Wood burning stoves are a money saving appliance in many homes in the United States today. They have proven to be an excellent source of heat as a primary source or as a backup. There have been some changes over the years due to regulation imposed by the US EPA.
Has the EPA banned or made wood burning stoves obsolete or outdated? No, the regulations that have been enacted by the EPA have only made wood stove manufactures produce a cleaner burning version that is sold in the US.
There are many factors that influence the manufactures and production of wood stoves. If you build your own wood stove, the EPA regulations that govern the manufacturers do not apply. There are, however some states and communities that regulate the use and output of wood stoves. That is up to you to verify before installing a stove yourself.
I have researched stove production, EPA regulations and wood burning stove safety in general and the following is what I have gathered.
History of Wood Burners
Burning wood has been the most common form of home heating since cold nights have chilled us (“us”, being humans). Coal became a hotter burning, abundant fuel in the 1800s, but the wood was still abundant and replenishable as a heating fuel.
Generally, wood was burned in an open fireplace for heat and cooking. This made homes hot in the summer and drafty in the winter as most of the heat rose up the chimney. The draft of the chimney pulled air up and out of the heated area actually making the home cooler accept near the fireplace.
Cast iron stoves were produced in the mid-1600s and were little more than a metal box. In 1740, Benjamin Franklin produced the first “Franklin Stove” which is the forerunner to today’s heating stoves.
It was not until the mid-1970s and the “Energy Crisis” (Never miss the opportunity of a good crisis) that several ingenious inventors came up with versions of an “airtight” stove.
This was just a box with legs and a door that sealed the air from entering the stove or at least dramatically reduced the draft of air from rushing up the chimney. Air vents controlled by a closing gear or pipe value could actually cut off the flow of air into the stove.
This allowed wood burning stoves to burn dramatically less wood and at the same time produces more heat for a home. Home built versions were popping up across the US. Several manufacturers began building and selling stoves, and by the early 1980s, the wood stove industry was in full swing.
The operation of a wood burning stove is a simple process. A fire needs three elements to burn. The three elements are heat, fuel, and air. If you remove any one element, the fire goes out. Reduce any one, and the fire burns lower. The goal is to control the heat by using good fuel (wood) and limit the amount of air introduced into the firebox.
The stove firebox needs to be a sealed box (welded), and the doors need to seal to limit the airflow into the stove. Fiberglass rope seals infused with graphite have been developed and are placed between the stove wall and the door to seal the doors safely.
Air vents have been added to the stoves that allow minute adjustments in air flow to dial the temperature up or down just by opening or closing the air flow to the fire.
The air vents were typically on the door or along the side of the stove near the front. They were controlled manually (and still are for most stoves) by turning a valve or sliding a lever. The precise air control is what made these new stoves operate more efficiently.
Some of the stoves included glass in the doors to enjoy the fire. You could actually watch the fire burn hotter as the vents were opened and vice versa.
EPA Regulations
When a new technology takes off and sales increase, the government takes notice. There were several reasons for the intervention of the EPA into the wood stove manufacturing industry. By reducing the air input to the firebox in the new stoves, the output of the stoves had larger amounts of particulate matter that polluted the air.
The output of the stoves had changed due to the reduced air flow into the firebox, and the increased use of firewood as a fuel also caused some users to burn wood that was not seasoned properly. Unseasoned wood also causes additional PM or particulate matter to be expelled from the stove.
There were more people using wood burning stoves, and this caused a firewood shortage, so less drying time for the available wood in the mid-1980s.
Wood as a fuel is one of the few renewable sources of fuel we have. More trees can be planted and will replace the trees we burn today.
In the US 1.6 billion trees are intentionally planted each year. This does not include the effect of natural reforestation which is when trees drop a seed that grows without human help.
There are more trees being planted every year than are harvested. Together through planting and natural re-forestation, the US exceeds the use of trees by 3.3%. This means through natural re-growth and by planting, every year there are more trees than are used for firewood and industry.
Back to actual regulations on wood burning stoves, in 1988 the first regulations were imposed on manufacturers of wood stoves. In 1998 the regulations were tightened, and additional guidelines were included.
In 2015 the EPA added even stricter limits on the amount of PM that was allowed to be exhausted from a wood burning stove. As it stands now, in 2020 the strictest standards yet will be introduced to the wood stove industry.
As of 2019, there are over 100 wood burning stove models that meet the 2015 standard. The guidelines for PM output regulate that no more than 4.5 grams per hour be expelled from a stove. The guidelines set to be enforced in 2020 for PM output are 2.0 grams per hour based on testing with cord wood.
How Manufacturers Meet the Regulations
Two different versions of wood burning systems have been developed by manufacturers to meet the EPA standards. Catalytic stoves and non-catalytic.
A catalytic stove uses a catalytic device much like a vehicle catalytic converter to re-burn the smoke and lower the PM output through this process.
If you have ever climbed under a vehicle after (or while), it has been running a few minutes, you know the intense heat that is generated from a catalytic converter. The catalytic device in a stove requires the wood burner to be brought up to temperature before it is engaged.
This involves opening a by-pass damper on the stove while lighting it then closing it once the stove has reached the required temperature, somewhere between 350-500 degrees depending on the brand and model. Once the by-pass damper is closed, all the smoke passes through the catalytic converter. This heated catalytic device then re-burns the smoke which reduces the PM that exits the stove out through the chimney.
The non-catalytic stove uses a secondary baffle above the firebox to re-burn the smoke. Above this baffle, pre-heated air is introduced to the smoke stimulating the secondary burn. It has the same effect as the catalytic stove without the catalytic device.
Both of these types of stove do the job. They reduce the amount of PM that exits the stove while burning wood for heat. There are pros and cons of each system.
The Good the Bad and the Ugly
None of us want to pollute the air intentionally. If there is a method or product that pollutes less we should use it if it is reasonable. The newer versions of the wood burning stove will absolutely pollute the air less than the older versions built before 1988.
Another positive aspect of the newer stove innovations is the reduction in creosote output of the stove. Creosote is a by-product of burning wood, especially at lower temperatures. Creosote particles collect on the inside of the stove’s surface and on the inside of the chimney.
This tar-like substance is called creosote and is a fire hazard especially in the chimney if ignited by higher temperatures or flames; a chimney fire could damage a chimney. Reducing the creosote is a fantastic benefit of the newer stoves.
However, with all this great new wood stove engineering, we do have to give something up!
First, the cost of a new wood burning stove has more than tripled (even adjusted for inflation).
Second, the temperature must be hotter to activate a catalytic device or add the pre-heated air to the non-catalytic stove. This makes using a wood stove in early fall, and late spring, when low stove temperatures are required, very difficult if not impossible with some models.
Third, the catalytic device requires regular cleaning and in some models replacement after 3-5 years of use. This may come as a shock at $125 – $450 depending on the model and size.
Defining PM and its Affects
Smoke from any wood fire is a mixture of gasses and fine particles (PM). The list of gasses includes benzene, formaldehyde, acroline, and polycyclic aromatic hydrocarbons in trace amounts. These are the fine particles that are carried in the smoke and can cause health risks.
The finest particles called PM2.5 are 2.5 micrometers and smaller. This is not detectable by the human eye and is also carried in smoke.
These particles are a contributing factor to lung disease, asthma, and COPD. Limiting your exposure to any smoke is recommended if you have any of these health issues.
Safety
There are several safety issues when you own or install a wood burning stove. The primary concern is safety from a fire in the home, and there are additional concerns regarding the fumes emitted from the smoke.
Since this article deals primarily with the EPA and its regulations, let’s look at the fumes exhausted in the smoke first, which is what we want the smoke to do, exit the home through the chimney and dissipate in the great outdoors. If the system is working correctly, then there is no issue with the gasses and PM that is emitted.
However, if the chimney becomes clogged either slowing the smoke flow or completely blocking the exit of the smoke, these gasses have to go somewhere. They will back up into the home.
Checking that the chimney has no leaks and is free of creosote and animal nests is extremely important. The chimney is the exit pathway for the harmful gasses and must be fully free of debris and open to allow the continuous draw of heat and smoke up the chimney.
Keeping the chimney clean is also important when it comes to fire safety. Most home fires that are linked to a wood burning system are a result of a clogged or dirty (creosote) chimney.
Inspecting and cleaning the chimney is the single most important maintenance item on the wood burning system checklist. More issues are a result of chimneys that are not properly maintained than any other part of the wood burning system. A few simple checks and precautions can prevent these issues.
Chimneys
There are three types of chimney systems used for fireplaces and wood burning stoves. Each has pros and cons and needs to be evaluated to meet your particular need and price range.
- Masonry
- Triple Wall
- Double Wall
Masonry or brick and mortar are what you will typically think of when you think “chimney”. They look great and work well but require the most maintenance and attention.
A masonry chimney needs to be cleaned and inspected regularly. The flue liner can crack and leak under stress of extreme heat or if water (freezing and thawing) damages it. I recommend a professional cleaning and inspection annually at a minimum.
A triple wall chimney by name sounds like the best type of chimney since it has 3 walls. They do work well but do not provide as much protection from heat as the double wall chimney. The triple wall chimney uses the air space in the middle as the insulation from the heat going up the chimney.
The best type of chimney for wood burning stoves is the double wall chimney. There are two walls of stainless steel and high-temperature insulation in between. Typically a double wall chimney has the highest heat rating, up to 2400 degrees F.
The high-temperature insulation will not only protect the walls of a home on the outer surface of the chimney but will also provide insulation to the inner wall of the chimney from the cold outside air. This helps to prevent creosote from building up on the inner wall of the chimney.
There are two things you can do to reduce creosote build-up in your stove and in the chimney. Burning the best hardwoods and making sure the wood you burn has been properly seasoned is number one.
The Best Firewood
Hardwoods provide more heat than softwoods! The BTU output per cord is much higher in most hardwoods than in medium or softwoods. Finding a supply of quality hardwood for burning is not only vital to heating and keeping your home warm throughout the winter, hardwood, when burning hotter, will burn cleaner.
The hotter burning fire from the hardwood will also keep your stove and chimney cleaner. Depending on what is available to you, oak, osage orange, hickory, and ash, if it has not been eradicated by the emerald ash borer, make the best firewood. These all burn hot and will assist in keeping the stove and chimney free of creosote and other deposits.
Season Your Firewood
The final matter when it comes to firewood is burning wood that has been properly seasoned, or dried. Burning firewood that has too high moisture content can cause multiple issues within your system.
The proper moisture content for wood to burn in a wood heat system is between 15% – 20% moisture content. Burning wood dried to this range will allow your system to operate at peak efficiency and will permit the smoke and particles in it to exit the system properly.
Wood that has higher moisture content will burn inefficiently. The moisture must be removed from the wood to burn. This means a great deal of the heat produced is used to heat up the moisture and send it out of the log as steam. Some of the steam will condense on the walls of the stove and the walls of the chimney pipe. This will become creosote and is a chimney fire hazard.
To properly season the firewood, it should be cut, split, and stacked off the ground so each row of wood will receive sun and wind to dry. This will take six to nine months at a minimum. My personal recommendation is a full twelve months for the wood to reach the target moisture content range all the way to the center.
The wood should be uncovered while drying. To accelerate the process, placing the wood in a woodshed will shorten the drying time. A wood shed is an open, covered structure, with walls that let the air through. Typically, they have three walls with siding that is spaced 2-3 inches apart allowing the air to flow through. A simple roof that sheds the rainwater will speed the drying process.
Conclusion
The EPA has left its mark on the wood burning industry. The regulations have changed the construction of the wood stove, and for the most part, for the better. As in any industry, change is inevitable. This change was imposed by regulations and has made an impact over the past 30 years.
Innovation has also come in the form of new types of stoves. Outdoor wood stove, called hydronic heaters (because they heat water piped into the home) and pellet burners have taken hold and will be around for years to come.
The pellet burners generally meet even the 2020 EPA regulations mostly because they burn manufactured wood pellets that have set moisture content. As long as the pellets are manufactured, pellet burners will be a viable wood stove alternative.
As long as lumber harvesting corporations continue to re-plant as they use their resource, wood for stoves will also be readily available.
Regulations will be imposed by our government and innovations will continue to find a method that burns the wood efficiently and within the guidelines.
Additional Questions
How much wood does a wood burner use in a season? A typical wood burning stove will use 3-4 cords of wood in a season. There is a wide range of factors that affect this. To read more on this subject see my article, How Much Wood Will a Wood Burning Stove Burn in a Season?
Is a wood burner more efficient than a pellet burner? It depends on your definition of efficiency, cost or BTU output. On BTU output a pellet stove is more efficient. On the cost of fuel, a wood burner is less expensive to operate. If you would like to read more on the subject, see my article, Wood Burner vs. Pellet Burner, Efficiency and Cost.