level of 4 pCi/L, not by the construction code alone.