[whatshisface]

As of the last time I heard, SpaceX was planning to use an extremely aggressive active cooling system: cold fuel would be bled through many holes in the hull, in a process similar to sweating. The hull may never get above room temperature.

[SECProto]

No, the "sweating methane" cooling is no longer happening (per the presentation/q&a last night). Instead they're using ceramic insulating heat shield tiles - similar to the shuttle, but different materials, very different attachment mechanism, and a regular shape (tiles will all be hexagonal)