Spray polyurethane foam (SPF) is a two-component liquid that mixes at the spray gun, expanding 30-100x to fill cavities completely. It hardens into a rigid (closed-cell) or flexible (open-cell) insulating mass.
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The two components are polyol resin (Side B, contains blowing agent and amine catalyst) and isocyanate (Side A, MDI). They mix at the spray gun, react chemically (exothermic polymerization), and expand to fill the application area within seconds. Cure to walking-firm in 30-60 seconds, full chemical cure in 24 hours. Application requires PPE (Tyvek suit, full-face respirator with organic-vapor cartridge) and proper spray-zone ventilation. Truck-mounted equipment ensures consistent mix ratios; on-site mix monitoring catches off-ratio events that would result in soft, sticky, or odoriferous foam. Our Cincinnati installers use Graco or PMC reactor units with calibrated proportioner pumps and continuous-monitoring sensors. The two product families used most often locally: Demilec (open and closed-cell), Icynene (open-cell focus), BASF Walltite (closed-cell). All three meet ICC-ES code requirements for residential application. Cincinnati-area product-selection logic: the choice among Demilec, Icynene, BASF, and other approved foam products comes down to specific performance requirements, contractor experience, and available product supply. Most Greater Cincinnati installers carry 2-3 product lines for varied applications. Homeowners who care about specific certifications (GREENGUARD, BREEAM, etc.) should ask at quote time; most products meet the major certifications.