Single-wall stove pipes can be installed from a stove to within 18" of any combustible material. Double-wall stove pipe has the same application but with clearances down to 6" from wall combustibles and 8" from ceiling combustibles. Neither single nor double-wall stove pipe can be used to penetrate ceilings, walls or roofs.In a vertical chimney pipe installation, stovepipe runs from the stove to a ceiling box designed for a flat or cathedral ceiling. Insulated pipe goes through the box, through an attic or second floor if applicable, through the roof and up to a rain cap. In a horizontal installation, a wall box is used and the insulated vent pipe goes through the wall and up the exterior of the building to a rain cap.The function of the insulated double- and triple-wall chimney pipe is to protect adjacent building structures from the high temperatures created by high-output appliances. To do this requires that the pipe remain cool on the outside by having an internal design that creates a fire-safe venting system. Manufacturers use different techniques to achieve this. Chimney pipe may be air cooled, have insulation packed in the gap(s) between the pipes, or have a ceramic insulating blanket in conjunction with the gap(s). The goal is to minimize the outside diameter of the pipe and the allowable distance from combustibles. This can be 2" for double-wall pipe and 1.5" for triple-wall pipe. The outer wall of chimney pipe is stainless steel or galvanized steel. The inner wall is stainless steel. In three-wall pipe the intermediate wall is aluminized steel. Rockford Chimney Supply offers Rock-Vent and Selkirk Class A insulated chimney pipe systems.Double-wall insulated pipe is listed as Class A vent pipe and must meet certain UL standards. Double-wall requires pipe capable of safely operating with an internal temperature up to 1,200 degrees Fahrenheit and withstanding a maximum temperature of 1,700 degrees Fahrenheit. Triple-wall insulated pipe has the same application as the insulated double-wall, but with different temperatures and clearances. Triple-wall requires pipe capable of safely operating with an internal temperature up to 1,700 degrees Fahrenheit and withstanding a maximum temperature of 2,100 degrees Fahrenheit.