State facts
Delaware: homes, climate zones and who licenses the work
Delaware has 464,000 housing units. 41.9% were built before 1980, and the median year built is 1987. 73% of occupied homes are lived in by their owners.
How old the homes are
Delaware housing units, by year built
Layers drawn to scale
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 Delaware Division of Public Health, Healthy Homes and Lead Poisoning Prevention Program administers in Delaware.
How homes are heated
How homes in Delaware are heated
Main heating fuel, share of about 402,000 occupied homes
- Utility gas 41.9%
- Electricity 37.9%
- Propane or other tank gas 9.2%
- Fuel oil or kerosene 8.8%
- Wood 0.6%
- Other fuel 0.6%
- No fuel used 0.6%
- Solar energy 0.2%
- Coal or coke 0.1%
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 Delaware's residents divide among them, by the county they live in.
| IECC 2021 zone | Share of residents | Counties |
|---|---|---|
| 4A | 100% | 3 |
ENERGY STAR rates windows, doors and skylights for four climate zones of its own. All of Delaware falls in the North-Central zone.
By NOAA's 1991–2020 climate normals, counties here average 87 days a year with a low of 32°F or colder, weighted by where people live. The range runs from 79 days in the mildest county to 92 in the coldest.
Flood risk and flood insurance
4.8% of residential structures in Delaware carry a National Flood Insurance Program policy: 17,547 policies, in FEMA's count as of August 3, 2026.
In FEMA's National Risk Index, 1 of 3 counties rates high or very high for riverine flooding; 2 of 3 counties rate high or very high for coastal flooding; 1 of 3 counties rates high or very high for hurricanes.
Fire ants and termites
No county in Delaware is inside the federal imported fire ant quarantine.
Who licenses the work in Delaware
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.
- Pest control A business that applies pesticides to other people's property for pay needs a Pesticide Business License, and its applicators must be certified commercial applicators in their categories, which include general pest control (7A), wood destroying pests (7B) and fumigation (7C). Agency: Delaware Department of Agriculture. Who to call about pest control.
- Heating and cooling HVACR services must be provided by, or under the supervision of, a state-licensed master HVACR or master restricted HVACR licensee. Agency: Delaware Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners. Look up a license. Who to call about heating and cooling.
- Window replacement and other home improvement Every contractor, resident or nonresident, that alters or repairs buildings in Delaware must register with and get a contractor business license from the Division of Revenue. Agency: Delaware Division of Revenue. Look up a license. Who to call about window replacement.
- Mold remediation We found no statewide license for this work in official sources. Cities and counties may license it; ask the one where the house is. Who to call about water damage and mold.
Checked 2026-09-29. Licensing rules change; the agency's own page is the authority.
Sources
- U.S. Census Bureau American Community Survey 2020–2024 5-year estimates, tables B25034, B25035, B25040 and B25003 data.census.gov
- Pacific Northwest National Laboratory Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates basc.pnnl.gov
- U.S. Department of Energy Prototype Building Models (climate zones 1–8 and moisture regimes A, B, C) energycodes.gov
- ENERGY STAR Climate zones by county for windows, doors and skylights energystar.gov
- NOAA National Centers for Environmental Information U.S. Climate Normals 1991–2020, annual and seasonal ncei.noaa.gov
- Federal Emergency Management Agency OpenFEMA NFIP Residential Penetration Rates (as of 2026-08-03) fema.gov
- Federal Emergency Management Agency National Risk Index, county ratings fema.gov
- USDA Animal and Plant Health Inspection Service Imported fire ant quarantine map aphis.usda.gov
- Electronic Code of Federal Regulations 7 CFR part 301, subpart P, Imported Fire Ant ecfr.gov
- Delaware Department of Agriculture agriculture.delaware.gov agriculture.delaware.gov
- Delaware Department of Agriculture agriculture.delaware.gov agriculture.delaware.gov
- Delaware Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners dpr.delaware.gov dpr.delaware.gov
- Delaware Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners delcode.delaware.gov delcode.delaware.gov
- Delaware Division of Revenue revenue.delaware.gov revenue.delaware.gov
- Delaware Division of Revenue delcode.delaware.gov delcode.delaware.gov
- Delaware Division of Public Health, Healthy Homes and Lead Poisoning Prevention Program epa.gov epa.gov
- Delaware Division of Public Health, Healthy Homes and Lead Poisoning Prevention Program firststeps.delaware.gov firststeps.delaware.gov