The heating season, roughly October through March, when houses stay closed and warm air rising indoors draws harder on the soil. A result from those months is a stronger basis for a decision than a summer short-term test.
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Central Ohio sits in IECC climate zone 5A, a colder zone than Cincinnati's 4A, so the closed-house season runs long. Warm air rising through a heated house leaves the lowest level at slightly lower pressure than the soil, and that difference pulls soil gas inside; in mild weather with windows open the effect fades. Ohio's protocol already requires closed-building conditions for short tests, which narrows the gap, but it cannot recreate January in July. Two practical cautions: do not run a short test during a severe storm or sustained winds of 30 mph or more, and if you travel mid-test, keep the heat running normally. A long-term test of more than 90 days captures the whole swing. See the heating-season testing plan.