High performance custom vinyl replacement windows from Castle Windows perform above and beyond the industries highest levels of energy saving technology. By incorporating our newest environmentally safe water injected foam into the sash and frame members of our windows along with optional high performance glass packages, Castle Windows has out distanced the competition in overall product performance. Our Natural Foam increases the large frame profiles from an R-5, hollow extrusion, to an R-25! That's five times more efficient than window frames without Natural Foam. This environmental safe product from Castle Windows will provide you many years of comfortable living insulating against heat and cold that is above and beyond all the rest. You are here: Home >> Product Catalog >> Foam Filling