Heating with wood has often been divided into space heating (stoves) and central heating (furnaces and boilers). Wood and pellet stoves typically heat 1,000 to 2,000 square feet of space and even when they are the homes primary heater, there is almost always a boiler or furnace in the basement to supplement the stove, if and when needed. They are best located in the largest and most used space in the house. If they are near a stairwell, the heat can often naturally flow to upstairs rooms. Having your heating appliance in your living space can save up to 20 to 30% of heat that can be lost in leaky ducts in central heating systems.
Pellet furnaces and boilers can operate just like basement fossil fuel furnaces and boilers in that they are controlled by a thermostat and provide heat to the entire house. Modern wood furnaces and boilers can do the same, but they need to be loaded at least once every day. Outdoor wood boilers are whole house heaters that are located in the backyard and the heat is pumped in pipes underground into the house. If you don’t mind losing a lot of efficiency and cleanliness, this allows you to keep your wood outside, and not in the basement.
The modern stove emerged in the early 1990s after the EPA required that all new stoves meet minimum emissions requirement. These new stoves use up to 30 to 40 percent less wood than older models, saving homeowners a lot of work and money, and they emit far less smoke.
Since 2005, wood stoves are again becoming more popular, especially in areas not served by natural gas. If you use an EPA certified stove and burn well seasoned wood (under 20% moisture) wood heat can be an excellent way to affordably heat your home.
The EPA is about to issue new stove regulations so that by 2015, stoves will have to meet stricter standards and loopholes will be removed that allowed some stoves to avoid EPA certification. Most of the very cheap new stoves that sell for $600 or less are uncertified.
Beware of efficiency claims by stove manufacturers. The EPA does not require efficiency testing so there is no requirement to use third party test labs or to use a standard way of measuring efficiency.
Non-catalyric stoves tend to be cheaper and typically cost between $1,000 and $3,000. They tend to burn more quickly and only the larger fireboxes, usually 3 square feet and higher, can hold a fire overnight or through the day without reloading. However, they are more idiot proof than catalytic stoves. Efficiencies tend to range between 65% and 75%, using the higher heating values (HHV). 80% of stoves sold in America are non-catalytic.
Catalytic stoves tend to be more expensive ($2,000 to $3,500) but can hold fire longer and use less wood. They tend to be 75% to 83% efficient (HHV) and are often favored by people who want to use their stove as their primary or sole heat source and who live in colder climates. Catalysts last much longer than the ones in stoves in the 1980s and if seasoned wood is consistently used, can last 7 to 10 years. They also produce less smoke.
The pellet stove was only brought to the market in the 1980s and has been steadily gaining traction since. It’s an American renewable energy technology invention but it’s the European who have adopted and deployed it at a much wider scale. Even Italy, with a fifth the population of the US, usually sells more pellet stoves than the US.
The pellet stove is thought by many to be the way of the future, slowly edging out wood stoves because it blends traditional wood heat with automation and convenience. Pellets for home heating are mainly made from sawdust and wood chips, which are automatically fed into a burn chamber so that the fuel only needs to be loaded into the stove once a day, or less. Pellet stoves excel at providing heat 24 hours a day and enabling homes to drastically minimize or eliminate the use of their fossil fuel boiler or furnace.
A brief shortage of pellets about 5 years ago left uncertainty in minds of some consumers, but pellet production now far exceeds demand. Another pellet shortage is extremely unlikely in the foreseeable future. More and more U.S. pellets are being exported to Europe. Pellets come in 40-pound bags and as of 2013 sell for about $210 to $245 a ton.
Many pellet stoves use thermostats to maintain a constant temperature in the home and can be the sole heat source for most homes that are 2,000 square feet or under. While they often cost about $500 more than comparable wood stoves, their installation costs are often about $500 less.
The biggest downside of pellet stoves is that they have to be cleaned and maintained on a weekly basis by the homeowner during the winter season and they need an annual inspection and cleaning by a professional. Dirty pellet stoves will lose efficiency. They also can break down due to multiple moving parts. Lastly, they require electricity so that in a power outage you will lose heat unless you have a battery back up. Pellet stoves now outsell wood stoves in some parts of the country. About one million pellet stoves are in use today, 2 to 3 times more than residential solar panel installations.
Domestic Pellet Stoves
Domestic pellet stoves are almost always cheaper to buy, and bigger brands are likely to have a better infrastructure for parts and repair. Some domestic models are only 50% to 65% efficient and you can’t rely on manufacturer efficiency claims as they are exaggerated more often than not.
European Pellet Stoves
European pellet stoves are more expensive but tend to be quieter, more efficient, and have a more modern look. Some sold in Europe heat water for space heating and domestic hot water, and can be hooked up to the same tank as solar thermal panels. Efficiency numbers are more likely to be higher and third party verified. (As of 2013, almost all wood and pellet stoves sold in the US advertise efficiency using the lower heating value (LHV), not higher heating (HHV).
Masonry stoves are large heaters built with masonry, ceramic, tile or bricks. What distinguishes a masonry heater is the ability to store the heat from the fire in the masonry thermal mass, and then slowly radiate into your house for the next 12 to 24 hours.
Masonry stoves, also called masonry heaters, are an ancient technology and represent the oldest, high efficiency way of heating with wood. Designs from the 17th century are typically more efficient than most of today’s cast iron and steel wood and pellet stoves.
Masonry stoves are an extremely efficient way to heat your home and are very popular in Europe but remain only a very niche technology in the US. (One theory is that skilled masonry heater builders were always in high demand in Europe and very few emigrated to the US from 1500 to 1900.) Besides the lack of awareness about masonry heaters, the main hindrance of wider deployment is their cost and size. They start around $8,000 for factory built models and often go up to $20,000 for site built ones.
Masonry stoves work by circulating the hot flue exhaust through a series of baffles that heats up the surrounding masonry, and greatly reduces the temperature of the exhaust leaving the chimney. Unlike wood stoves, fires in masonry stoves are burned hot and fast, for more complete combustion.
Factory Built Masonry Heaters
Factory built masonry heaters are growing in popularity as they are less expensive and can be added into nearly any home since they need less, or no structural support added under the floor. Their smaller size does mean that they are likely to hold heat for only 8 to 12 hours, need to be loaded twice a day – and won’t entirely heat a larger home.
Site Built Masonry Heaters
Site built masonry heaters tend to be larger and more expensive as skilled masons need to be on site for 3 to 7 days to build it. They are best in new construction as the heater footprint, like stairways, is a major floor plan design element. Like factory built masonry heaters, they can include baking ovens.
Wood and Pellet Boilers
Indoor wood and pellet boilers are widespread in Europe and are steadily gaining in popularity in the US. Indoor wood boilers have been used in America for many decades, but they tend to be a more basic technology that is not very efficient or clean. Modern, automated pellet boilers (hot water) and furnaces (hot air) using bulk pellets offer homeowners virtually the same convenience as a fossil fuel furnace by feeding fuel automatically from a large storage area. Both New Hampshire and Massachusetts offer generous rebates to install these systems.
Modern indoor wood boilers can have oxygen sensors, microprocessors, and catalyst capabilities. This allows them to achieve very high efficiencies, in the mid 80s, HHV. They need to be loaded once or twice a day and hot water storage tanks ensure that they burn as cleanly and efficiently as possible. Hot water storage allows the full load of fuel to be completely burned, while extra heat is stored in the tank. This prevents the boiler from cycling on and off.
Modern pellet boilers and furnaces also have automated sensors to control combustion, along with automated fuel loading so that the operator may only need to clean out the ash tray once or twice a month. Pellet boilers and furnaces can be loaded daily with 40-pound bags of pellets, just like stoves. They may also have a bulk storage bin that holds several tons of pellets and is only refilled once or twice a winter.
Wood Burning Outdoor Boilers
Outdoor wood boilers, also known as hydronic heaters, are a controversial technology that has spawned thousands of complaints and lawsuits across the country due to excessive smoke. Recently, cleaner outdoor boilers have reached the market, but they can still be problematic in populated areas.
Outdoor wood boilers gained popularity in rural areas where fuel is abundant. They began as a very basic, unregulated technology that was advertised as being an affordable and efficient way to heat your home.
The EPA began a voluntary program in 2007 instead of developing national regulations. Under the voluntary program, companies that meet certain emissions and efficiency standards for at least some of their units can advertise as “EPA Phase II Qualified.” Based on independent third party testing, these boilers are estimated to be 55 to 65% efficient, while the unqualified ones are 35 to 55% efficient. The list of hydronic heaters that qualify for the EPA’s Outdoor Wood-Fired Hydronic Heater program is here. States that have passed regulations to allow only the cleaner, Phase II units to be installed are: Indiana, Maine, Maryland, Massachusetts, New Hampshire, New York, Oregon, Pennsylvania and Vermont. Washington State effectively bans outdoor wood boilers.
The EPA is now in the process of making mandatory regulations, which will likely take effect in 2014 thus requiring all states to only allow the installation of the cleaner, more efficient units.
According to the State of Washington Department of Ecology, “most OWBs employ very primitive combustion technology” and “are designed to burn wood at lower combustion temperatures and generally have shorter stacks, which emit smoke closer to homes and neighborhoods.” Lower combustion temperatures result in less complete combustion, causing increased emissions of particulate matter. OWBs often run on idle periodically to avoid overheating the water, and produce large plumes of opaque smoke as they reheat after a cooling period.
In most parts of the US, you can’t get a truck to come and fill up a pellet bulk storage bin, but in most of New England you can now. 95% of pellet heating in the US is still stoves, which are loaded with 40 pound bags, but these automated boilers are slowly catching on, mostly in Maine, New Hampshire and now Massachusetts. Both NH and MA have incentive programs specifically to help this bulk delivery and technology get off the ground.
Almost all stoves and high efficiency boilers enjoy a modest $300 federal tax credit through the end of 2013. At the state level, as of summer of 2013, four states offer some rebate, tax credit or tax deduction for stoves (ID, MD, MT, OR) and three states have or have had rebates for automated pellet boilers (MA, NH & VT). In addition, there are many local incentives available to upgrade an old, uncertified stove to a newer certified one in parts of CA, OR, WA, AK and other areas.
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For more info about incentives, visit http://www.forgreenheat.org/incentives/federal.html and http://www.dsireusa.org