Sealing cracks and opening windows cost little but rarely get a house under 4 pCi/L; the EPA treats sealing as support for other methods, not a fix on its own. A fan-driven sub-slab system is the cost-effective route to a lasting result.
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The EPA's reduction table makes the point: active sub-slab suction cuts radon by 50 to 99 percent, passive suction without a fan by 30 to 70, and natural crawl-space ventilation by 0 to 50, while sealing is normally used only alongside another technique. Opening windows works only while they stay open, which is no plan for a zone 5A winter. The cheapest real fixes are in houses already set up for one: a builder's passive pipe that only needs a fan, $700 to $1,200 on the site's price list, or a slab home with an easy route to the attic. Most other homes start in the $1,200 to $2,400 range. Our pricing guide shows every tier.