Metal Roof Top Chimney
Modern homes often include prefabricated fireplaces. These fireplaces connect to prefab chimneys. At its most basic level a prefab chimney is a metal pipe that runs up past your roof and allows exhaust gases to exit your home. There are many ways to tell if you have a prefabricated chimney. The easiest way is just to look. If, roughly over your fireplace, you have a metal pipe coming up out of your roof and you do not see a brick chimney then you have a prefab chimney. Also, you can look inside your fireplace. If the top of your fireplace is connected to a metal pipe then your chimney is going to be a prefab chimney. A prefab chimney does not need a flue liner and only connects to one appliance. This is why modern homes often have multiple steel pipes visible on their roofs.
Prefab chimneys require a specific style of chimney cap dependent upon the type of piping used for the chimney. Pipes come in essentially two varieties; Solid Insulated or Air Cooled. If your chimney looks like a larger pipe with a smaller pipe inside and has an open gap between the two pipes then it is air cooled. For air cooled pipes be sure to use a cap designed to allow that air flow to continue unhindered. Solid pipes can use standard caps.