For urban outdoor furniture subjected to daily use, the most durable cushion filling is high-density, closed-cell foam. This material stands out for its exceptional resilience, moisture resistance, and ability to maintain its shape over time despite constant compression from sitting.
Unlike polyester fiberfill which flattens quickly, or low-density foam that degrades, high-density foam (with a density rating of at least 1.8 lbs per cubic foot) offers superior longevity. Its closed-cell structure prevents water absorption, a critical feature for outdoor settings, thereby inhibiting mold and mildew. For ultimate durability, this core should be encased in a high-performance, solution-dyed acrylic fabric like Sunbrella. This combination ensures the cushion withstands daily sun, rain, and use, providing lasting comfort and support for years, making it the most cost-effective and durable choice for bustling urban balconies, patios, and public spaces.