Radon Mitigation Cost in Montana (2026)

Radon in Montana: One of the Nation's Highest-Risk States

Montana is a serious radon state. The combination of uranium-bearing granite across the Rocky Mountain front, historic mining activity (especially in Butte and the surrounding region), and well-sealed homes built for cold winters creates conditions for some of the highest residential radon readings in the US.

The Montana Department of Environmental Quality estimates that more than 60% of tested Montana homes exceed the EPA action level of 4.0 pCi/L. Cities with particularly high rates include:

• Butte: Average tested levels among the highest in the country, driven by mining history and granite geology
• Helena: Consistently high — granite-rich geology throughout the valley
• Missoula: Elevated levels despite the valley location; surrounding geology and building stock drive risk
• Great Falls: Moderate-high; prairie geology with some elevated pockets
• Billings: Zone 1–2; test before assuming safe

Cost by Foundation Type

Basement: $1,000–$2,200

Montana's cold climate means most homes have basements — often unfinished or lightly finished. These are generally straightforward to mitigate.

• Unfinished basement: $1,000–$1,600
• Finished basement: $1,400–$2,200

Slab-on-Grade: $950–$1,800

Found in newer construction in Billings, Bozeman, and suburban Missoula. Typically the least expensive.

Crawl Space: $2,500–$5,500

Older Montana homes, particularly in rural areas, often have crawl spaces. Rocky terrain and cold climate can complicate access and vapor barrier installation.

Montana-Specific Cost Factors

High radon levels: Montana homes with readings above 20 pCi/L — not uncommon in Butte and Helena — often require premium fans or multiple suction points. Add $400–$900 over base pricing.

Rural contractor shortage: Montana is geographically vast with a small population. In rural areas — everything outside Billings, Missoula, Great Falls, Helena, and Bozeman — certified contractors may be scarce. Expect possible travel fees and longer wait times.

Cold climate construction: Montana homes are tightly built for winter efficiency, which tends to raise indoor radon levels. The flip side: depressurization systems work very effectively in well-sealed Montana homes.

Mining legacy: If your home is in or near a historic mining area, ask your contractor about potential additional sources beyond typical soil-gas radon.

Montana Resources

• Montana DEQ Radon Program: deq.mt.gov (search "radon")
• Verify NRPP: radonproficiency.org
• Verify NRSB: nrsb.org

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