The Dynamic Hohlraum (DH) radiation on the Z facility at Sandia National Laboratories is a bright source of radiant energy that has proven useful for High Energy Density (HED) physics experiments. To be useful for HED experiments, where computer simulations need to be compared with experimental measurements, the radiation output from a DH on Z needs to be well-known. We present in this paper a new method for measuring the delivered radiation energy deposited in an experiment, specifically, an experiment driven by a Z DH. This technique uses a blast wave produced in a SiO 2 foam, which is initially super-sonic but transitions to sub-sonic, producing a shock at the transition point that is observable via radiography. The position of this shock is a sensitive measure of the radiation drive energy from the Z DH. Computer simulations of been used to design and analyze a Z foam blast wave experiment. This experiment has been shot on Z and experimental results compare favorably with the computations.