For the same reason you have a roof over your house, you should have a chimney cap over your fireplace flue. Having a chimney cap is one of the best investments you can make for your chimney. A chimney cap is installed onto the top flue tile of your chimney and provides a screen around the sides and a cover on the top.

By having a chimney cap installed you are preventing any direct weather damage from speeding up the process of deterioration in your flue and fireplace, a chimney cap will also prevent any critters from feeling the warmth of your flue (even if you don't use your fireplace) and crawling in and making a home.