I used to help raise and tend to chickens during my childhood. As adults chickens have an outer layer of stiff feathers on their wings and back which mainly function as protection against moisture and enhance mobility (fluttering, gliding, etc.), but beneath this layer there's a layer of very soft down feathers which offer insulation against the cold. It's best to feel how soft their down feathers are when they're chicks, as their stiffer feathers haven't grown in yet, but also if you spend a lot of time reaching under hens for their eggs you'll find that their undersides still have a lot of softer feathers for nesting purposes.