3 Different Types of Gas Furnace Vent Pipes Explained

For many homes, a gas furnace is the preferred heating device. It has proved to be an efficient and reliable way of meeting household heating needs over the years. The vent pipe or flue is a vital component of the furnace. It transmits emissions from the combustion process out of the building. This ensures that those in the building are not harmed by toxic gases and other byproducts of combustion. The flue is also a safeguard against fire. If the waste gases come into contact with other combustibles, a fire can easily break out. Below are 3 types of venting for gas furnaces.

Natural Vent

It operates on natural air convection and is also known as the Type B vent. Type B vents are a standard design. Most modern gas furnaces incorporate the B vent. It draws air from within the house for combustion. Gases produced during combustion are very hot and so easily rise through the flue. The air is then vented outside through a B-vent pipe which is set vertically to expel combustion air through the roof. Natural vent pipes can be installed fairly easily. Costs are also fairly modest which makes them a popular choice. However, back-drafting is more common with natural vent pipes than other varieties. The indoor air can easily pull back combustion gases indoors. This detracts from the efficiency of the B-vent piping. The tendency to back-draft also raises questions over furnace safety where such pipes are used. Back-drafting can affect the health of household occupants through inhalation of toxic emissions.

Direct Vent

It is an ideal alternative to natural vent systems. The piping system incorporates two pipes of different sizes in one unit. The outer pipe draws air for combustion from outside. The smaller pipe occupies the inner position and is used to vent the exhaust fumes. Piping can be set horizontally to allow venting through a sidewall. Vertical installation of piping can also be undertaken to allow venting through the roof. These options add to the installation versatility of direct vent systems. No chimney is needed whether horizontal or vertical installation is used. Installation is fairly easy. Less environmental pollution occurs with direct venting since they extract most of the combustion heat and expel it outside. They do not spoil the quality of indoor air unlike the B-vent type.  Safety ratings are also higher for direct vent furnaces than the natural vent type. However, installation of direct venting is more costly than the B-vent type.

Sidewall Power Vent

This is also referred to as an induced draft fan. A fan is placed at the end of an exhaust pipe that runs through a sidewall. It draws out combustion gases and expels them outside. The fan works in conjunction with the furnace. It usually turns on before the furnace starts. Sidewall vent systems are especially great for replacing old chimneys. It is one of the more affordable options when considering venting systems to install for your gas furnace. Sidewall power vents also rate highly in efficiency and safety.