Insulation: ice house on Tentsmuir Point

We found this ice house on Tentsmuir Point near St Andrews. These date from the days before freezers. The idea was to have ponds nearby that froze in the winter. They cut ice on the ponds and filled the building. The building must have been very well insulated. The large mass of ice would mean that a lot of energy would be needed to change its temperature. Water has a high specific heat capacity. Ice has about half the SHC but that is still quite high. Since energy needed = mass x SHC x temp difference, a large mass sort of means "safety in numbers" for the ice. Also there is the energy needed to melt the ice once it reaches 0 degrees Celsius - the specific latent heat. Provided the insulation is good, the rate of flow of thermal energy inwards is too small to melt the ice. The ice would stay frozen until next winter. It was used to freeze fish to keep them fresher for export. I would have liked to have been able to get in to see how the door prevents too much hot air getting in every time it is opened.