Cold box. The cold box includes an enclosure comprising insulating walls having a first selected R value per surface area defining an interior space. A cold pack is located in a central region of the interior space and insulating material having a second R value per surface area is adjacent the cold pack forming a cold chamber within the interior space for receiving a substance between the insulating material and the insulating walls. The ratio of the first selected R value per surface area to the second selected R value per surface area is chosen to maintain temperature in the cold chamber within a selected range.
