A heat exchanger system includes a heat exchanger coil, a base of a foam structure including a clamp with a first arm and a second arm, where the first arm and the second arm are configured to exert a clamping force against the heat exchanger coil, and a vertical member of the foam substructure coupled to the base and abutting a cover of the heat exchanger system, where the base and the vertical member are configured to block air flowing through the heat exchanger from flowing into a void between the heat exchanger coil and the cover.