Constructing durable buildings in year round humid coastal regions with heavy monsoon rains and salt laden sea breeze requires wall materials that resist moisture damage and salt corrosion, and the EPS Cement Sandwich Panel is engineered to perform reliably in these harsh environments. The dense low porosity fiber cement face boards of the EPS Cement Sandwich Panel have extremely low water absorption, preventing rainwater salt spray and coastal moisture from seeping into the wall structure and reaching the inner EPS core. Unlike ordinary drywall that swells softens and crumbles after prolonged exposure to high humidity, this panel stays completely dimensionally stable with no warping deformation or strength loss even after decades of exposure to coastal weather. The EPS Cement Sandwich Panel also naturally resists mould mildew and fungal growth that commonly plagues walls in tropical humid climates, preventing dark ugly stains from appearing on interior wall surfaces. The anti corrosion treatment on the panel internal connectors prevents rust formation even in high salt air environments, eliminating hidden structural damage that can compromise wall safety. Builders can install these panels for exterior facades and interior walls in coastal residential vacation homes and seaside resort facilities. This EPS Cement Sandwich Panel drastically reduces long term wall maintenance and repair costs that usually come with building in high humidity coastal locations.