Homeowner’s Guide to Wood Heating
Wood burning equipment that meets modern environmental standards is up to 30 percent more efficient and pollutes up to 90 percent less than older equipment. Especially in the Maritimes, where fuel is readily available at low cost, wood heating can be an economical and renewable option for many homes.
The United States Environmental Protection Agency (EPA) has established regulations pertaining to emission levels for wood-burning appliances. Reference to EPA standards may appear in Canadian Federal or Provincial energy efficiency regulations. Furthermore, Efficiency Nova Scotia also has minimum standards that wood/pellet burning equipment must meet in order to qualify for a rebate.
Improved combustion chamber design is the key to better performance in today’s stoves and fireplace inserts. As a
result of their increased efficiency, EPA-certified stoves can burn up to 30 percent less wood than older stoves
that do not meet EPA standards. Properly maintained wood pellet stoves burn cleanly and efficiently over a wide range of heat outputs. Pellet stoves need electricity to operate as the fuel is automatically fed into the stove’s combustion chamber by a small motorized auger.
Wood Furnaces and Boilers
Wood furnaces and boilers can comfortably heat an entire house from a central location, using air ducts or hot
water pipes to distribute the heat throughout the home. Although the equipment may be able to provide sufficient
heat for the entire home, an automated backup heating system, such as electric heat, is usually required to satisfy
Wood-fired central heating systems may be a poor choice in homes with low heating needs as their high heat output may cause overheating, inefficient operation, and creosote buildup. They can be dangerous if overheating occurs as a result of a fan failure or a power outage. To combat this, safety features are included in their design, but careful sizing, installation, operation, and maintenance are the best defense against fire or smoke damage. Wood
furnaces cannot be connected to most existing oil fired furnace systems unless duct work clearances from combustible surfaces are substantially increased. Central wood pellet furnaces and boilers can provide automated operation for several days at a time. Larger hoppers can either be filled via a bulk delivery or by manually adding bags of pellets.
Canadian manufacturers are at the forefront of today’s improved wood stove technology. Advanced combustion stove systems use carefully designed fireboxes to optimize combustion. Improved firebox insulation, preheating of combustion air, and internal baffles are all features that lead to increased performance.
For maximum efficiency, make sure your wood-burning equipment is the right size. Large stoves often overheat
today’s well insulated homes. A small stove that operates at high efficiency for the majority of the heating season is a much better choice than a high output stove that overheats your home on all but the few coldest winter nights. A smaller stove generally burns cleaner and uses less fuel because of its higher operating temperatures.
Your wood stove should be located in the space you wish to heat, yet many stoves end up in the basement even when the goal is to heat the main level. This causes poor heat distribution, excessive wood use and greater heat loss out of the basement, especially if it is poorly insulated. Due to negative pressure, basement stoves are also more likely to backdraft than stoves located on the main level. Locate your stove where you spend most of your time.
Wood-burning equipment must be carefully installed to be safe and efficient. It is highly recommended that you have your stove professionally installed by a technician certified by the WETT (Wood Energy Technical Training) program, Canada’s only system for training and recognizing competence in the field of residential wood burning. There are hundreds of WETT certified installers, technicians, chimney sweeps, sales advisors, and inspectors in Atlantic Canada. If in doubt, ask for proof of current certification. Your installation must also conform to local building and fire safety codes, as well as CSA safety standards. Talk to your fire department or building inspector before installation. Notify your household insurer in order to maintain coverage and avoid disputes after installation. Manufacturer’s instructions on clearances and connections must be followed. The chimney system must be sized and approved for use with your stove. Wood stoves depend on the draft generated by a hot chimney to safely exhaust combustion gases. Because interior chimneys are always warm, draft is better and condensation or creosote problems are much less likely to occur than with exterior chimneys. Any heat lost by an internal chimney remains in the home. Insulated chimneys also help to maintain good draft. Older masonry chimneys may require a metal liner.
Careful control of the air supply determines how completely the fuel is burned. To avoid starving the appliance of air, keep draft controls open as much as possible. When you start a fire or add wood to it, the fresh fuel requires much more air for the first 10 to 15 minutes. Once the wood is well charred, the amount of air required drops off. Loosely stacked pieces burn faster since combustion air can reach all pieces at once.
Control heat output by the amount of fuel supplied. One cord of seasoned hardwood (moisture content under 18%) burnt in an efficient appliance should produce the same amount of heat as 500 litres of oil or 4400 kilowatt-hours of electricity.
To monitor your wood stove’s performance, watch the flames. Is the fire burning brightly? As your wood decomposes, it vaporizes into smoke – a cloud of combustible gases and tar droplets. When operated efficiently, a fire should burn hot enough to produce bright lively flames. Dull, steady flames, on the other hand, are a sign of oxygen starvation and incomplete combustion.
Older, oversized, low-quality, or homemade woodburning equipment can produce large quantities of noxious smoke. Excessive, highly visible, or smelly smoke is an indication of unburnt fuel from incomplete combustion. It is usually caused by restricting the air supply to the fire. Incomplete combustion increases fuel cost, fuel use, creosote buildup, and the risk of chimney fire and poisonous gas leakage. Some smoke may be visible when you first light the fire, but for the remainder of the burn, the flue gases should be almost invisible.
If you use your wood stove overnight, ample ventilation and properly loaded fuel is necessary to avoid a smouldering fire. To build a long-lasting fire, rake the coals towards the air inlet and place larger pieces of wood in the firebox behind the coals. Place logs in a crosswise fashion to allow air flow between the pieces of wood.
Open the air inlets fully for 15 to 30 minutes, depending on the size of the load and its moisture content. When
the outer pieces have acquired a thick layer of charcoal, reduce the air supply slightly to the desired level. The
charcoal insulates the rest of the wood and slows down the release of combustible gases. This allows you to turn
down the air control and still maintain a clean-burning fire.
Chimneys and flue pipes must be inspected regularly for creosote buildup and other unsafe conditions. Chimneys
should be cleaned at least once a year. Cleaning may be needed every few weeks if green wood is burned, the stove is oversized, long slow burns are common, or if the flue pipe between stove and chimney is too long (it must not exceed 3 m/10 ft. in length). For new installations, inspect chimneys and piping every month until you’ve determined how often your system needs cleaning.
Plastics, painted or treated wood, and manufactured wood products should not be burned in a residential stove or fireplace. They may emit toxic chemicals and may damage catalytic combustors.
Never use freshly cut or green wood; it contains 35 to 50 percent water by weight and burns inefficiently. You can
reduce your wood consumption by 25 percent simply through allowing it to dry, or “seasoning” it, before you burn it. Wood should be seasoned to a moisture content below 20 percent to avoid wasting much of its heating value driving off excess moisture. Buy your wood in the spring and shelter it from the weather for at least six months before the heating season.
The size of the wood you use is also important: smaller pieces of wood burn cleaner because they have more surface area exposed to the flame. Wood should be split to a maximum thickness of 10-15 cm (4-6 in.), depending on stove size, and 10 cm (4 in.) shorter than your firebox.
The best way to store wood for drying is cut to length, split and stacked. Keep your wood off the ground and
let air flow under the stack by laying down poles or 2x4s first. Leave space for air to circulate between the pieces. Use plywood, metal or plastic to keep the rain and snow off your wood.
Do not store wood inside your house as the moisture leaving the wood will increase the relative humidity inside
the home. Higher relative humidity levels increase the likelihood of mold and mildew growth.
Wood pellets are made from waste wood that has been formed under high pressure into small cylindrical pellets.
These pellets are homogeneous, dry, and easy to burn. They are sold in easy-to-handle bags, so fuel storage is
clean. Fuel hoppers usually hold at least a full day’s worth of pellets. Pellets are automatically fed to the combustion zone by a small motorized auger.
Pellet-burning appliances include space heaters, fireplaces, furnaces, and barbecues. Unlike conventional
wood-burning equipment that relies on natural draft, wood-pellet appliances have two small blowers; one supplies the combustion air needed for a clean, efficient burn and the other delivers heated air to the home.
During a power failure, pellet stoves can’t function unless provided with a battery backup. Combustion gases produced by wood-pellet heaters contain virtually no creosote. They’re also cool enough to be safely vented through a side wall, although vertical venting is recommended to provide sufficient draft to empty the combustion area of smoke in the event of an exhaust fan failure or power outage.
Wood smoke should never be noticeable in your home. To avoid back-drafting (smoke coming into your home) as a result of negative pressure, locate your stove on your home’s main level and fully open the draft control shortly before opening the door for refuelling. Poor wood-burning practices create smoke, which contains compounds that can cause health problems. Some of these include carbon monoxide, hydrocarbons, nitrogen oxides and a range of organic chemicals that are hazardous to human health. Harmful smoke particles are small enough to seep around closed doors and windows or to pass through ventilation system intake filters.
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