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Technology

Updated: November 2019

Wood Stoves

The modern wood stove emerged in the early 1990s after the EPA required that almost all new stoves meet minimum emission requirements. These new stoves can use up to 30 to 40 percent less wood than older models, saving homeowners a lot of work and money, and they can emit far less smoke when they are used properly.

Traditionally people think of two types of wood stoves: catalytic and non-catalytic. But today, there are also hybrid stoves and automated stoves. These two new categories offer great economic and environmental benefits to consumers – and their neighbors. All four types are discussed below in detail.

The EPA issued new wood heater (including wood stoves) regulations in the spring of 2015. As of May 15, 2020, all wood and pellet stoves will have to meet stricter emissions standards of 2 grams an hour (or 2.5 grams an hour if tested with cordwood). Previous exemptions that allowed some pellet and wood stoves to be manufactured and sold without EPA certification are gone. Key provisions that will impact consumers can be found here.

The EPA requires stoves tested after May 15, 2015 to report verified efficiency numbers that can be found on the list of EPA certified stoves. Make sure to check for efficiencies on the EPA site as efficiencies on manufacture websites and literature are often exaggerated.

Non-catalytic stoves
Non-catalytic stoves are the most common and almost all of them introduce pre-heated air into the back and/or top of the stove to trigger and secondary burn of the smoke. They typically cost between $1,000 and $3,000 and tend to burn through fuel more quickly than catalytic or hybrid stoves. Only the larger fireboxes, usually 2.5 cubic feet and larger, can consistently hold a fire overnight or through the day without reloading. They are more idiot-proof than catalytic stoves. Efficiencies tend to range between 65% and 75% using the higher heating values (HHV).
Catalytic stoves
Catalytic stoves tend to be more expensive ($2,000 to $3,500) but can hold a fire longer and are more efficient, using less wood for the same heat compared to non-catalytic stoves. They tend to be 75%- 83% efficient (HHV) and are often favored by people who live in colder climates or want to use their stove as their primary or sole heat source. Catalysts last much longer than the ones in stoves in the 1980s. If seasoned wood is consistently used, they can last 7 to 10 years. They also produce less smoke but require more care and attention by the consumer. There is a longstanding and vigorous debate about the pros and cons of cat vs. non-cat stoves.
Hybrid
Hybrid stoves use both non-catalytic and catalytic technology to achieve maximum efficiency and cleanliness. Many manufacturers make them now and they can offer the best of both technologies. They typically run in the $2,500-$4,000 range and achieve 78-85% efficiency. Hybrid stoves are now one of the technology subtypes listed in the search function of the new EPA stove database. The Alliance for Green Heat recommends this new breed of stove for those who want a cleaner, higher efficiency appliance.
Automated
The newest type of stove on the market is the automated or ‘smart’ stove that use sensors and computer chips to adjust airflow. Other models that help ensure a cleaner burn in the hands of the average consumer use a single burn rate or a bi-metallic dampers. Automated stoves enable the consumer to "load and leave," allowing the stove to maximize efficiency and emissions reductions on its own. Automated stoves are an emerging class that is more well-known in Europe and just starting to enter the US market. The Danish company Hwam was one of the very first with a fully automated model, though its current offerings may not be as automated. and MF Fire, a Maryland based company launched an automated stove model in 2016. The Canadian manufacturer SBI won an award at the 4th Wood Stove Design Challenge for their progress toward an automated stove. In the single burn rate category, the RSF Delta Fusion is an excellent example that meets the 2020 EPA emission standards at 1.3 gram an hour.
 
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