2018 IRC, Appendix Q only.
Tennessee’s statewide residential standard adopts the 2018 IRC and Appendix Q. Appendix F is not part of the statewide adoption; the 2018-edition rule became effective July 16, 2020.3
The county picture
A stronger local signal than the zone label.
The official planning label is EPA Zone 2, but a 2003 East Tennessee State University thesis measured 69 Unicoi County homes and found a mean of 4.03 ± 3.04 pCi/L—well above the EPA comparison mean of 1.96 ± 1.08 used in the study. The researcher concluded that the county should be re-categorized from moderate to high risk.6
Official risk profile
EPA Zone
2
Zone 2 is the moderate-potential category, associated with predicted average indoor screening levels of 2–4 pCi/L.7 It is a county-scale planning estimate, not a reading for an address.
The county’s own study changes the conversation.
ETSU thesis · August 2003
4.03 pCi/LMean long-term measurement across 69 Unicoi County homes, with a reported ±3.04 pCi/L spread.6
The study’s EPA comparison mean was 1.96 ± 1.08 pCi/L; its Radon Index Matrix analysis moved Unicoi County from moderate to high risk.6
69County homes in the ETSU study
2003Year the thesis was awarded
HighStudy’s recommended risk category
!State dashboard values withheld
The Tennessee Radon Testing dashboard covers 2022–2023, but no county-labeled Unicoi tooltip value could be read on two live loads.8
Its pre- and post-mitigation charts aggregate by Northeast Region, not Unicoi County. No dashboard average, median, maximum, count or percentage is presented here as county data.
Building codes
No dependable radon-ready requirement
A jurisdiction can adopt the IRC without adopting its optional radon appendix. The appendix list—not the code edition alone—decides whether those features are mandatory.
Jurisdiction
Radon status
What the record supports
Town of ErwinOptional
Erwin Municipal Code §12-501 adopts the 2018 IRC with appendices A, B, C, E, G, J, K, N, P and Q. Appendix F—Radon Control Methods—is absent. The record cites Ord. #689-17 from May 2017, amended by Ord. #725-21 in June 2021.116
Unincorporated Unicoi CountyAppears opted out
Unicoi County is not on the current SFMO list of counties where a state residential permit is required. A 2011 MTAS table labels the county “OPT OUT,” but that status must be renewed after elections and needs local confirmation.45
Town of UnicoiAppendices open
Ord. #2021-295 from July 2021 adopted “the 2018 International Building Codes,” but the research did not establish the residential appendix list. No mandatory radon provision is claimed here.2
Ask for the feature—and verify it.
In Erwin, radon-resistant construction is optional. In the unincorporated county, the evidence points to no residential enforcement program at all. For the Town of Unicoi, confirm the current appendix list before relying on a builder’s code claim.124
Public rules & transactions
No special local radon regime was found
The reviewed sources showed no Unicoi County- or Erwin-specific requirement for public buildings, schools or residential transactions beyond Tennessee’s statewide framework.
Schools
Tennessee law encourages local education agencies to conduct indoor-air-quality programs that may include radon testing. The statute does not make testing mandatory.13
Home sales
Tennessee’s property-condition disclosure advises buyers to include a radon inspection contingency. No statewide radon-specific testing or repair mandate was found.14
Free test kits
The Tennessee Department of Environment and Conservation’s Radon Program offers free test kits to homeowners and recommends using certified professionals.15
How do I find a certified radon professional in Unicoi County?
Tennessee doesn't license radon testers or mitigators, so national certification is the best way to check qualifications. The Tennessee Radon Program points residents to two directories: search them by ZIP code and widen the radius if nothing is listed nearby.
We don't recommend or rank companies. Before you hire, check the certification number in the directory yourself and ask for a follow-up test after any system is installed. Questions to ask a radon professional.
Homebuyer guidance
In an older, resale-led market, testing is the backstop.
Unicoi County’s small new-construction pipeline and voluntary radon protections make a property-specific test more useful than assumptions based on age, price or ZIP code.
01
Test at the transaction
The county reported 8,825 housing units but only 28 building permits in 2025. Most home purchases are existing homes, where buyers should put the testing window in writing.1114
02
Do not equate new with radon-ready
Erwin’s adopted appendix list omits radon controls, the statewide code omits them, and the unincorporated county appears outside residential enforcement. Ask what was installed, then test after occupancy.134
03
Use the local study, not fear
The 69-home ETSU study is a strong reason to test, not a prediction for every house. A measured result is the only way to know a specific home’s level.6
Questions answered
Unicoi County radon FAQ
Short answers grounded in the local study, municipal code, state rules, dashboard review and certification directories.
Yes. The county is officially EPA Zone 2, but an ETSU study of 69 local homes found a 4.03 pCi/L mean and concluded Unicoi County should be reclassified from moderate to high risk. The zone and study are screening context, not a substitute for testing a home.
No. Erwin’s 2018 IRC adoption lists appendices A, B, C, E, G, J, K, N, P and Q. Appendix F—Radon Control Methods—is not included.
The county is absent from the current state residential-permit list, and older records identify it as opted out. That points to no residential code enforcement or mandatory radon appendix, but the opt-out must be renewed after elections and should be confirmed with county or state officials.
Unicoi County’s map tooltip could not be read on two live loads. The dashboard’s pre- and post-mitigation charts report Northeast Region aggregates, not county figures, so no county average, median, maximum, count or percentage is published here.
No radon-specific testing mandate was found. Tennessee’s disclosure form advises buyers to include a radon inspection contingency, and TDEC offers free test kits.
Source ledger
Read the record
Official records establish the code framework; the ETSU thesis supplies the county-specific study; dashboard and certification-directory findings are dated observations from October 16, 2026.
- Erwin Municipal Code, Title 12 — 2018 IRC, adopted appendices and ordinance history.
- Town of Unicoi Municipal Code — 2018 code adoption record.
- Tennessee Rule 0780-02-23 — state adoption of the 2018 IRC with Appendix Q.
- Tennessee SFMO permit jurisdiction list — counties where a state residential permit is required.
- MTAS residential inspection status table — 2011 record listing Unicoi County as opted out and Erwin/Unicoi as exempt.
- ETSU thesis: A Re-Evaluation of the US EPA Radon Risk Categorization for Unicoi County — 69-home study and reclassification finding.
- EPA Map of Radon Zones: Tennessee — EPA Zone 2 designation.
- Tennessee Radon Testing dashboard — 2022–2023 map and Northeast Region band charts.
- NRPP professional directory — Erwin and Johnson City area results reviewed October 16, 2026.
- NRSB Find a Professional — Erwin-area and statewide results reviewed October 16, 2026.
- Census QuickFacts: Unicoi County — population, housing, ownership, value and permit context.
- Census QuickFacts: Erwin town — 2025 population estimate.
- T.C.A. §49-2-121 — school indoor-air-quality programs may include radon testing.
- Tennessee Residential Property Condition Disclosure — radon inspection-contingency guidance.
- Tennessee Department of Environment and Conservation — Radon Program and free test kits.
- 2018 IRC Appendix F — Radon Control Methods.
- BWXT in Erwin — hero image source.