What type of exhaust system do I need?

Your exhaust system is comprised of two main elements: a chimney and a connector (commonly called "stove pipe").

Connectors are simply steel pipes that connect the appliance to the insulated chimney. They are normally needed unless the appliance is already inserted into an enclosure (for instance, in the case of a zero-clearance wood fireplace). Connectors do not pass through combustible materials. The term “black pipe” is also often used in the industry. There are two types of connectors: -Single-wall pipes
-Double-wall pipes

As their name indicates, single-wall pipes have just one wall. A minimum of 18 inches is required between the pipe and a combustible wall. In general, single-wall pipes provide less insulation than double-wall pipes do and therefore require more clearance. This is the main drawback of single-wall pipes. Their advantage is in their cost; they are nearly three times less expensive than double-wall pipes.

As their name indicates, double-wall pipes have a second wall, i.e., an interior one made of stainless steel. The cushion of air between the two walls provides thermal insulation allowing the appliance to be installed much closer to walls. This is the main advantage of double-wall pipes. The required distance for each heater model is based on the safety tests conducted with each type of connector. You therefore need to properly consult the appliance’s owner’s manual in order to know the prescribed clearances from combustible materials.

Chimney
There are two types of chimneys: an insulated (or prefabricated) chimney or a masonry chimney. If you have a masonry chimney, it must meet the local building code. It must be lined with refractory bricks or tiles joint together with refractory cement. The chimney diameter should be the same as the appliance’s flue outlet (6 inches for most models). It is rarely the case with masonry chimneys. Their diameter is often bigger than the appliance’s flue outlet. The way to deal with this is to insert inside the masonry chimney a stainless steel liner that has the same diameter as the appliance’s flue outlet. Unless a liner is installed, serious draft problems can occur.

An insulated chimney (or prefab chimney) is a stainless steel flue that has been tested to resist temperature as high as 2100F. It has a double wall filled with insulating wool. The majority of insulated chimneys have 2 inches of insulation, while some have just 1 inch. Others are air-insulated and have 3 walls; they are referred to as “triple-wall air-cooled chimneys. When we speak of a 6-inch chimney, we are referring to its interior diameter. If the chimney has 2 inches of insulation, the flue will have an exterior diameter of 10 inches.

In wood-heat system installations, we must use an insulated chimney for any flue that passes through walls, ceilings, attics and closets (i.e., all combustible surfaces in general). This chimney must also be installed outside the house.