How Much Heat is Wasted Up the Chimney of a Wood Burning Stove?
How efficient is my wood stove
If you have a wood burning stove, you might wonder how efficient it is at heating your home and how much heat is lost up the chimney. Here we will explore these questions and explain why some heat loss is necessary for a safe and clean operation of your stove.
What is Efficiency?
The efficiency of a wood burning stove is an indicator of how much fuel will be used and how much “wasted”. For example, a stove rated at 80% efficiency will lose 20% of the heat in the combustion process. This counts for little when it comes to how “cleanly” the stove burns its fuel.
The efficiency of a wood burning stove is measured by comparing the heat output to the heat input. The heat output is the amount of heat that is transferred to the room or the heating system. The heat input is the amount of heat that is contained in the firewood.
There are different types of efficiencies often calculated for wood burning appliances. Combustion efficiency represents a calculated measurement (in percent) of how well the wood burning device is converting the wood into usable heat. It does not reflect how much of the usable heat produced is transferred to the home.
Overall efficiency is the percentage of heat that is transferred to the space to be heated when a load of fuel (e.g., firewood, pellets) is burned. Actual efficiency will vary depending on factors such as wood moisture, appliance operation and installation (e.g., outside piping, chimney height). Overall efficiency is a better measure than combustion efficiency of the amount of heat that is delivered to the home.
How Efficient are Wood Burning Stoves?
While open fireplaces can be as little as 10 or 20% efficient at burning firewood, the majority of wood stoves can be found with efficiency ratings of between 60 and 80%, with some models even reaching into the 90’s for efficiency.
A good quality stove should be around 80% efficient. This means 80% of the heat that is being produced from the stove is being used to heat the room. The remaining 20% is lost up the chimney or through other parts of the stove.
However, not all models on the market have an efficiency rating listed. The EPA requires manufacturers of all wood heating appliances subject to the 2020 air emission rules to test and report overall efficiency as part of the EPA-certification process. EPA has a list of certified wood heaters that include the overall efficiency by manufacturer and model.
If you encounter an unspecified efficiency, you can check to see if the overall efficiency number for the specific device is included on EPA’s certified wood stove database . If not, you may want to contact the manufacturer or ask your retailer to provide you with documentation of overall efficiency.
Why is Some Heat Loss Necessary?
You might think that losing 20% or more of your heat up the chimney is a waste, but it is actually necessary for a safe and clean operation of your stove. Here are some reasons why:
A certain amount of heat loss creates a draft that draws fresh air into the stove and pushes smoke and gases out of the chimney. This prevents back-drafts, creosote buildup and carbon monoxide poisoning.
A certain amount of heat loss keeps the chimney warm enough to prevent condensation and corrosion. A cold chimney can also cause smoke to cool down and form creosote, which can ignite and cause a chimney fire.
A certain amount of heat loss reduces emissions and improves air quality. A hotter fire burns more completely and produces less smoke and pollutants. The EPA-certified stoves have lower emissions than older models because they have improved combustion technology and secondary air supply.
How to Improve Efficiency and Reduce Heat Loss?
While some heat loss is inevitable, there are some ways you can improve your stove’s efficiency and reduce unnecessary heat loss. Here are some tips:
Choose an EPA-certified stove that meets your heating needs and has a high overall efficiency rating.
Use dry, seasoned firewood that has been split and stored properly for at least six months. Wet or green wood burns poorly and produces more smoke and creosote.
Follow the manufacturer’s instructions for loading, operating and maintaining your stove. Use only approved fuels and avoid overloading or under-loading your stove.
Install your stove correctly with adequate clearance, insulation and ventilation. Use a properly sized chimney that meets local codes and standards.
Clean your stove and chimney regularly to remove ash, soot and creosote. Hire a professional chimney sweep at least once a year or more often if you use your stove frequently.
Conclusion
Wood burning stoves are efficient and eco-friendly ways to heat your home, but they also lose some heat up the chimney
This heat loss is necessary for a safe and clean operation of your stove, but it can be minimized by choosing the right stove, using the right fuel and following the best practices. By doing so, you can enjoy the warmth and comfort of your stove without wasting too much energy or money