The expansion vessel membrane market is projected to grow from US$2.9 billion in 2025 to US$4.1 billion by 2032, with a 5.9% CAGR. The market is driven by increasing urbanization, industrialization, and the growing demand for water and HVAC systems, particularly in Asia Pacific. EPDM rubber dominates the market due to its heat resistance and durability, holding a 45% share. Fixed membranes, favored for residential and small commercial applications, account for 65% of the market. Innovations in materials and the rise of renewable energy systems, such as solar thermal, further fuel market growth. Asia Pacific is expected to lead, with a projected CAGR of over 7%.