HRVs help by introducing fresh outside air, but typically not enough to reach EPA action level on their own. They work as a supplement to active depressurization, not a replacement.
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HRVs and ERVs (energy recovery ventilators) introduce fresh outside air at a controlled rate while exhausting equivalent stale air, recovering heat (HRV) or heat plus moisture (ERV) in the process. In Cincinnati climate they are increasingly common in tight new construction and after spray-foam retrofits that drop ACH50 below 5. Effect on radon: dilution. A 100 CFM HRV running continuously in a tight 2,000 sqft home introduces roughly 0.3 air changes per hour of fresh air, which dilutes indoor radon by an equivalent factor. That is meaningful (a home reading 4.5 pCi/L might drop to 2.5-3.0 pCi/L with HRV alone) but usually insufficient to reach the EPA action level. Active sub-slab depressurization addresses radon at the entry point and is more effective per dollar spent. HRVs and active mitigation together are the gold standard for tight, conditioned, low-radon homes. Cincinnati climate compatibility: ERVs (energy recovery ventilators) generally outperform HRVs in Cincinnati Climate Zone 4A because the summer humidity recovery feature substantially reduces latent cooling load on the air conditioner. Most Cincinnati-area whole-home foam packages spec ERVs over HRVs. Cost differential is modest ($200-$400 for the ERV upgrade) and the comfort and bill-savings differential is consistent.