More Information Your Old Wood Stove's Dirty Little Secret brochure

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Today’s wood stove models feature improved safety and efficiency--they produce almost no smoke, minimal ash, and require less firewood. While older uncertified stoves release 15 to 30 grams of smoke per hour, new EPA-certified stoves produce no more than 4.5 grams per hour. Look for the EPA certification label on the back of the stove, or check the current list of EPA-certified wood stoves. Also check for safety labelling by the Underwriters' Laboratories of Canada (ULC) or another testing and certification body.

Emission Limits for Wood Stoves

The internal design of wood stoves has changed entirely since the EPA issued standards of performance for new wood stoves in 1988. EPA's mandatory smoke emission limit for wood stoves is now 4.5 grams of smoke per hour (g/h) under Step 1 of the revised standards of performance for wood burning room heaters; Step 2 will take effect on May 15, 2020, when the standard will be lowered to 2.0 g/h. Heaters using the optional cord wood test method must meet a standard of 2.5 g/h. A voluntary hangtag marks units that meet these standards before the May 2020 date. Stove manufacturers have improved their combustion technologies over the years, and now some newer stoves have certified emissions in the 1 to 4 g/h range. When comparing models, look for the EPA white label on the stove - a lower g/h rating means a cleaner, more efficient wood stove. Learn more about wood stove regulations.

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Types of Wood Stoves

Types of Stoves Cross section of a non-catalytic stove showing combustion air/exhaust flow patterns, large baffle and high level combustion air supply. Cross section of a catalytic stove showing combustion air/exhaust flow patterns, the catalytic element, and the bypass damper. The two general approaches to meeting the EPA smoke emission limits are non-catalytic and catalytic combustion. Both approaches have proved effective, but there are performance differences. Although most of the stoves on the market are non-catalytic, some of the more popular high-end stoves use catalytic combustion. Because they are slightly more complicated to operate, catalytic stoves are suited to people who like technology and are prepared to maintain the stove properly so it continues to operate at peak performance.

Non-catalytic stoves

Non-catalytic stoves do not use a catalyst, but have three internal characteristics that create a good environment for complete combustion. These are firebox insulation, a large baffle to produce a longer, hotter gas flow path, and pre-heated combustion air introduced through small holes above the fuel in the firebox. The baffle and some other internal parts of a non-catalytic stove will need replacement from time to time as they deteriorate with the high heat of efficient combustion.

Catalytic stoves

In catalytic combustion, the smoky exhaust is passed through a coated ceramic honeycomb inside the stove where the smoke gases and particles ignite and burn. Catalytic stoves are capable of producing a long, even heat output.

All catalytic stoves have a lever-operated catalyst bypass damper which is opened for starting and reloading. The catalytic honeycomb degrades over time and must be replaced, but its durability is largely in the hands of the stove user. The catalyst can last more than six seasons if the stove is used properly; but if the stove is over-fired, inappropriate fuel (like garbage and treated wood) is burned, and if regular cleaning and maintenance are not done, the catalyst may break down in as little as 2 years. (EPA note: Garbage should never be burned in a wood stove or fireplace.)

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Finding the Right Size and Model

Video Guides Introduction to Wood Stoves - HPBA A Quick Guide on How to Select a New Stove for Home Heat - Washington State Department of Ecology

When choosing a wood stove, consider the size of the space you'll be heating. Wood stoves come in different sizes, and can be sized to heat a single room or an entire home.

Small stoves are suitable for heating a family room or a seasonal cottage. In larger homes with older central furnaces, you can use a small stove for "zone heating" a specific area of your home (family or living room). This can reduce fuel consumption, conserve energy and save you money while maintaining comfort.

Medium stoves are suitable for heating small houses, medium-sized energy-efficient houses, and cottages used in winter.

Large stoves are suitable for larger, open plan houses or older, leakier houses in colder climate zones.

EPA maintains a current list of EPA-certified wood stoves. However, it's best to talk with experienced hearth product retailers who know the performance characteristics of the products they sell. When visiting local retailers, take along a floor plan of your home; knowledgeable retailers can help you find a wood stove, fireplace insert, or other hearth product that is well suited to the space you want to heat.

If you're trying to determine if your current wood stove is EPA certified under EPA regulations, look for the permanent metal EPA certification label on the back of the stove, or you can check to see if your model is listed in the current list of EPA-certified wood stoves.

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