WOOL OR SILK……Hobbs makes wonderful wool batting that can be machine washed, and does not need to be densely quilted……I used their wool in the quilt I did for my Brother and SIL last year……they heat their entire 3 story Victorian house with the fireplace (no insert) in their living room - so bedrooms get cold……but they love their quilt and say they have a thin cotton blanket over the sheet and under the quilt, and need nothing else.