It is important to protect your chimney from rain and snow. Water penetration can cause interior and exterior damage to your home and chimney. I think chimney caps are the most inexpensive preventive measure to prevent water penetration and damage to the chimney. You can buy these caps from http://www.chimneygenie.com, or near your locality. Chimney caps also provide other benefits. It prevent birds and animals from entering and nesting in the chimney. Caps also function as spark arrestors, preventing sparks from landing on the roof or other nearby combustible material.