There are six main types of vent pipes, each with its own purpose and construction. One might wonder how to differentiate them from other venting products. The term "chimney pipe" is often misused to refer to all types of ventilation pipes, but it actually refers specifically to the Class A chimney pipe used for wood-burning applications. The six types of vent pipes are Class-A Chimney Pipe, Stovepipe, Pellet Vent Pipe, Gas Vent Pipe, Type-B Vent Pipe, and Direct-Vent pipe. Although they share similarities in construction and appearance, Class-A Chimney is designed for wood-burning applications and certain models of multi-fuel hearth appliances. This section provides an overview of each type of chimney pipe and distinguishes their purpose by their names.
Class-A chimney pipes are designed for use with wood-burning or retrofitted gas-log fireplaces, as well as for completing the venting of a wood stove and facilitating the transition of stove pipe to chimney pipe. It is important to note that all products used in a Class-A venting system must be UL103 listed to meet safety guidelines for chimney systems. When selecting chimney pipes, it is important to choose the correct type for the specific appliance being used. Stovepipes are designed for wood-burning stoves, while pellet pipes are for pellet-fueled stoves. Gas vent pipes and Type-B vent pipes are for gas fireplaces only, and direct vent pipes (also known as coaxial pipes) are unique to direct-vent fireplaces. It is crucial to never use pellet, B-vent, or direct vent pipes to vent an appliance that is specifically rated for use with Class-A chimney. While air-cooled chimney systems may be more affordable than insulated varieties, they are typically used only with open-faced fireplaces and are rarely a suitable alternative to insulated systems. Additionally, almost all air-cooled chimney systems are proprietary and purpose-built by the manufacturer of the fireplace, so it is important to carefully consider the type of fireplace being used before purchasing an air-cooled chimney system.
Manufacturers of air-insulated chimneys use two rating systems for safety, including the Underwriters Laboratories (UL) 103 standard. To ensure compliance with this standard, standard chimney systems are rated up to 1,700°F (927°C). Chimneys must also demonstrate continuous operation at a 1,000°F (538°C) flue output, including a 10-minute test at 1,700°F (927°C). This rating is accepted in most areas of the U.S. The higher rating, UL-103HT, follows the same 1,000°F standard operating temperature but requires the chimney to endure three 10-minute chimney events at 2,100°F (1149°C). These Class-A chimneys are typically made from thicker and higher grade steel to handle hotter temperatures without damage such as warping or kinking. While some areas of the U.S. require the use of UL-103HT Class-A chimneys, they are the standard for homes in Canada.
The Class-A chimney system operates through the use of a 2-wall or 3-wall pipe system, depending on the regulations in your area. The chimney consists of an inner pipe, an optional middle pipe, and an outer pipe. The inner pipe contains heat emitted from the fireplace and carries potentially harmful combustion particles outside the home. During the burn, the fireplace creates negative pressure in the home as it removes air to create a draft up the chimney. Unfortunately, this ventilation process results in heat loss and reduced heating efficiency, which can increase the cost of your electric or gas bill. To prevent the outer wall from becoming too hot, the 2-wall system has an air jacket between the inner and outer walls, which insulates the chimney pipe. Similarly, the 3-wall system has an air jacket between the middle and outer walls. To supply the insulation air, an air-cooled chimney uses a vent cap and attachment collar located on the fireplace. The vent cap functions as an air baffle and protects against pests and precipitation entering the venting system while allowing constant airflow through the spaces between the pipe walls.
Confusing the chimney pipe insulation air with the combustion air is a common mistake. The Class-A chimney's combustion air comes either from the room where the fireplace is installed or a combustion air kit that's designed for the fireplace. The outer pipe acts as a shield for the inner pipe, preventing combustible surfaces from drying out and igniting from radiant heat. Clearance spacers or springs make sure that the recommended space between the pipes is maintained, which is typically two inches. This space allows heat to dissipate around the inner pipe, acting as a natural cooling agent that reduces radiant heat. It also prevents the outer pipe from absorbing heat emitted from the inner pipe. However, these ventilation systems face issues as they rely on outside air for insulation. Such systems perform poorly in very cold climates, particularly in extremely windy and cold winters.
The temperature outside can affect your fireplace's performance inside your home. When the inner and outer wall temperatures differ significantly, it can result in "cold hearth syndrome." This makes it harder for the fireplace to start because of the extremely cold air. Cold air is denser than warm air, and when there is a significant temperature difference, it can create a dense air pocket in the chimney. This prevents warm fireplace flue gases from escaping. The problem is worse for exposed parts of the chimney above the roof, which tend to have inadequate enclosures and insulation. If the flue gases can't escape, they will come back down into your home and pollute your breathing air. Even if the flue gases can penetrate the denser cold air, the drastic temperature difference between the chimney's walls will cause increased condensation on the inner pipe walls. This condensation collects flue byproducts, which dry into creosote. Rapid creosote buildup can cause poor chimney performance, unwanted odors, and, in severe cases, chimney fires. If you choose to install this kind of chimney, it is important to pay attention to the winter temperatures in your area. Additionally, take into account the direction of the prevailing winds. If temperatures reach or drop below zero degrees, it may be wise to opt for an appliance that can utilize an insulated chimney system.
The 3-wall chimney systems were most popular during the 1970s, but they are still in use today, although not as commonly. They were initially utilized in densely populated areas to reduce the risk of house fires spreading. The third wall in this system adds an extra safety layer for extreme temperatures. Similar to the 2-wall pipes, the 3-wall system includes a space in between the inner and outer pipes to support air circulation. 1" to 3" spacers are used to maintain the required clearances between each pipe. It is important to note that there are two different types of 3-wall systems. The traditional air insulated version is composed of three pipes that have three separate, free-floating walls held together by a vent cap. The inner pipe is made of stainless steel and is usually the same pipe used in 2 wall varieties. The middle pipe is made from galvanized steel and surrounds the inner pipe. The third outer pipe allows air flow as a natural cooling agent and surrounds the inner and middle pipe as a barrier, protecting against contact with combustible surfaces. The second type of 3-wall venting system combines elements from the air-cooled and insulated chimney systems. The first two walls are fused together with a thin layer of insulation between them, which is only approximately .25" thick. The third wall provides an open space for air-cooling. This version of piping can be an alternative for homes in colder climates, as it provides an extra layer of air space between the flue and outdoor temperatures. The selection of your chimney pipe depends on personal preferences, compatibility, budget, and climate. It is important to note that each system has its advantages and disadvantages. Based on quality and durability, the solid pack chimney system is deemed most efficient. It should be noted that only high-efficiency wood-burning stoves and fireplaces can use a solid pack or fully insulated chimney system. This claim may be controversial for regions still relying on the 3-wall venting system, but technological advances in the industry have made the solid pack chimney equally efficient.
Consider opting for a solid insulated chimney system and related fireplace or stove when temperatures reach or drop below zero. This type of chimney effectively contains heat from flue gases and is particularly suitable for colder climates where the exterior of the pipe may be exposed.
Wood appliances are now held to higher standards due to recent EPA regulations. However, sealed high efficiency wood burning appliances will remain in use for the foreseeable future. As time passes, open wood burning appliances will become less prevalent with front-sealed units becoming the norm. Front-sealed units are more attractive due to their efficiency and environmentally-friendly combustion.
The air-cooled system and insulated system differ in several ways. Manufacturers typically recommend using their own brand of air-insulated chimney, while third-party companies usually construct solid-pack chimney systems that are tested for use with appliances from various brands. Solid-pack systems are typically more expensive but are made from higher quality materials and have a smaller diameter. They are required for wood stoves and high-efficiency fireplaces due to their ability to withstand higher temperatures. Sealed hearth appliances use gasketed doors to prevent dilution air from entering during operation. Solid-insulated chimney systems have built-in insulation between a fused inner and outer wall and offer different options for the outer wall material, including galvanized steel, painted galvanized steel, or stainless steel. Installers may switch between materials for different sections of the chimney based on corrosion resistance needs and cost. Solid-insulated systems usually use 304-grade stainless steel for the inner wall due to its increased heat resistance. Insulated chimneys rely on a 1-inch thick blanket of insulation made from ceramic wool, mineral wool, or vermiculite cloth to keep the outer wall cool and prevent drying out of framing members in the home.
Installers should be familiar with common regulations related to ventilation routes and clearance requirements. It's important to follow manufacturer guidelines and consider chimney dimensions when designing a venting system. The International Code Council's website can provide more information on local codes. Two possible ventilations options are routing through an enclosure within the home or through a chimney chase along an exterior wall. Clearances for the appliance and chimney system will determine the available paths. Enclosures are different from chimney chases, which run the length of the chimney pipe and are secured to an exterior wall. Builders sometimes neglect to encase the entire chimney pipe, especially for exposed piping above the roof. Enclosures are simply interior structures built around the chimney pipe to conceal it. Sometimes, the vent pipe can be routed through a corner of a closet or similar space to make it less visible.
Consider a Chimney Chase: Although a chimney chase may require additional materials and costs for construction, the advantages it offers are worth the investment. Enclosing the chimney and venting pipes along the exterior of the home allows for greater use of floor space and prevents pipes from being visible from the outside, which can increase the resale value of the home. Certified installers can determine the necessary framing dimensions for a fireplace and often enlarge the chase dimensions to complement the home's exterior aesthetics. The benefits of a chase enclosure over a masonry chimney include lower construction, materials, and labor costs. In addition to cost savings, chimney chase enclosures offer design advantages, such as more customization options like shelving, recessed bookshelves, television enclosures, and top-level tapering. These designs add significant appeal to the home. A chimney chase can also be used for venting a wood stove chimney through an outside wall and along the side of your home. Starting the chase at ground level is generally the most aesthetically pleasing option.
Before purchasing a chimney pipe, there are several important factors to consider. Firstly, it is crucial to ensure that your installation adheres to local building codes. These codes may include limitations on chimney height or installation format requirements. Secondly, you must determine the amount of venting needed by reviewing a floor plan blueprint. Although blueprints may not be available in every situation, they can aid in calculating the proper amount of venting required. Our Chimney Pipe Buying Guide can provide additional guidance. Thirdly, it is recommended to review all manuals provided by the hearth appliance manufacturer. These manuals often provide various installation scenarios, which can assist in selecting the best venting route for your home. By reviewing this material beforehand, unnecessary expenses can be avoided. This is particularly important for new builds or properties undergoing full renovations. Collaboration between project managers, contractors, and NFI-certified technicians is essential in establishing a list of required venting components.
This section features a list of the top manufacturers and brands in the industry. The list is not in any specific order. Please review the following:
1. DuraVent - Offers a wide range of stove and chimney pipes. Their brands include Duratech, Duraplus, Durablack, and DVL.
2. Selkirk - Manufactures Supervent, Superpro, Metalbest, and Heatfab chimney products.
3. Superior - Provides proprietary chimney systems for Superior wood-burning fireplaces.
4. Majestic - Offers proprietary venting for Majestic wood-burning models.
5. Security Chimneys - Known for the Secure Temp and Secure Black brands of venting pipes.
6. Ventis - Produces a single line of high-quality alternative chimneys at a lower cost. Their systems are similar to Duratech by Duravent.
7. Bernard Dalsin - Offers a specialty line of chimney transition components, connectors, and adapters such as wall thimbles.
8. Napoleon - Sells proprietary venting that works with Napoleon products.
To ensure the safety of your chimney system, it is recommended that you have a certified professional inspect it annually. This will ensure that your venting system is functioning properly. When working with inexperienced installers, it is important to pair them with an experienced expert to ensure that your chase measurements meet your municipality's code. When purchasing a chimney pipe, pay attention to visual signs that indicate malfunctioning in your chimney system, such as smoke flowing back into your living space. Ventilation problems may be caused by back-drafting due to negative air pressure in the room, a firebox that is too small, or blockages within the chimney or chase structure. The firebox should have one square inch of chimney flue for every 10 square inches of the firebox, and the space between the firebox and back of the chimney should not exceed one inch. If you suspect a blockage, look for any obstruction in the pipes, such as insect or animal nests, or residue of soot and solidified gases. Any visible obstruction warrants professional cleaning before using your hearth appliance.
To extend the lifespan of a chimney, most new build installers prefer a chimney chase enclosure over masonry chimneys. The following recommendations apply specifically to this type of chimney structure, but some suggestions may also be relevant to venting pipes extending above a home or business roof. Because climate can affect a chimney chase system, it's crucial to insulate it to fight against the leading cause of chimney fires, creosote buildup. For fireplaces or stoves built outside of a chase, we suggest using a building envelope and a separate enclosure to protect these units from environmental disturbances. However, freestanding stoves don't require enclosures since they sit on a hearth pad or similar protective surface.
To clean a chimney, various supplies are available, and most of them have been explained in detail in this article. However, the most commonly used tool is a chimney brush. Using these products will enable you to maintain your chimney system between inspections. To find out more about general chimney maintenance supplies, click here.