How To Vent A Wood Stove Or Wood Fireplace

When considering the installation of a wood-burning fireplace or stove in your home, it is important not to overlook the crucial component of venting. Adequate venting is essential for optimal stove function and efficiency. However, with various venting options available, it may be challenging to determine where to start.

Manufacturers usually limit the venting systems that their appliances can handle, which simplifies the selection process. However, there are still key factors to take into account to ensure optimal performance. This guide outlines the different components required for proper venting of a wood-burning appliance.

The categories of venting systems for wood-burning fireplaces and wood stoves may appear to serve the same purpose, but they differ significantly. Venting for wood-burning appliances is divided into two main categories.

The air-cooled chimney system is the first type of chimney system. It uses air for cooling, as its name suggests. The space between the chimney walls allows for the free flow of outside air. Most systems use two walls, but there are also three-walled systems. These chimney systems are usually large because air does not insulate as well as solid material. The design of these systems allows for at least two inches of air space between each wall layer. Most air-cooled chimney systems have free-floating chimney walls, which means they can expand independently and be assembled in individual sections. Many prefabricated decorative wood-burning fireplaces use this type of system. Almost all manufacturers offer proprietary venting systems specific to these appliances. Therefore, it is impossible to substitute other brands of venting as doing so would create unsafe venting and deviation from standing codes.

Insulated chimneys are a type of venting system that utilizes a layer of solid insulation between the inner and outer walls of the chimney. This insulation can be made of ceramic blanket, mineral wool, or fiberglass. Three-wall chimneys combine air-cooled and insulating components, with solid insulation placed between the inner and center walls. The space between the center and outer walls allows for air circulation, which provides additional cooling. Unlike air-cooled systems, insulated chimneys are solid constructions that prevent the inner and outer walls from separating. This is achieved through the use of welded or riveted caps at the end of each chimney section or riveted braces between the pipe walls. Insulated chimneys are necessary for high-temperature wood-burning fireplaces and stoves to maintain safe temperatures for surrounding combustible materials. Third-party companies manufacture various insulated chimney systems, which are rated for specific appliances. While many brands can fit a single appliance, the differences between brands and material grades are discussed in detail below.

Despite their differences, various chimney systems share common features. For instance, they both use a stainless steel inner flue wall that prevents damage from corrosive flue gases and allows for offsets to navigate around obstacles. They also permit the use of fire stops to pass through each combustible floor. Finally, each system has its own set of support and termination components that work together to create a weather-tight seal above the roof.

Determining the necessary venting for your appliance is crucial before making a purchase. It is important to first identify any unique circumstances you may have, followed by confirming the venting options approved by your local code. The owner's manual provided by manufacturers offers a detailed list of potential venting scenarios, which can take up to a third of the manual's text. It can be frustrating to discover that your desired hearth is not permitted in your area, but there may be alternative options available. Conducting thorough research beforehand can prevent costly mistakes and the inconvenience of return and restocking fees. This guide aims to demystify venting measurements and clearances to ensure a seamless installation process. When constructing a new home, we suggest working closely with your builder and an NFI certified technician to develop a comprehensive list of necessary venting components. Access to your home's blueprints is an excellent starting point for planning, enabling you to coordinate everything from venting height to offset dimensions. Furthermore, the technician can compile a list of components specific to your application.

Chase Or No Chase!
When installing venting systems for wood-burning units, they can be routed through the ceiling if enclosed properly within the home's envelope. Alternatively, a purpose-built chimney envelope or chase secured to the exterior of the home can also be used. Chimney chases are a popular choice because they contain the entire chimney system without sacrificing space and conceal venting pipes passing through upper levels of a multistory home. Although more expensive, a chase is the most effective option if conserving floor space is a priority. The base of the chase must accommodate the framing dimensions of the fireplace, and smaller dimensions for a rough frame of a chimney chase are about two square feet. Manufacturers specify clearance requirements in inches, which is important to consider when framing. It is recommended to work with a seasoned installer to follow height and code regulations, and to insulate the chase before enclosing to prevent large temperature differences and poor appliance performance.

In certain instances, a chimney or oven may not be constructed within a chase. Instead, it is located within its own enclosure inside a building envelope. Freestanding stoves may even be placed on a specially constructed hearth pad or surface. In such cases, it is necessary to consider how the venting system will be installed from the appliance and throughout the house. If it is not feasible to allocate space for the vent run within the home, the vent may be angled towards the exterior wall and fed into a cantilevered chimney that is designed to hold the vent pipe itself. If the vent remains inside the home, a framed enclosure may be used to hide the system, which can be finished with drywall or another material. Ideally, the vent pipe should be routed to a room corner or closet to avoid being visible.

 

When selecting the vent route and appliance, it's important to check your venting components list. For wood-burning fireplaces with a single venting system, the choice is straightforward. However, some brands offer several systems for their products, making it a bit more complicated. For appliances with multiple brand options, it can be challenging to know which components to choose. Factors to consider include pricing, availability, material quality, and your specific installation. Pricing and material quality are closely related, with venting systems made of lower quality stainless steel, such as 430 grade, being cheaper but also less durable. The choice of materials often depends on the fuel type and personal preference, with wood fuels being less corrosive than coal or fuel oils. Some customers prefer to use a better system for added peace of mind. If you're unsure, our NFI certified technicians are available to help you find the best venting system for your budget.

When installing appliances that use air-cooled or solid insulated chimneys, it's important to evaluate your installation plan. Air-cooled systems don't work well in cold climates, so enclosing as much of the vent pipe as possible is recommended if it's your only option. Using a solid pack chimney is the best option for proper venting if it's permitted. Once you've chosen a venting brand, note the measurements of the venting system. Measuring the distance from the top of the "as installed" appliance flue collar to the "as built" height of the chimney chase is straightforward for a vent system routed through a chimney with no offsets. Add any height needed above the chimney chase for a storm collar and chimney cap, typically between 8-12 inches. A combination of different length pipes is usually needed for proper venting, and it's important to consider the number of inches each section adds to avoid running too short. Manufacturers provide an offset chart for installations that need offsets or a length of chimney to extend through a pitched roof. They specify the number of elbow sets or pipe sections that can be added between them, with most offering fifteen or thirty-degree elbow sets. The maximum allowable offset by code in the United States is thirty degrees, and manufacturers also specify how many offsets each vent run can have, including how much offset the total pipe length can be.

In order to determine the required amount of chimney pipe, one must first calculate the offsets and locate the point where the roof will be penetrated. This will enable the application of the 3-2-10 rule, essential for proper venting and code compliance. The 3-2-10 rule aims to avoid poor appliance performance, soot staining, or damage to the adjacent structure of your home, that may result from a chimney that is too short.
The numbers in the rule have specific meanings:
- 10: This number sets a radius of 10 feet around the chimney pipe to ensure that objects within this radius meet clearance requirements. The steeper the roof, the more pipe will be needed. If any part of the home within this radius is taller than the chimney, that must also be taken into account.
- 2: After establishing the 10-foot radius, two more feet of pipe must be added before terminating it. This ensures that the chimney avoids drafting issues caused by the house stack effect, which refers to a ventilated part of the home being taller than the chimney.
- 3: This rule applies to all situations and means that any pipe penetrating a roof must be three feet above the roof line on the up-slope side of the penetration. If the roof is steep or there is a nearby obstruction, the chimney will require more length above the roof to comply with the code. Solid-pack chimneys can be left exposed and braced, but air-cooled chimneys should be enclosed any length of pipe five feet above the roof to avoid poor performance from excessive chimney cooling, particularly in colder climates.

To install a fireplace, after planning and ordering venting components, begin the installation process. It's important to note that this is a general guide and specific situations may require additional components or bracing.

Proper alignment is necessary for fireplaces installed inside the home with roof flashing. Before securing the appliance, make sure the vent collar and venting path are aligned correctly. Changing the vent run during construction can cause an offset between the two. If an offset is required between the fireplace and the ceiling, install it as high as possible in the run. This allows flue gases to gain more velocity before having to negotiate the offset. To begin installation, attach the first flue section to the vent collar on the fireplace. For air-cooled chimneys, attach the inner section first followed by the outer section. This type of chimney has a hem and lance system that audibly snaps when secured. In contrast, solid-pack chimneys typically have an anchor plate that secures the first section of pipe. Twist-lock systems rotate into position and lock when fully installed. Assemble each pipe section and secure the outer wall using three #10, 3/4 self-tapping stainless steel sheet metal screws equidistant around the pipe perimeter. Maintain clearances to combustibles during assembly and brace vertical venting every 5 to 6 feet using the manufacturer's provided perforated strapping or wall brackets.

To ensure proper installation, follow the manufacturer's instructions and install a firestop or radiation shield where the pipe run meets the ceiling. Nail a piece of OSB across the opening and cut a hole to the size of the firestop. Secure the firestop in place and continue the assembly and bracing sequence while passing through the attic or second floor. Use an attic insulation shield in the attic space, which is especially important for homes with blown insulation. Obtain the attic insulation shield from the chimney system manufacturer or box the chimney into an enclosure, ensuring the chimney pipe maintains proper clearances. When passing through the roof, use a flashing that matches the roof pitch and nail it in place after laying down the tar paper or weather membrane, before installing the roofing material. For shingles, ensure the trailing edge of the flashing base sits on top and that the upper and adjacent courses of the shingles overlap under the edge of the flashing base. For metal or tile roofs, follow the manufacturer's instructions, which typically involve covering the entire base of the flashing, cutting a hole for the flashing cone to project out, and sealing the roof to the base of the cone with roofing sealant. After installing the flashing, continue assembling the chimney pipe, routing it through the flashing and meeting the 10-3-2 height requirements. Finally, install a storm collar around the top of the flashing cone.

A storm collar and chimney cap are essential components for proper chimney installation. The storm collar is a thin steel or aluminum strip that wraps around the pipe and redirects water towards the flashing cone. It can be secured with bendable tabs or fasteners, but it's important to apply flashing sealant to the pipe's outer wall before installing the collar. Once the sealant is in place, assemble the storm collar around the pipe and slide it down into the sealant. Check to ensure that there are no gaps between the collar and the pipe and add more sealant if necessary. After the storm collar is securely in place, it's time to install the chimney cap. For solid insulated chimneys, the cap can usually be twisted into position. However, air-insulated chimneys require brackets to be screwed into the chimney system, since the cap doesn't have lances. Once the cap is installed, the system is finished and ready for testing.

The installation process for the interior pipe with chimney chase is identical to that of the attic. Upon reaching the attic, the builder will construct a chimney chase that should extend from the roof decking to the ceiling joists to provide support. For the pipe passing into the base of the chase, an insulation shield may be utilized, or the chase may be enclosed after the pipe is installed. The pipe should be run the same way as the previous sections, throughout the chase. It's possible that the chase may not fit each new section of pipe with the other assembled pipe, depending on its size. In such cases, the remaining length of pipe from the top of the chase to the end of the last installed pipe should be measured. This length should then be assembled on the roof and installed from the top of the chase down. Each pipe section should be secured with fasteners before feeding the length into the chase. Once this procedure is complete, the process should be repeated to assemble to the storm collar and cap.

Chase pans or chase flashing are commonly found at the top of chimneys. They are typically made of 18 to 22-gauge galvanized steel and cut to fit the outer dimensions of the chase. The ideal chase pan should have a 90-degree drip edge, be at least 2 inches deep, and fit over the chase's edge. Larger pans should have cross bracing or in-bracing to support the pan. The pan's hole should be about 1/2 inch larger than the chimney pipe's outer wall, with a formed or welded collar standing at least 3/4 of an inch tall to prevent water from rolling back into the chase. Chase pans can be obtained from local sheet metal fabricators and roofing suppliers, as many manufacturers do not supply them due to the variety of sizes needed.

For a full exterior chimney chase installation, the process is simpler compared to an interior installation. However, you still need to construct the chase framing, but you should keep the exterior sheathing off for easier access during the installation. It is recommended to install at least one firestop halfway up the chase to comply with local codes. You can use OSB, plywood, or whatever material is acceptable in your area. The manufacturer's metal firestop must be installed in the center of the material. Depending on the footage, local codes may require additional firestops, so it's important to plan accordingly. Once the fireplace is in place, assemble and fasten the chimney sections together. The installation should stop once the last section protrudes from the top of the chase, allowing you to complete the exterior of the chase. After the exterior is complete, install the chase pan and cap, and place the storm collar in place.

This is a comprehensive guide on how to install wood stove pipe through a wall. When installing a wood-burning stove, stovepipe is required, which differs from chimney systems. Stovepipes, also known as chimney connectors, come in single or double walls and the installation process depends on whether it is vertical, horizontal, or a combination of both. Single-wall stovepipes are usually made of 22 or 24 gauge steel, while black galvanized steel pipes are double-walled with an inner pipe made of either 430-grade steel or 304 stainless steel. The outer wall is constructed from 22 or 24-gauge black-painted galvanized steel. Stovepipes connect the stove to the first wall or ceiling of the vent run. They are designed to be aesthetically pleasing while also allowing some heat reclamation from the venting run. The configuration of the vent run is determined by the stove's installation.

For stoves that have a complete vertical run, the venting requirements are the same as those for a fireplace. The house blueprints should be used to determine the length of the run that needs to be installed for any modifications to the structure. If the installation is being done in an existing home, the ceiling joist and roof rafter locations should be surveyed. Ideally, the vent run should be positioned to avoid these framing members. However, sometimes it may be necessary to cut and box in a ceiling joist or roof rafter to accommodate the vent pipe. Only individuals who are qualified and knowledgeable should undertake this part of the project. Once the stove location has been decided, it is important to determine if a single or double-wall pipe is needed. Single-wall pipe does not last as long as the stainless interior of a double wall pipe, but they do cost less. The amount of clearance space needed should also be considered. Single-wall stovepipe requires 18 inches whereas double walled only need 6 inches. With a corner or alcove installation, space is limited, so clearances may call for a double-wall pipe.

Stovepipes often have telescoping sections that can cover varying distances between the stove and ceiling. Slip connectors are also available in single-wall systems. These connectors are short pieces of pipe that have a smooth end, allowing them to fit into a section of pipe before connecting to the chimney system. It is important to measure the distance between the vent collar on the stove and the ceiling before purchasing a stovepipe, taking into consideration the length added from the chimney support box or ceiling support. Built-in fireplaces and wood stoves require solid-insulated chimneys due to higher flue gas temperatures. The vent pipe remains the same for both high-efficiency fireplaces and stoves, but the associated components may differ.

Ceiling support boxes and collars are necessary for venting stoves. These parts are used to transition from the stove pipe in the room to the chimney pipe above the ceiling, and they bear the vertical weight of the chimney components. Ceiling support collars are designed for flat ceiling installation, so they're shorter than ceiling support boxes. Ceiling support boxes come in varying lengths and project downward into the room. Support boxes can be used on a flat ceiling, but they're mainly used to offer an extension through a vaulted ceiling. The length of the support box needed depends on the steepness of the vaulted ceiling to maintain clearances. To install the ceiling support box or collar, determine the center location above the stove vent collar with a plumb bob. Then, cut a hole in the ceiling that fits the fixture's size. Most ceiling support boxes and collars take chimney pipe clearances into account. After cutting the hole, brace all sides of the fixture with 2x4s or similar lumber and screw the ceiling support in place. Once the ceiling support is in place and plumb, assemble the stovepipe. Modern stovepipe systems use smooth ends, and the sections fit over each other with self-tapping sheet metal screws to hold them together.

Vent collars come in different sizes depending on the brand, therefore stove pipe adapters are provided by manufacturers to begin the pipe run. These adapters are typically 3 to 4 inches tall with a tapered end that fits into the stove collar. The opposite end is smooth and connects with the first section of stove pipe. For optimal installation of stovepipe, we suggest using as many rigid sections as possible and avoiding the use of multiple telescoping sections as they are prone to scratching and do not seal well. Begin installation by fitting the first rigid section and continue until there is only a gap left between the stovepipe and support box. Collapse the telescoping section slightly and slide it down to fit between the last pipe section and the ceiling support. Connect this pipe to the stovepipe section below and screw the bottom sections together. Extend the upper section into position against the ceiling support box and use screws to keep the telescoping components in place, but note that many manufacturers do not permit fastening the stovepipe to the support box. To complete the stovepipe run, installation of the chimney is similar to a fireplace, except for the initial chimney section that drops into the support box. This section can originate from either the attic or the second floor and must be twisted into position. After running the chimney pipe through the support box, install an attic insulation shield or radiation shield around it. The rest of the installation process is the same.

This article provides a comprehensive guide on how to vent your wood-burning fireplace or stove horizontally to an outside wall when vertical venting is not feasible due to the home's structure. The process involves transitioning from stove pipe to chimney pipe when passing through the wall and using a wall thimble instead of a ceiling support box. The horizontal vent run is similar to the vertical vent run except for the return to a vertical chimney secured to the outside of the home.

Two-piece adjustable adapters known as wall thimbles are designed with a collar to adapt between two different pipe types while accommodating various wall thicknesses. Specific guidelines must be followed when using horizontal venting to ensure proper venting. The process begins with a vertical run of stovepipe before making a 90-degree turn towards the wall, with most manufacturers suggesting at least 12 inches of vertical run from the stove for flue gases to gain upward momentum before encountering any restrictions. The horizontal section must have a 1/4 inch rise per foot of run to prevent flue gases from stagnating in the vent run. A horizontal run of no longer than 50% of the total vertical run is typical, depending on the manufacturer's specifications. Wall thimbles are used instead of ceiling support boxes for horizontal installations, so it is essential to locate the ideal position before installing, which may require cutting and boxing a wall stud to allow space for mounting the thimble. The manufacturer instructions cover this further. Consider the vertical height of the stovepipe from the top of the stove, and don't forget to account for the height added by the 90-degree elbow when determining the position of the horizontal sections. Measure up from the floor and mark the center point of the thimble, then cut out the space needed to install the thimble. To install the stovepipe, begin with the rigid sections and work from the stove to the wall while installing the slip connector or telescoping section last. Fasten each section of stovepipe with self-tapping screws, then connect it to the wall thimble. The chimney installation process differs for external installation, requiring a short section of the horizontal chimney to attach to the outer side of the wall thimble, with the length depending on the wall thickness. The horizontal run should extend far enough to allow proper clearance of the vertical section as it travels against the side of the home.

To transition from a horizontal chimney run to a vertical one, install a chimney tee which consists of three components: a horizontal leg to accommodate the horizontal chimney, a vertical leg for the vertical chimney, and a plugged bottom leg to prevent any leaks. To sweep the vertical section of the chimney, simply remove the plug. A tee support bracket is required for the tee and can be provided by the manufacturer or made by the homeowner. Assemble the chimney with the tee attached and resting on the bracket. To ensure stability, place vertical supports using wall straps or similar metal bands every 5 feet. This guide offers complete instructions for venting your wood-burning fireplace or stove.

Homes often have eaves or enclosed soffits that extend beyond the outer wall. Depending on the depth of the eave, there are several methods for dealing with this. Shallow eaves of no more than 2 or 3 inches can use offsets, which allow the chimney to make a slight jog around the eaves without altering the structure of the home. Homes with deeper eaves, between 6 and 10 inches, have a couple of other options. The first option is to notch the eave, leaving an open cutout for the chimney pipe to pass. This can be finished with fascia boards and a rain diverter to prevent water from pouring into the notch. A second option is to build the chimney into the eave, using metal flashing to enclose it. Of course, clearances to the wooden structure still need to be maintained. This method is ideal due to the support supplied to the chimney. For homes with deep eaves of 10 to 36 inches, the chimney must pass through the structure and be finished with flashing on the roof to ensure appropriate support and prevent the need to cut an excessively large notch. A metal flashing can also be added around the chimney as it passes through the eave's underside. For all applications, it is crucial to adhere to the 10-3-2 rule once the chimney is above the roofline to determine its appropriate height. Topping out the chimney with a cap is the same as with other installations, but a storm collar is not necessary if there is no roof flashing.

For any pipes installed above a roof without support from a chimney chase, it is essential to have appropriate support above the roof line. Unsupported pipes extending no more than five feet are permissible. High winds can cause unsupported pipes to bend or become damaged. Several manufacturers provide rigid dual leg brackets that can be used to attach pipes to the roof. Alternatively, cables can be used to secure the pipe to anchor points.

To ensure proper installation, it is necessary to test the venting for draw and leakage. This can be done by lighting a small, kindling-based fire in the appliance and inspecting accessible areas of the venting for smoke leaks and condensation drips. Any leaks should be addressed by repositioning the stovepipe or chimney pipe and adding more fasteners if necessary. If the chimney does not draw well, check the horizontal run and make sure it does not exceed the allowed ratio, as well as ensuring the pipe meets height requirements and adheres to the 10-3-2 rule. If the vent system is too short, add pipe sections to correct for the house stack effect.

Achieving proper venting for your wood-burning appliance may appear daunting initially. However, this guide can assist you in accomplishing the task with ease and confidence. With a bit of persistence and patience, you can ensure that your wood-burning appliance is vented efficiently. If you have any additional questions regarding venting, chases, or other concerns related to fireplaces, we are here to provide answers.