Can anyone tell me if there's a point to upgrading from dirt to stone or brick for cellars?

[Nerdlin Geeksly]

Does using say stone blocks or clay/cobblestone bricks work better at insulating than dirt?

[Jack Mackey]

It's been a while since I tested this, but from what I remember packed dirt/cobblestone/etc. insulates the same. I didn't test wood, but people frequently mention it is less effective than dirt and stone.

I always suggest people make a creative world to test things like this if the information isn't readily available.

 

[Streetwind]

No, there are no material grades. Either a material is suitable, or it is unsuitable. The ratio of suitable to unsuitable blocks determines how good a cellar performs, meaning a cellar made up of 100% suitable blocks has perfect stats and cannot be improved any further by switching materials.