Chimneys, Vents and Connectors: a Guide
On part two of our guide to chimneys, vents and connectors, we will be covering the specific types of chimneys, vents and connectors. Refer to our initial chimney terminology guide for more general information on chimneys, vents, connectors and flues.
Types of Chimneys
There are two major types of chimneys: masonry and factory made. Masonry chimneys are made of brick or block and require lining for proper safety. Stainless steel liners are preferred.
Factory-built chimneys are often referred to as “class A chimneys”. This terminology is not official, but chimney professionals use it and understand its meaning. Class A Chimneys always have a stainless steel interior and a galvanized or stainless steel exterior. If the class A chimney runs outside without a chase, stainless steel is always used.
Class A chimneys are insulated to prevent the outside of the chimney from becoming excessively hot. There are two types of insulation used: packed pipes and air insulated pipes. Packed pipes have a double wall with insulation between the layers to help absorb the heat. Air insulated chimneys can have up to three or four walls without insulation between them. In these chimneys the air space is used to help absorb the heat. These may also be called “Air Insulated” chimneys.
It’s worth noting that Class A Chimneys must always be used as a whole unit. Mixing parts from different brands/makes is extremely dangerous and strictly prohibited.
Types of Vents
Vents are used for the venting of gas, oil and bio-mass appliances. They are never used as a chimney for a solid fuel such as wood. While using multiple brands isn’t optimal, adapters are sold to allow the use of pipes from multiple vent brands.
Type B Vents are factory built double wall vent pipes that are only used to for venting gas. They are always made with a galvanized exterior and an aluminum interior. The air space between walls is fairly small. This vent can be used as a vent or connector, and is quite inexpensive.
Type L vents can be either a vent or a connector, and is made to vent oil. Class A chimneys are still preferred in the market over L vents, and as such L vents availability is limited. Sometimes it is listed for “bio-mass venting”, or venting the products of combusting pellets, corn, cherry pits, etc.
Pellet vents are technically L vents as well. These vents must be installed through a house or be in a chase. While they have stainless steel interiors, their exterior may be black or galvanized steel.
Types of Connectors
Type C vents are used only as connectors. They are single walled galvanized pipes, and as such often called “galvanized pipes”. They are used only for venting gas or oil. Using a C vent with solid fuel appliances can cause extremely toxic fumes. This is the least expensive of the pipes. Inspectors mandate that when used, C-vent crimps must go away from the appliance towards the chimney or vent. This isn’t an official rule and there’s no specific reason for this to be necessary, but is simply a standard on installation. Inspectors will make you reinstall the vent with the crimps pointing the ‘correct’ way, so it’s best to just install them appropriately from the beginning.
Black single walled pipes are also only used as connectors. Sometimes they are referred to as “black galvanized pipe” even though it is not galvanized. While black single wall pipes can be used for solid, gas, or oil venting, it’s expensive and overkill for gas and oil. To prevent condensing creosote from leaking out of the pipes, crimps must point to the stove. This isn’t an official rule, but it is a best practice is you don’t appreciate the smell of creosote.
Double walled stovepipes are used for reduced clearance solid fuel, and used only as a connector. They’re more expensive than single walled stovepipes as they are made of double walled pipe with an air space insulator.
When making decisions about vents, connectors or chimneys, it’s always wise to work with an experienced chimney and vent specialist. They can help you navigate installation to ensure your work passes inspection, looks great, and works well for years to come.