Get an el-cheapo Dogloo. Heave some cedar shavings in there and witness how a GSD ignores the cold. Ever wonder where the calories go with dogs? They (should) eat about 2x the calories we do. That energy has to go somewhere and generating body heat is one of the ways.
The key is to create an area with little to no air-flow that the dog can curl up in. Their bodies crank out enough heat to keep them comfy. If you are very interested in the subject, have a look at the vein structure in a dog's paw. It's "wired" so that the veins act as a heating jacket.
Never cook bacon while naked.