We’re on an industrial level, so we need insulated wood. The only way to keep churning out building materials at a big scale and fast rate is by using insulated wood and black ice; the amount of stone and time required to supply our needs would just be prohibitive, so blonde planks and chilly rocks it is!
We still use hardened bricks to decorate the inner layer of our base with Aquilonian and Argossean fence foundations and ceilings, though. We might be barbarians living in a huge fortress-bunker in the desert, but that doesn’t mean we can’t indulge in some luxurious marble to balance out the otherwise absolutely Spartan and efficiency-oriented building.