A modern masonry wood-burning fireplace with a factory built metal Class-A chimney system
Many homes that are (or were) heated with wood or fuel oil, or back in the day, coal, have (or had) masonry chimneys to move the exhaust from burning those fuels to the outside. The chases used to hide these chimney systems are often areas of very high air leakage into and out of a home. With the advent of modern heating equipment that more efficiently burns natural gas and propane, or a system that doesn’t use any burning fossil fuels inside the home to produce heat, such as electricity, the old masonry chimneys have all but gone by the wayside. I have been in many homes, including my own, where the use of this type of chimney system has been discontinued. Mine no longer extends through the roof; it terminates in the attic space. Others have been completely removed. Some new homes being built today still have chimney systems, the masonry chimney is rare, most install metal chimneys or use PVC vents.