Chimney caps are available in a variety of materials, including stainless steel. The chimney cap design and construction material that is right for your chimney depends on a number of factors, including the types of fuels your chimney cap will be venting combustion gases from, the aesthetic effect that you want your chimney cap to have, and the amount of money you want to spend on it.
A good chimney cap is a critical element in your total chimney system. A chimney cap with screened sides will reduce fire danger by acting as a spark arrestor. It will keep birds and other small animals from entering your flue. The masonry crown on your chimney will have less weather damage if a chimney cap sheds precipitation before it can seep into cracks in the masonry. A chimney cap will keep rain and snow from running down your flue and damaging your heating appliances.
In addition to the material you want for your chimney cap, you also need to consider other design factors. You may need a cap to cover more than one flue on top of your chimney, or you may want your chimney cap to also double as a top-seal damper when your fireplace is not in use. Some chimney caps are specially designed to improve chimney draft.
Aluminum, galvanized steel, copper and stainless steel are the most commonly used metals in the construction of chimney caps. If your chimney will be venting gases from appliances that burn fuel oil, you will want a chimney cap made from a highly corrosion resistant material like stainless steel. Along with water vapor, sulfur is a common element carried in the exhaust from fuel oil burning. These combine to form sulfuric acid, which is highly corrosive to plain steel or aluminum if it condenses on the chimney cap surface.
Aluminum and galvanized steel chimney caps are less expensive than stainless steel or copper, but you should expect them to have a shorter useful life regardless of what type of fuel you burn. Exposure to intense sunlight, winter and summer temperature extremes and acidic moisture from the chimney all make these caps more likely to corrode than stainless steel caps.
Stainless steel caps do not cost a great deal more than aluminum or galvanized steel chimney caps, but they should last a lot longer and require very little maintenance. Stainless steel caps are commonly available in the unfinished stainless steel color and in black paint, so you can choose a color that fits your home’s décor or your personal taste. The black painted stainless steel chimney caps will hide any black soot or creosote that accumulates on their surfaces, so they provide a continuously attractive top to your chimney.
For an elegant look that matches some building styles, a copper chimney cap might be the right choice. Copper is more expensive than stainless steel, but if it is properly cared for it will give you many years of beautiful and effective service. For most homeowners, though, considering cost, ease of maintenance, and long life, stainless steel chimney caps might be the best overall choice.