What to use for walls in unheated room?

For unheated rooms, consider using materials that provide good insulation and moisture resistance. Rigid foam board insulation can be a suitable choice, as it helps prevent heat loss and moisture buildup. Alternatively, using plywood or oriented strand board (OSB) can offer durability while allowing for some insulation if combined with proper insulation materials. Additionally, ensure proper ventilation to prevent dampness and mold growth.