Properly installed foam is inert, doesn't settle, and doesn't degrade. It lasts the lifetime of the building. Workmanship warranty terms are set by your lead technician; the foam material itself outlives the home regardless.
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The longevity claim is strong and supported by field data. Spray polyurethane foam installations from the 1980s and 1990s are still performing in field testing (Building Research Establishment UK, NIST USA studies have looked at 30-50 year-old installations). The polymer chemistry produces a thermoset plastic that does not depolymerize at room temperature; the failure modes that affect other insulations (settling, sagging, compression, moisture damage, pest nesting) do not affect cured foam meaningfully. The two practical limits on lifespan: (1) UV exposure if the foam is somehow exposed to direct sunlight (shouldn't happen in proper installs), and (2) major building modifications that disturb the foam mechanically. Manufacturer material warranties are conservative: Demilec, Icynene, BASF all offer 25-year limited warranties on the foam material. Workmanship warranties from credentialed Cincinnati installers run 1-10 years depending on the contractor. Cincinnati 30-year track record: our Cincinnati installers report on installations from 1985-1995 that are still performing at original spec when inspected. The 25-50 year material-warranty windows are conservative; real-world performance commonly exceeds them. Workmanship-warranty length matters more for early-life issues (sealing miss, fan adjustment) than for material concerns, since the foam itself rarely fails.