 Some hammocks are designed with an extra layer of fabric, or a series of large pockets, on the bottom.Insulating material, such as foam, quilting, aluminum windscreen reflectors, clothes, or even dead leaves and brush from the campsite is stuffed between the bottom layers or inside the bottom pockets to create a buffer between the camper and the cold outside air.While the above solutions, except for the found materials, add weight and bulk to the hammock, some approaches use an ultralight open cell foam with a mylar space blanket to mitigate this increase in weight.