The Chemistry of Closed-Cell Low-Expansion Foam: Rough Opening Sealing

## Polymer Chemistry in Window Rough Openings The rough opening gap between a new window frame and the 2x4 wall studs is the most vulnerable thermal interface in a home. Filling this 1/2-inch perimeter void requires precise polymer engineering. ### High-Expansion vs. Low-Pressure Formulations: - **Standard Expanding Foam:** Formulated for general gap filling. Generates intense expansion forces that crush vinyl jambs, binding sashes and popping balance springs. - **AAMA-Approved Low-Expansion Foam:** Specially formulated closed-cell polyurethane that exerts minimal curing pressure. It cures into a flexible, closed-cell microcellular foam that maintains an airtight thermal barrier without bowing jambs. ServiceFind Windows Pro technicians use only certified low-pressure expanding foam systems. Call for a **Fair Quote**.