One-sided, insulated formwork used in the construction of walls from pourable building material, such as concrete, including an insulating panel connectable to a removable panel by a connecting structure, which may include a permanent reinforcement embedded in the insulating panel. The connecting structure may have a tie removably attachable to the reinforcement, or the reinforcement and tie may constitute a monolithic structure. The tie may be asymmetric in shape to facilitate distribution of loads across the insulating panel, detachment of the removable panel, and enhance the structural integrity of the finished wall.