Outside at the top of my chimney there are to openings exposed to rain. Do I need to cover them and why. I have never had problems with water, but I am concerned living in a very rainy area as to where the rain that does get in goes. My observation of other chimneys in the area is that some have various covers, others do not. Do I NEED to spend the money to cover them or is the chimney designed to take on rain?