Squirrels sleep in leaves in the winter. Birds use sticks to build nests. People use styrofoam to insulate their houses. Straw is an insulator. If you jump into a haystack, it will warm you up.
Dirt can keep animals warm.
Fiberglass is in my mom's truck. Fiberglass makes people itch. I have a blanket to sleep with. They insulate by trapping the air in. Carpets are fluffy so they can trap air.