Prefabricated fireplaces are more and more common because they are less expensive to put in a home as opposed to a masonry fireplace. A prefabricated fireplace relies on a prefabricated chimney flue to vent the fireplace.
There are two main types of prefabricated chimneys: air cooled chimneys and insulated chimneys (often referred to as solid-pack or non-air cooled). Each pipe requires a different type of chimney cap. If you look up at your chimney and you do not see a chimney rain cap on your flue, then a cap should be installed immediately to prevent costly repairs down the road.
So how do I tell if my chimney is an air-cooled chimney or an insulated chimney?
Air cooled chimney pipes are easy to identify. Air cooled chimney pipe will be a double wall or triple wall pipe. When you look down the pipes you will see all the layers of the pipe and there will be an air gap between the pipe. If your rain cap is still connected and you wish to replace the cap, you will likely have to remove the rain cap to identify if it is an air cooled chimney cap. In some cases you can hit the outside wall of the pipe with a screw driver and if you hear vibrations and the sound rings out, then it is likely you have an air cooled chimney pipe. However, taking the chimney cap off the flue pipe is the best route. Two universal types of air-cooled chimney caps include Weathershield TDW and VacuStack TDW.
Insulated solid-pack chimney pipes are also easy to identify. The insulated chimney pipe can also be a double or triple wall pipe, however it will appear as one solid pipe. The insulated chimney pipe generally has a wall thickness of one inch. Unlike the air cooled pipes, you will not be able to see the layers of the chimney pipe if you have solid-pack insulated chimney pipe. Sometimes you can tell if you have an insulated pipe by lightly hitting the outside wall of the pipe with a screw driver. If you do not hear any vibrations, it is likely you have an insulated pipe. Again, taking the chimney cap off the flue pipe is the best route. Two universal types of solid-pack Class A chimney caps include Weathershield WSA and VacuStack.
Now that you know what type of chimney pipe you have, picking the correct chimney cap is simple!
A chimney rain cap is an important part of a prefabricated fireplace and chimney. A chimney rain cap will not only keep rain out of your chimney, but also debris and critters. The chimney cap will also prevent costly repairs to the chimney flue and most importantly keep the top of the prefabricated firebox from rusting.