How To Prepare Firewood for Your Outdoor Wood Boiler

Properly preparing wood can make a world of difference in how effectively your wood boiler operates. So, if you are interested in understanding more about how to prepare firewood for your outdoor wood boiler or indoor wood boiler to help maintain a comfortable temperature inside your house year-round, you aren’t alone.

Many people wonder why their wood-burning outdoor furnace or indoor furnace doesn’t heat their home appropriately, even when it has plenty of wood (especially in colder weather). To help keep this common problem from happening to you, read on to discover more about what type of firewood is best to get. Additionally, you’ll learn how to prepare and store it correctly, and you will also receive useful tips from Alternative Heating & Supplies on how to ensure that your indoor or outdoor wood boiler does its job right, regardless of the weather.

What Type of Wood is Best to Burn in a Wood Boiler?

All wood will burn, but is tossing in just any kind of firewood into your outside wood boilers the best move to make? On a day with mild weather, your outdoor wood boiler will probably be able to keep up regardless of what kind of wood you are using, but you may run into trouble on chillier days if you always abide by this practice. So, let’s go into more detail about the various types of firewood, what makes them different, and which is best to burn in your furnace.

  • Hard Woods vs. Soft Woods: Trees can either be classified as hard or soft. Softwoods catch fire quickly and have more BTU’s per pound then hardwood and are excellent at getting your fire started. However, they do deposit a lot of creosote, don’t create much of a coal bed and burn up fast. So, if you plan on using softwoods for more than just a fire starter, buildup often becomes an issue, and the wood may burn too quickly. On the other hand, when your firewood comes from hardwood trees, it tends to burn longer, but you should plan on seasoning and preparing your firewood before using it in your wood boiler. Mixing Soft and hard wood is another great option.
  • Greenwood vs. Seasoned Wood: Wood that has been recently cut down and had less than a month to dry is referred to as greenwood. Seasoned wood is split, stored, and allowed to dry, so it’s moisture content decreases. Seasoned wood is much more efficient and will produce longer-lasting heat for your furnace
  • Types of Firewood: There are various kinds of wood that burn well in wood boilers. You can still use some greenwood and softwood like pine, hemlock, and spruce. However, if you use these types as firewood, we recommend that you mix in seasoned hardwood to build up a good coal bed. Popular hardwood choices include oak, cherry, ash, mulberry, and hackberry.

Preparing Wood for Your Outdoor Wood Boiler

When you want to cut and prepare firewood yourself for use in your outdoor wood boiler, you need to have a well thought out plan to maximize your furnace’s efficiency as well as reduce its creosote production. Below is some advice for cutting and splitting logs to use as firewood.

  • Cutting Stacking Logs: When you cut your wood, aim to make them roughly the same size if possible (around 20 inches is a popular length for most furnaces). If they are too long, it can be difficult for one person to carry them.
  • Making a Good Cut: For thinner wood use a sturdy sawbuck that has cross pieces at least 20 inches apart with plenty of clearance for your saw. First, cut down on your log until it starts to pinch, then do an up cut to sever the two pieces. Electric 14-inch chain saws are a popular choice because they are affordable and easily turn on and off. Another option is to use a gas-powered saw if you want to cut your logs on the ground. With this tool, you roll your logs a half turn for your final cut.
  • Splitting Your Wood: To split your wood, you need a maul and splitting block or a gas powered splitter. Your wood’s cross-section dimensions should be a little smaller than the smallest part of your boiler’s door. Remember, if you don’t split your wood, you are not allowing its moisture to leave. When you have too much moisture inside your firewood, it takes 30% more energy for your boiler heat exchanger to convert your wood into heat since it must vaporize the moisture before it can burn the wood.

Tips and Tricks to Ensure Good Wood Burning

At Alternate Heating & Supplies, we have years of experience with how to prepare wood for burning. Here are a couple of our favorite tips and tricks that will hopefully make your life a little easier. These best practices can simplify and take the guesswork out of preparing your firewood so that it burns well in your indoor or outdoor wood burners and keep your home continuously heated to your desired temperature.

  • How to Stack Your Wood: Don’t make your woodpiles too tight or deep as this can prohibit airflow. Instead, plan on leaving at least six inches in between each pile for space. Additionally, there is no need to stack your firewood in tall mounds that look perfect. Although that method may look impressive, it can restrict the airflow that is needed to get rid of moisture.


    Loosely stacked, smaller woodpiles tend to dry better. When your piles have open-air gaps, most of the water from heavy rains gets splashed away. It’s also a good idea to put your firewood mounds on pallets. This way, you get airflow underneath your pile to optimize the airflow, sun, and moisture.

    You also must be careful if you plan to stack your wood in the shade. During the summer, your firewood needs exposure to the sun to help pull out its moisture.

  • How to Cover Your Wood: When you tarp your wood, don’t cover your pile completely. If you cover it entirely, you allow moisture to remain inside, and it can’t evaporate the way it should. This practice can lead to mold buildup and cause your firewood to turn black.


    Instead, try making a tent shape over your woodpile, so that water can drip off and fall to the ground. When you use this tarping method, you’ll notice that even in summertime, it still feels moist inside your ‘tent.’ This wetness is a good sign since it means that your wood is continuing to get rid of its moisture. Likewise, you’ll also find that if you have seasoned wood, moisture will accumulate at the top of your ‘tent,’ then it will drop down to the ground.

    Another idea to consider is making a shed for your firewood instead of tarping. This type of shelter provides excellent airflow, and you don’t have to worry about rain and snow landing on your wood. However, instead of a regular roof, construct a greenhouse roof made from two-ply sheets of clear plastic. Your shed will get very hot in the summer, so you’ll see moisture dripping from your greenhouse roof if its doors are closed. Therefore, if you chose this method to store your wood, try leaving the door of your shed open as much as possible so that the moisture blows away.

What to Know When Gathering Firewood

If you are interested in gathering firewood yourself, you need to know what time of year is best to cut down trees. In the fall, trees lose moisture, which is why they drop their leaves. They are starting the process of beginning to prepare for the low-moisture season of winter. Whereas, in spring and summer, trees have the most water flow, and their trunks are comprised of 40 to 50% water.

Therefore, if you cut down a tree to use for firewood, the ideal time is when it is losing its leaves in fall. Once cut, lay it down, and if there are still green leaves on it, let it lay there until the remaining leaves pull out moisture from the rest of the tree.

You can still cut down trees in spring and summertime, but it may be more of a challenge to season your firewood. Once cut, you will have to let them lay for three to four weeks until their leaves are dry. This allows the leaves to pull moister out of the tree. Then, you can cut and split your trees, which will help reduce their moisture levels.

How to Keep Your Wood Boiler Heating Properly

If you experience problems with keeping your home heated, there is a good test to help you figure out if there is something wrong with your outdoor wood boiler, or if the wood you are using is what’s causing issues. Purchase a few bundles of firewood from your local store. Then, put them into your outdoor furnace where they will burn hot and fast. If your wood boiler can get to your desired temperature with this wood, you’ll have confirmation that your furnace is working well, and your problem is the wood itself.

If this is the case, you probably have too much moisture in your firewood, which prohibits your water to air heat exchanger from working the way it should. In other words, your wood boiler is unable to keep up with demand because the wood you are putting in it is not burning at the right speed. Therefore, it is essential to take care of your wood and season it right before using it to ensure that it burns efficiently.

Now that you understand more about firewood and how to prepare it correctly, you’ll want to be sure that you use it in a high-quality store-bought or homemade outdoor wood boiler. Alternate Heating & Supplies has all the outdoor wood furnace parts and indoor wood stove parts and supplies that you need. So, whether you are searching for a circulation pump, a wood stove blower motor, aquastats, or any other indoor and outdoor boiler parts, we have you covered. Check out our wide selection of wood stove parts and supplies online, and be sure to contact us with any questions. For more information be sure to visit Alternative Heating & Supplies YouTube Channel, and subscribe to our channel!