Duvets can reduce the complexity of making a bed, as they can be used without a top sheet, blankets or quilts, or other bed covers. Duvets can be made warmer than blankets without becoming heavy. The duvet itself fits into a specially made cover, usually of cotton or a cotton-polyester blend. The duvet cover can be removed and laundered as often as the bottom sheet and pillowcases. It can also add coziness to your bed.