Foam itself does not feed mold. Closed-cell foam is impermeable to water, preventing the moisture that mold requires. Improperly applied foam can trap moisture; every install here is designed around the home's ventilation strategy.
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Mold requires three things: organic food source, moisture, and time. Closed-cell foam is non-organic and impermeable to liquid water and vapor (above 2-inch thickness). Open-cell foam is non-organic but vapor-permeable. Foam itself never feeds mold. The mold-related risks come from how foam interacts with the assembly. (1) If foam is sprayed over moldy or wet existing insulation, the moldy material remains under the foam; remediate first, foam after. (2) If foam encapsulates a moisture source (active leak, condensation prone surface), the trapped moisture can support mold growth on adjacent organic materials (wood framing, drywall paper). Moisture sources are identified and remediated before spraying. (3) In tightly-foamed homes without mechanical ventilation, indoor humidity can rise enough to support mold growth on cool surfaces (window sills, exterior walls in cold weather). Solution: install an HRV or ERV. Cincinnati moisture-source remediation note: any foam project in a basement, crawl space, or rim-joist application requires identifying and remediating moisture sources before spraying. Common Cincinnati moisture sources include leaking foundation walls, failed gutter drainage routing water toward the foundation, plumbing leaks behind walls, and condensation on cold surfaces in shoulder-season transitions. Thermal imaging during the on-site assessment identifies these.