Central Ohio county insulation reference: code zone, soils, and housing
Central Ohio is one climate zone but not one kind of house. The seven counties around Columbus all sit in Climate Zone 5A in the Residential Code of Ohio, yet the insulation work that pays differs between a German Village brick house, a Delaware County subdivision, and a pole barn outside Plain City. This reference pairs each county with its code zone, the towns in our service area, the housing eras that dominate there, and the envelope problems that come up most.
Two regional facts apply almost everywhere. Much of the area sits on glacial till with slow-draining soils such as the somewhat poorly drained Blount series, whose perched seasonal water table typically sits between 6 inches and 2 feet down in normal years, and the very poorly drained Pewamo series in low, flat spots. That matters for basements and crawl spaces. And the Ohio code design table credits Columbus with 5,660 heating degree days a year, so winter air leakage drives most of the savings.
| County | Code zone and service-area towns | Housing, and what usually pays first |
|---|---|---|
| Franklin | Zone 5A. Columbus, Clintonville, Upper Arlington, Grandview Heights, Bexley, Worthington, Whitehall, Hilliard, Gahanna, Grove City, and parts of Dublin, Westerville, New Albany, Reynoldsburg, and Canal Winchester | Pre-war brick and frame in German Village, Victorian Village, Olde Towne East, and Clintonville; period revival houses in Upper Arlington and Bexley; postwar ranches in Whitehall and Reynoldsburg. Rim joists and attic floor sealing first, wall fill in frame houses, and a moisture review before touching solid brick. |
| Delaware | Zone 5A. Powell, Lewis Center, Sunbury, Galena, the city of Delaware, and parts of Dublin and Westerville | Large 1990s to 2020s subdivisions with attic air handlers and bonus rooms over garages, a historic core in the city of Delaware, and rural acreage with pole barns. Roof deck foam where ducts sit in the attic, bonus room floors and knee walls, and steel building condensation. |
| Licking | Zone 5A. Pataskala, Granville, Johnstown, and parts of New Albany and Reynoldsburg | New construction around the Intel project in western Licking County, 19th-century village houses in Granville, and farms with outbuildings. Foam before drywall in new builds, careful work in historic village homes, and closed-cell in pole barns. |
| Fairfield | Zone 5A. Pickerington, Lancaster, and parts of Canal Winchester and Reynoldsburg | Subdivisions from the 1990s onward around Pickerington and older brick and frame housing in Lancaster. Rim joists and rooms over garages in newer homes; attic and wall work in pre-war Lancaster houses. |
| Union | Zone 5A. Marysville, part of Plain City, and part of Dublin | Growing subdivisions around Marysville, older in-town homes, and farm buildings. Crawl spaces and rim joists in newer homes, closed-cell in shops and pole barns. |
| Madison | Zone 5A. Part of Plain City | Mostly rural, with farm buildings and older farmhouses. Buildings certified for agricultural use are exempt from the state building code under Ohio Revised Code 3781.061; a barn converted to a heated shop or living space needs a thermal barrier over the foam. |
| Pickaway | Zone 5A | South of our listed service towns but in the same code zone, so the same Zone 5A values apply to homes and additions there. |
| Design climate, Columbus | 5,660 heating degree days; 5 degree winter design temperature | Residential Code of Ohio Table 301.2(1). The same table lists Cincinnati at 4,410 heating degree days, which is why winter air sealing pays back faster here. |
| Regional soils | Blount and Pewamo series common on the till plains | Somewhat poorly to very poorly drained, with perched or high seasonal water tables. Solve drainage before sealing a crawl space or insulating and finishing a basement. |
Town pages carry more local detail, for example Delaware, Marysville, Johnstown, and Lancaster. For the code values themselves, see the Zone 5A targets table. For what clay till means under a house, read crawl spaces on Central Ohio clay till.
Data sources
- Residential Code of Ohio, Chapter 11 Energy Efficiency, Table 1101.7 climate zones (OAC 4101:8-11-01)
- Residential Code of Ohio, Chapter 3, Table 301.2(1) design criteria (OAC 4101:8-3-01)
- USDA NRCS official soil series description: Blount
- USDA NRCS official soil series description: Pewamo
- Ohio Revised Code 3781.061, agricultural buildings
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