(also called stove pipe, smoke pipe, chimney connector, etc.)

The rules provided here are based on the CSA installation code used in Canada. For the exact rules in your area, check with a local wood heat retailer, chimney sweep or building inspector.

1. Maximum overall length of straight pipe: 3 m (10 ft.)
2. The assembly should be as short and direct as possible between the stove and chimney. The use of two 45 degree elbows is often preferable to a single 90 degree elbow because less turbulence is created in the exhaust flow and they result in less horizontal run.
3. Maximum number of 90-degree elbows: 2. Maximum unsupported horizontal length: 1 m (3 feet).
4. Galvanized flue pipes must not be used because the coatings vaporize at high temperatures and release dangerous gases. Use black painted flue pipes.
5. 6-, 7-, and 8-inch diameter flue pipes must be at least 24 gauge in thickness.
6. Flue pipe joints should overlap 30 mm (1 1/4 in.)
7. Each joint in the assembly must be fastened with at least three screws.
8. The assembly must have allowance for expansion: elbows in assemblies allow for expansion; straight assemblies should include an inspection wrap with one end unfastened, or a telescopic section.
9. Minimum upward slope towards the chimney: 20 mm/m (1/4 in/ft.).
10. One end of the assembly must be securely fastened to the flue collar with 3 sheet metal screws and the other end securely fastened to the chimney.
11. There must be provision for cleaning of the pipes, either through a clean out or by removal of the pipe assembly. Removal of the assembly should not require that the stove be moved.
12. The crimped ends (male) of the sections must be oriented towards the appliance so that falling dust and condensation stay inside the pipe.
13. A flue pipe must never pass through a combustible floor or ceiling or through an attic, roof space, closet or concealed space.
14. Minimum clearance from combustible material: 450 mm (18 in.). The minimum clearance may be reduced by 50 percent to 225 mm (9 in.) if suitable shielding is installed either on the pipe or on the combustible surface.

A straight up single wall flue pipe assembly.The ideal flue pipe assembly is one that rises straight up from the appliance flue collar and directly into the chimney with no elbows. The system at the right is single wall pipe with an inspection wrap (pipe coupler) to allow it to be assembled and disassembled without moving the stove.

A straight flue pipe assembly offers the least restriction to gas flow and results in stronger draft. Straight assemblies also need less maintenance because there are no corners for creosote deposits to accumulate.

A perfectly straight flue pipe assembly is another good reason to install chimneys up through the warm space of the house, instead of out and up an outside wall.

Certified double-wall flue pipe systems are also available. These systems are tested to determine the minimum clearance at which they can be installed. The clearance information is found on the labels attached to the pipe and in the manufacturer's installation instructions. The rules for their installation may differ from the rules for single-wall flue pipes.

A straight up double wall flue pipe assembly. This one is the sealed type.The minimum installation clearances for certified double-wall flue pipes are much less than those for single-wall pipes. Also, the maximum length of a double-wall flue pipe assembly may be greater than is permitted for a single-wall pipe.

There are two general types of double-wall flue pipes: sealed and vented. A sealed double-wall flue pipe is effective at retaining the heat in the flue gases because the air space between the inner liner and outer shell acts as an insulator.

A sealed double-wall pipe is a good choice to maximize draft and minimize creosote deposits. Use sealed double-wall pipes if the assembly must be long or if the appliance is expected to produce low flue gas temperatures. The system to the left uses a sealed double wall telescopic length between the stove and chimney.

A vented double-wall pipe allows cooling air to pass between the inner and outer layers. Where the flue pipe assembly is short and straight, a vented double-wall pipe can be acceptable. However, vented pipe is not a good choice for longer flue pipe assemblies or for appliances that are expected to produce low flue gas temperatures.

JG

How to determine the right clearance and how to reduce it safely

A stove that has been tested and certified as meeting a safety standard has a label on the back showing how much clearance is needed from combustible material like walls and furniture. This information is also found in the manufacturer's installation instructions. If there is no label, the stove is not certified.    

Almost all new wood stoves currently offered for sale have been safety certified and most insurance companies will only accept certified appliances. Stoves that are not tested and certified include used or antique stoves or stoves that have been built by small, informal welding shops.

It is a good idea to avoid uncertified stoves for serious heating because their safety and efficiency are likely to be inferior and many insurance companies refuse to cover houses containing them. Also, because they have not been tested, their performance is unknown, so the minimum required clearances to combustible material are very large: 1200 mm (48 in.) for radiant stoves and 900 mm (36 in.) for stoves surrounded by jackets behind which convection air can flow.

Clearances for an uncertified stove

The clearance for an uncertified radiant stove is 1200 mm (48 in.) and for a stove with a sheet metal jacket or casing the clearance is 900 mm (36 in.). The clearances are large because they apply to all shapes, sizes and designs of stoves that have not been tested to determine the actual clearances.

Clearances for uncertified stoves

* Shielding consists of protection such as external jacketing or metal heat shield attached to the sides and rear of the appliance and spaced out at least 50 mm (2 in.) by non-combustible spacers, with provision for air circulation at bottom and top. Clearances are measured from the outer surface of the appliance to the combustible material.

Reducing Minimum Clearances Safely

We all want our wood stove installation to take up as little floor space as possible, so the reduction of minimum clearances using special shields is common. The clearances for both certified and uncertified stoves can be reduced safely using the rules set out below. The common feature of the clearance reduction rules is the air space behind the shield material. This space sets up a convection flow of air as the stove is operating and prevents most of the stove's heat from reaching the wall behind. The percentage indicated in the table is the amount that the minimum clearance may be reduced with the particular shield system listed. Both wall and ceiling clearances may be reduced using shields.

A variety of materials can be used for clearance-reducing shields, from simple sheet metal to more decorative shields using brick, stone slices or ceramic tiles. Shields must be permanently mounted to walls. Free-standing, folding panels should not be used as shields.

Reducing Clearances With Shielding

Shield Construction Rules

1. Minimum space between shield and combustibles: 21 mm (7/8 in.).
2. Minimum clearance along the bottom of shield: 25 mm (1 in.).
3. Maximum clearance along the bottom of shield: 75 mm (3 in.).
4. Minimum clearance along the top of shield at ceiling: 75 mm (3 in.).
5. Shield extension beyond each side of appliance: 450 mm (18 in.).
6. Shield extension above appliance: 500 mm (20 in.).
7. Edge clearance for ceiling shields: 75 mm (3 in.).
8. Adhesives used in shield construction must not ignite or lose adhesive qualities at temperatures likely to be encountered.
9. Mounting hardware must allow full vertical ventilation.
10. Mounting hardware must not be located closer than 200 mm (8 in.) from the vertical centre line of the appliance.
11. Mounting hardware which extends from the shield surface into combustibles may be used only at the lateral extremities of the shield.

Details of a wall shield By allowing air to flow between the shield and the combustible surface, a wall shielding assembly can be used to safely reduce minimum clearances. The shield is required to extend at least 500 mm (20 in.) above the top of the appliance and 450 mm (18 in.) beyond each edge of the appliance.Commercial shields are also available for the reduction of minimum clearances. These shields are subjected to a series of tests to determine how effectively they can reduce clearances. They are certified and carry a label which confirms that they have met the tests and provides information on clearance reduction details. Some of these commercial shields are designed so that they can be attached directly to combustible walls without the need for an air space.

The first step in reducing clearances is to determine the minimum clearance, either from the appliance label or from the table of clearances for uncertified appliances. Then, calculate the permissible clearance reduction for the type of shield you plan to use from the table on clearance reduction. The channel spacers shown are the most effective type to use because they give good support to the shield and do not transmit heat through the mounting hardware to the combustible wall. Metal wall strapping, available from most building supply stores, is made of light steel channels that work well as shield spacers. Note that the bottom of the channel is notched to allow cool air to enter. The shield must extend 450 mm (18 in.) beyond each edge of the appliance and 500 mm (20 in.) above the top of the appliance.

Protection for the Floor

Wood stoves that are certified as meeting the safety test standard will not overheat a combustible floor. During testing, the floor temperature is checked and must not exceed safe limits.

Although the floor will not overheat due to stove operation, the floor must be protected from live embers that might fall from the stove during fire tending or ash removal. The floor pad must be made of a durable, noncombustible material, such as sheet metal, grouted ceramic tile, or mortared brick. Floor pads must normally extend not less than 450 mm (18 in.) in front of the loading door and 200 mm (8 in.) beyond the other sides and back. Floor pads must not be installed on carpet unless the pad is structurally supported so that it does not move or distort.

Floor pad size The floor pad protects flooring from hot embers that might fall from the appliance during fuel loading or servicing. The pad should extend at least 200 mm (8 in.) beyond the sides and rear and 450 mm (18 in.) in front of the loading door. The floor pad must be a continuous, non-combustible surface. The floor pad must not rest on the carpet unless it is strong enough to resist bending or cracking. The best floor pads are laid on the sub-floor so that their finished level is flush to the floor, so there is no edge to trip on.

Uncertified stoves have not passed safety tests, so heat from the bottom may overheat floors. The rules for floor protection for uncertified appliances are complicated, with several different types depending on how high the legs support the stove from the floor.

If you are installing an uncertified appliance, you should contact a qualified professional for details.

JG

Thirty-five years ago people flooded into wood stove stores to buy anything they could use as a hedge against high oil prices and threats of shortages. The 1970s and early 1980s energy crisis rush back to wood heat after decades of decline led to thousands of tragic house fires.

Today, householders still return to wood heat to shield their families from unpredictable oil and gas prices and electrical supply failures caused by the violent storms that seem to be more frequent.  In 1999 many others installed wood stoves just in case the Y2K problem had posed a real threat. And the collective shock induced by events of September 11, 2001 seems to have created another surge of wood stove sales.  For supporters of wood heating, the trend back to wood heat is both encouraging and a little worrying. While we like to see more people rediscovering the comfort and security of wood heating, we don't want to see a repeat of the fires that destroyed so many homes. And there is no excuse for taking a risk this time. Here's why.

Then:

No one knew much about wood heat safety a few decades ago. Safety codes were crude and based on decades-old information. Product safety certification and professional training did not exist at the time, so retailers, installers and even building inspectors were just floundering around doing the best they could with limited information. Homeowners thought that wood heat safety was just a matter of 'common sense', so they installed stoves themselves without much guidance. The results were bad — lots of house fires and lots of insurance claims. To this day the insurance industry has a rather negative attitude about wood heating, having been badly burned by all the losses.

Now:

Starting in the early 1980s when it became apparent that we had a serious safety problem with wood heating, government and industry rushed to develop safety standards for products. These led to much better stoves, fireplaces and furnaces that were accompanied by reliable installation instructions giving safe installation clearances. The wood heat industry developed professional training programs to educate their members on how to find and use the safety rules. Today the industry is much more sophisticated. Wood stoves are now certified for low emissions as well as safety. Installers and chimney sweeps have become professionally certified by attending courses and passing examinations.
If you think wood heat safety is just common sense, think again!

Don't put your family's safety at risk. Research wood heat safety requirements by following these links:

• A comprehensive Canadian government booklet on all matters of wood heat.

Get professional advice and if possible, have a professional installer put the stove and chimney in for you. Here is how to identify qualified personnel.

• In Canada, look for retailers, installers and chimney sweeps who are WETT certified under the Wood Energy Technical Training program.
• In the United States, look for retailers and installers certified under the National Fireplace Institute training programs.
• Look for certified sweeps at the Chimney Safety Institute of America site

Get it right so you don't have to worry

A safe woodburning system consists of:

• a safety certified stove, fireplace or furnace
• the right type of chimney for the appliance
• a system design that avoids safety compromises
• reliable advice on safe installation, or preferably, installation by a qualified professional

Before you make decisions about your new hearth, visit at least two specialty stove and fireplace retail stores and ask a lot of questions.  Only then will you begin to get a balanced view of how to match your needs and objectives with a system that will achieve them.

The choices you make now will pay off later in comfort and piece of mind.