An insulation layer is a material or substance that is used to keep something warm or cold by preventing the transfer of heat or coldness. It is like a protective barrier that helps maintain temperature. Full definition
They are great to add an extra insulation layer in winter or cover - up on a chilly evening. (highlatitudestyle.com)
This pack also comes with a hydration insulation layer that works well with any 2.5 L hydration bladder. (geekwrapped.com)
Double coats are like our winter coats with an interior insulation layer to prevent loss of body heat and an outer layer to block wind and rain. (dogcare.dailypuppy.com)