To sleep comfortably and have a refreshing sleep, you should be warm enough with a mild and dry temperature.  The moisture given off by the body in the night can go up to several hundreds of grams per person and has to be removed. Wool makes this exchange perfectly, it keeps the body warm and removes perspiration via its fibres.  

To convince yourself just take a piece of wool, put your hand on one side and blow on the other side of this bit of wool holding it near your mouth. You find that the warmth stays near your mouth and that your hand is moist on the other side. 

To achieve this result you need a high-quality thick and durable WOOLMARK woollen cover with long, soft fibres that ensure total comfort.