Wool is a natural fiber that is superior for clothing than any synthetically created fiber.   

Wool is a biological fiber that chemically reacts to meet varying environmental needs.  Thus explaining how a fiber that insulates and maintains warmth in cool temperatures has the ability to provide cooling comfortableness during warm temperatures.  Wool is an amazingly versatile natural fiber that repels moisture and yet also absorbs and evaporates moisture.  

Properties of Wool

Creating a Superior Diaper Cover

Breathable

Antibacterial: the lanoline added to your cover to enhance its water-repellent nature has antibacterial and anti-fungal properties

Naturally Water-Repellent: the structure of the wool fiber makes it water-repellent.  The lanoline that is used to coat the fibers will add to its water-resistant properties.

Absorbs and Evaporates Moisture

Temperature Regulator

Doesn't Retain Odors

Dirt-Resistant

Naturally Fire-retardant 

Strong-Elastic Fibers: When properly cared for wool diaper covers can last for your diapering years.

Resists Static Build-Up

If you are intrigued with the wonderful properties of wool and would like to read more about the science of wool fibers, I suggest reading the following articles:

Why Use Wool For Diaper Covers?

Wool Fabrics

Diaper Covers: Why Wool's Cool