Abstract: An insulated construction block incorporates improved insulating features which minimize thermal conduction through the block itself and through mortar joints between adjacent blocks in a masonry wall. The block includes a recessed end face designed to receive an insulation insert in a vertical mortar joint between adjacent blocks and to maximize the amount of insulation in the mortar joint. The recess overlaps interior insulating spaces within the construction block to minimize heat loss through the end walls of the block. The insulating inserts received in the mortar joint and interior insulating spaces are greater in height than the block to project into the horizontal mortar joints above or below the block.