A MASONRY CHIMNEY can be one that is made or constructed out of brick, concrete blocks or stone. Usually this chimney has a clay tile with no insulation. They may be exterior or interior chimneys. An exterior is completely outside the exterior wall of the building, excluding the soffit area. Exterior must have a minimum unfilled air space clearance of at least one inch between combustible materials. Interior chimneys have some portion of the chimney located within the exterior wall of the building and require a minimum unfilled air space clearance of at least 2 inches between combustible materials.
FACTORY BUILT CHIMNEYS are manufactured in a factory and assembled and installed at the site. They are made up of components such as Double wall insulated chimney system. Quality and design uses a thermal tech blanket insulation which keeps the outer wall of the chimney pipe cool. Picture a smaller pipe inside of a larger pipe with about 1 inch of space between them all around. It ensures high flue gas temperatures for optimum draft performance. It also eliminates hot spots common with loose fill type insulation, no shifting or settling.
In the event of a chimney fire this compressible blanket insulation permits the chimney liner to expand outward. The free floating inner liner design also permits the liner to expand lengthwise, eliminating buckling and the loss of structural integrity. Double wall is made of a stainless steel inner liner and outer casing generally stainless steel.
AIR COOLED CHIMNEY is usually made up of more than two layers of metal. They differ in design from air insulated chimney. They normally use three layers of chimney to create two air spaces between the flue and the outer casing. Triple wall are designed to set up a steady flow of air between the two spaces. The air in the inner space picks up heat from the flue and rises to the top of the chimney. As it rises, it draws in cooler air from the outer air space. This continuous convection pattern has the effect of cooling the flue. Because heat is removed to the top of the chimney the outer wall of the chimney stays cool. The cooler flue liner results in cooler flue gases. A factor that might tend to increase creosote build up.
AIR INSULATED CHIMNEY SYSTEMS use three chimney walls for all fuel types. It is a triple wall chimney that combines one layer of ceramic refractory blanket insulation and an air space to keep the outside wall cool. With the added insulation it keeps the inside wall hot for better efficiency. It has a fire safe design that allows the hot metal to flex and expand while it cools the chimney. Usually it is made up of stainless steel, galvanized steel or aluminum materials.