I am trying to find ways to build more effective freezers. I already know that creating thicker walls helps to reduce heat dissipation, but are there better materials in term of insulation? Which ones?
Unfortunately, it doesn't look like material type has any effect on insulation value. The only way to improve walls' insulation is to make them thicker.
A user here did a test to check how insulation worked:
"2 Wall" means the freezer was surrounded with a double thick wall. "2 Door" means that there are 2 doors in series with each other to enter the cell, not that there are two separate entrances.
As I expected, wall material has no effect on insulation. Also, the best insulation comes from having a double thick wall. Doors can significantly increase the heat transfer, even when not in use.
This was tested on an extreme desert map in the summer. Each test cell was cooled to -20 F and steady state, then power was cut to the coolers and temp was plotted each hour.
Another thread here also supports this:
Item stats have no effect at all.
However, double-thick walls will insulate better.