What is best way to insulate cement block basement walls that are above grade?

The best way to insulate above-grade cement block basement walls is to use rigid foam insulation boards, such as extruded polystyrene (XPS) or polyisocyanurate. These boards can be adhered directly to the wall surface, providing an effective thermal barrier while also resisting moisture. Additionally, sealing the joints with spray foam or tape enhances energy efficiency and prevents air leaks. For added protection, consider covering the insulation with drywall or another finish for fire safety and aesthetics.