The best methods for flue installation include ensuring all chimneys are properly insulated and incorporate as few bends in the piping as possible; only fire resistant materials should be used for the project as well. Most flues should be installed by building contractors to best prevent house fires. Home owners often can attach new stove units to existing insulated flues that have been examined and approved by a home safety inspector prior to use, however.
The term flue is used to refer to any type of piping that conducts excess heat and harmful gases away from home heating units. They are typically used with fireplaces, water and oil heaters, and wood burning stoves. A flue may be made from metal piping or mortar and brick. A mortar and brick chimney should only be installed by contracted professionals, but many types of metal piping may be added to existing homes by the home owner.
The first step in proper flue installation is to ensure that the length of the chimney is properly insulated. This will funnel hot air away from the other building materials of the home, prevent warm air from escaping the home through the flue, and protect the breathable air of the home from becoming contaminated with toxic gases. The flue may be insulated with a chimney liner, which should generally be installed by a chimney repair expert, or covered in a chimney skin, which can be purchased from a home repair center and installed by a homeowner.
When adding a wood burning stove or gas heater to the home, the easiest method for flue installation is to connect the new unit to an existing chimney through the use of a stove pipe. If no chimney is already present in the home, a contractor may install insulated chimney piping to which the new unit may be attached. This type of piping must meet local safety home building codes and extend several feet above the roof of the house. Metal stove piping should never run directly through any walls or ceilings within the home, as this can present a fire hazard.
Only materials that are labeled specifically as safe for use in direct contact with extreme heat temperatures should be used. Mortar and brick flue installation and repair typically requires fire resistant mortar and insulating ceramic tiles. Metal chimneys are made of steel and iron piping designed to resist vaporization at high temperatures. Most metal chimney materials are painted black for these purposes.
The second step in flue installation is to determine what size chimney is required for the heating unit and how many joints it will need. Most water heaters and wood burning stoves that are purchased from home improvement stores will list in the instruction guide the chimney size required to properly vent the unit. Enough piping should be purchased to span the length between the top of the stove or heater and the vent leading to the outside. The heating element should be located relatively close to the vent and use either one 90-degree joint or two 45-degree joints to connect the two. This will create a natural draft that pulls harmful gas out of the stove and blows it through the venting system.
Flue joints also should be overlapped during installation, allowing for some heat expansion during use, to prevent fumes from leaking into the home. These joints, which occur at pipe connection points and at the flue collar, should overlap by a minimum of 1.25 inches (about 30 mm). Both ends of the piping should then be fastened together by three or more metal screws.
The safest type of flue installation is to allow the entire unit to vent upward through the home without the use of intervening joints. This eliminates the possibility of leakage or corrosion to occur within the unit. When possible, the insulated chimney should attach directly to the heating unit and vent through the roof of the house. This type of system is not usable in houses that have a large attic space, however.