All flues require animal proof rain caps, either through code or through common sense. Animal intrusion is always a risk and the damage caused can by very high. Rain, on the other hand, is guaranteed to damage your chimney. Masonry chimneys are susceptible to spalling, which occurs when the water is your masonry expands and contracts due to the freeze/thaw cycling that happens during Canadian winters. Stainless steel chimneys do not like water at all, in fact, even pinholes can render a section of stainless steel chimney useless. The insulation inside these chimneys becomes highly corrosive when wet.
All of our covers come with a lifetime guarantee. Please see Animal and Blockage Removal for more information.