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Washington: homes, climate zones and who licenses the work

Washington has 3.3 million housing units. 43.4% were built before 1980, and the median year built is 1985. 63.8% of occupied homes are lived in by their owners.

How old the homes are

Washington housing units, by year built

Layers drawn to scale

Washington housing units by year built 43.4% of Washington housing units were built before 1980 and 56.6% in 1980 or later. 2020 or later: 2.3%; 2010–2019: 12.1%; 2000–2009: 15.1%; 1990–1999: 14.8%; 1980–1989: 12.4%; 1970–1979: 14.2%; 1960–1969: 8.7%; 1950–1959: 6.7%; 1940–1949: 4.2%; 1939 or earlier: 9.6%. Before 1980 43.4% 1980 or later 56.6% 2020 or later 2.3% 2010–2019 12.1% 2000–2009 15.1% 1990–1999 14.8% 1980–1989 12.4% 1970–1979 14.2% 1960–1969 8.7% 1950–1959 6.7% 1940–1949 4.2% 1939 or earlier 9.6%
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 Washington State Department of Commerce administers in Washington.

How homes are heated

How homes in Washington are heated

Main heating fuel, share of 3.1 million occupied homes

  • Electricity 58.6%
  • Utility gas 33.0%
  • Propane or other tank gas 3.0%
  • Wood 2.8%
  • Fuel oil or kerosene 1.3%
  • No fuel used 0.6%
  • Other fuel 0.4%
  • Solar energy 0.2%
  • 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 Washington's residents divide among them, by the county they live in.

IECC 2021 zoneShare of residentsCounties
4C72.2%14
5B21%18
5C5.9%4
6B0.9%3

ENERGY STAR rates windows, doors and skylights for four climate zones of its own. All of Washington falls in the Northern zone.

By NOAA's 1991–2020 climate normals, counties here average 72 days a year with a low of 32°F or colder, weighted by where people live. The range runs from 32 days in the mildest county to 190 in the coldest.

Flood risk and flood insurance

0.9% of residential structures in Washington carry a National Flood Insurance Program policy: 23,122 policies, in FEMA's count as of August 3, 2026.

In FEMA's National Risk Index, 3 of 39 counties rate high or very high for riverine flooding; 2 of 39 counties rate high or very high for coastal flooding.

Fire ants and termites

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

Who licenses the work in Washington

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. Washington State Department of Agriculture agr.wa.gov agr.wa.gov
  11. Washington State Department of Labor & Industries lni.wa.gov lni.wa.gov
  12. Washington State Department of Labor & Industries app.leg.wa.gov app.leg.wa.gov
  13. Washington State Department of Commerce epa.gov epa.gov
  14. Washington State Department of Commerce commerce.wa.gov commerce.wa.gov