If your HVAC is in the attic: spray the roof deck (creates a conditioned attic). If HVAC is in conditioned space: spray the attic floor. The wrong choice can create moisture problems; the on-site estimate confirms which is right for your home.
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The decision rule is where the conditioned envelope ends. (1) HVAC equipment in the attic: spray the roof deck. This brings the attic inside the conditioned envelope. The HVAC equipment is no longer operating in 130°F summer heat and 20°F winter cold. Energy savings 30-45% on cooling load alone in many Columbus homes. Required: closed-cell foam in Columbus Zone 5A climate to maintain vapor performance. (2) HVAC equipment in conditioned space (basement or interior closet): spray the attic floor. The attic stays vented and unconditioned; the floor air-seals and insulates the boundary. Open-cell foam works fine on attic floors with proper soffit ventilation; reach the Zone 5A R-49 to R-60 target at 13 to 17 inches. (3) Mixed configuration (HVAC partly in attic, partly elsewhere): Columbus-area installer evaluates and typically recommends roof-deck foam for the cleaner result. Wrong choice consequences: floor-foam with HVAC in attic leaves equipment exposed to extreme temps, wasting most of the savings. Roof-deck foam without ventilation strategy can trap moisture in unvented assemblies. Columbus pre-existing-HVAC consideration: many older Clintonville, Worthington, and Upper Arlington homes have HVAC equipment in the attic from 1990s-2000s upgrades that simplified ductwork. Roof-deck foam in those homes typically delivers the highest energy savings because it brings the equipment into the conditioned envelope. Existing equipment gets identified and routed around during the on-site assessment.