Worsted and woolen wool are both from sheep. Their main difference results from the spinning process. The worsted spinning system yields highly twisted yarn, while the woolen spinning process results into more bulky and looser yarn. When weaving fabrics the worsted yarn can be woven very tightly, and results in a flat fabric. The bulkier woolen fabric has a higher insulation due to more entrapped air. Consequently, worsted wool garments are best for spring, fall and warm winter climates. Woolen fabrics are best for cold climate winters.