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Illinois: homes, climate zones and who licenses the work

Illinois has 5.5 million housing units. 63.5% were built before 1980, and the median year built is 1971. 67.1% of occupied homes are lived in by their owners.

How old the homes are

Illinois housing units, by year built

Layers drawn to scale

Illinois housing units by year built 63.5% of Illinois housing units were built before 1980 and 36.5% in 1980 or later. 2020 or later: 0.7%; 2010–2019: 5.0%; 2000–2009: 11.2%; 1990–1999: 10.5%; 1980–1989: 9.2%; 1970–1979: 14.2%; 1960–1969: 11.5%; 1950–1959: 11.9%; 1940–1949: 5.6%; 1939 or earlier: 20.2%. Before 1980 63.5% 1980 or later 36.5% 2020 or later 0.7% 2010–2019 5.0% 2000–2009 11.2% 1990–1999 10.5% 1980–1989 9.2% 1970–1979 14.2% 1960–1969 11.5% 1950–1959 11.9% 1940–1949 5.6% 1939 or earlier 20.2%
Source: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, tables B25034, B25035 and B25003; heating fuel below from B25040.

Age changes what applies to a house. In general, anyone paid to do work that disturbs painted surfaces in a home built before 1978 must be certified in lead-safe work practices under the EPA's Renovation, Repair and Painting Rule, which the EPA administers directly in Illinois.

How homes are heated

How homes in Illinois are heated

Main heating fuel, share of 5.0 million occupied homes

  • Utility gas 75.3%
  • Electricity 18.6%
  • Propane or other tank gas 4.2%
  • No fuel used 0.8%
  • Other fuel 0.5%
  • Wood 0.3%
  • Fuel oil or kerosene 0.1%
  • Solar energy 0.1%
  • Coal or coke <0.1%
Source: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, table B25040 (occupied housing units).

Climate and building zones

The 2021 International Energy Conservation Code assigns every county a climate zone from 1 to 8 and a moisture regime: A for moist, B for dry, C for marine. Zones 7 and 8 have no letter. Here is how Illinois's residents divide among them, by the county they live in.

IECC 2021 zoneShare of residentsCounties
5A88.9%58
4A11.1%44

ENERGY STAR rates windows, doors and skylights for four climate zones of its own. Illinois spans 2: Northern (88.9% of residents), North-Central (11.1% of residents).

By NOAA's 1991–2020 climate normals, counties here average 114 days a year with a low of 32°F or colder, weighted by where people live. The range runs from 80 days in the mildest county to 156 in the coldest.

Flood risk and flood insurance

0.5% of residential structures in Illinois carry a National Flood Insurance Program policy: 21,080 policies, in FEMA's count as of August 3, 2026.

In FEMA's National Risk Index, 7 of 102 counties rate high or very high for riverine flooding.

Fire ants and termites

No county in Illinois is inside the federal imported fire ant quarantine.

Who licenses the work in Illinois

Before anyone starts work, check the license with the agency below. Where the state does not license a trade, cities and counties may; ask the one where the house is.

Checked 2026-09-29. Licensing rules change; the agency's own page is the authority.

Sources

  1. U.S. Census Bureau American Community Survey 2020–2024 5-year estimates, tables B25034, B25035, B25040 and B25003 data.census.gov
  2. Pacific Northwest National Laboratory Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates basc.pnnl.gov
  3. U.S. Department of Energy Prototype Building Models (climate zones 1–8 and moisture regimes A, B, C) energycodes.gov
  4. ENERGY STAR Climate zones by county for windows, doors and skylights energystar.gov
  5. NOAA National Centers for Environmental Information U.S. Climate Normals 1991–2020, annual and seasonal ncei.noaa.gov
  6. Federal Emergency Management Agency OpenFEMA NFIP Residential Penetration Rates (as of 2026-08-03) fema.gov
  7. Federal Emergency Management Agency National Risk Index, county ratings fema.gov
  8. USDA Animal and Plant Health Inspection Service Imported fire ant quarantine map aphis.usda.gov
  9. Electronic Code of Federal Regulations 7 CFR part 301, subpart P, Imported Fire Ant ecfr.gov
  10. Illinois Department of Public Health, Structural Pest Control Program dph.illinois.gov dph.illinois.gov
  11. illinoisattorneygeneral.gov illinoisattorneygeneral.gov illinoisattorneygeneral.gov
  12. Illinois Department of Public Health dph.illinois.gov dph.illinois.gov
  13. Illinois Department of Public Health dph.illinois.gov dph.illinois.gov
  14. epa.gov epa.gov epa.gov