Radon mitigation cost vs. property value — the math before closing.

A typical residential mitigation system (sub-slab depressurization for a slab-on-grade or basement) costs $1,200–$2,500 installed. Zone 1 properties trend higher because the local contractor base is more experienced and demand supports the price. Crawlspace-only or unusual foundations can run $2,500–$5,000. The mitigation runs on a small fan (~90W continuous) — trivial operating cost.

Yes, but less than most buyers assume — and the effect is uneven. Paired-sale analyses in selected disclosure-state markets show measurable discounts on untreated homes with a documented high test result; no nationally representative estimate exists. With a mitigation system installed and a post-mitigation test showing <2 pCi/L, the discount disappears in most markets. Effect size tracks buyer awareness — stronger in states with a mandatory disclosure requirement (FL, IL, NJ, RI, others) than in states without one. Test your specific market before pricing this into an offer.

Zone 1 (red): predicted average indoor radon greater than 4 pCi/L — the EPA action level. Zone 2 (orange): predicted average 2–4 pCi/L. Zone 3 (yellow): predicted average less than 2 pCi/L. These are county-level predictions based on geology and past testing — individual homes vary widely. A Zone 3 house can test high; a Zone 1 house can test clean. The zone tells you what to expect on average, not what the specific house will read.

A short-term charcoal kit is $25–$50 including lab analysis, results in 48–96 hours after mailing. A long-term alpha-track test is $75–$200 and runs for 90 days — more accurate but obviously slower. A professional continuous monitor (used by inspectors) is $150–$300 for a two-day rental read. Buy the short-term kit; if it reads over 4 pCi/L, buy the long-term to confirm before spending on mitigation.

Almost always yes, if the property tests high. On a $300,000 property with a 3% Zone-1 resale discount ($9,000), a $2,000 mitigation system pays back 4.5x. The math flips only when: (a) the test comes back low so mitigation is unnecessary, (b) the buyer is not aware of radon at all (rare in disclosure states), or (c) the property will not resell for many years. Investors typically mitigate on the way in — the discount at buy plus the removal at sale is the trade.

In Zone 1 and Zone 2, testing before closing is standard practice — the seller typically pays for mitigation if the test reads over 4 pCi/L, and buyers write the contingency into the offer. In Zone 3, testing is optional but cheap. A $25 test that could save $2,000 in surprise costs is worth doing regardless of zone.

Accurate as a predictor for county-level averages, imperfect for any individual house. Local geology (uranium content in bedrock, soil permeability), house construction (basement vs. slab, HVAC pressure), and even weather patterns at time of testing all move the reading. Buildability queries the EPA zone data live at run time, so you always see the current designation — but the actual test on the property is the number that matters.

In some states — Florida, Illinois, New Jersey, Rhode Island, Kansas, Iowa, and others — sellers must disclose known radon test results or the property's radon zone. In non-disclosure states, most transactions still involve a radon contingency in the offer. The Buildability report timestamps the zone read so you have a defensible record either way.

Yes — all 50 states. EPA radon zone data covers every U.S. county, and Buildability queries it live for every parcel alongside the eight other factors that determine buildability.