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Efficient Heating with Outdoor Wood Boilers in 2024

Outdoor wood boilers are actually a very simple design. This makes them both easy to use and maintain but the biggest draw of owning a wood-burning boiler is its efficiency and reliance on renewable energy. Efficiency might not be the first word that comes to mind when thinking about large, outdoor wood-burning furnaces but that couldn’t be further from the truth. There has been much advancement in the field of outdoor boilers that just might make you consider installing one for your heating needs.

Let’s take a look at how these units work, what maintenance is needed and what exactly makes them such a desirable, energy efficient option.

How an Outdoor Wood Boiler Works for Efficient Heating

The main portion of the boiler is located entirely outside of your home. Unlike a traditional woodstove that creates wood smoke, ash and dirt in your indoor living space, an outdoor boiler keeps all of those contaminants outside and away from your family. Another benefit of this outdoor system is that it eliminates the need to haul wood into your home. You can store all your firewood outside in a convenient location near the unit. You can restock your outdoor boiler in less than five minutes with this setup!

Outdoor boilers do not carry the same risks of fire and carbon monoxide poisoning that is traditionally associated with indoor wood-burning heat sources. Everything potentially hazardous is outdoors and away from your family. 

The boiler itself works in a similar fashion to a woodstove; only, instead of the fire heating the ambient air around its source, the firebox heats a tank of water that surrounds it. This tank of water is known as a water jacket. This hot water is then used to heat your home via heavily-insulated water lines that are buried under the ground leading from the boiler to the building it is connected to. The boiler utilizes a pump to circulate the water; bringing hot water in and cold water back out to the boiler to be reheated by the firebox and circulated once again.

These boilers don’t have to stand alone! They certainly can function on their own but they can be tied into your existing heating system, whatever it may be. If you already have baseboard heat, the attachment is fairly straightforward and they can also be interfaced with your hot water heater, providing you with a way to heat your home’s water entirely with renewable energy!

If you have a forced-air system, a heat exchanger will need to be installed but this is a relatively simple process. The heat exchanger transfers the heat created from the hot water into warm air that can be circulated throughout your home by use of your existing furnace fan. Take a look at the FAQ section below for a little more detail on interfacing with a forced-air heating system.

These wood boilers can be used to heat multiple buildings with a single unit. This is ideal for farms and countryside dwellers who need to be able to heat several outbuildings throughout the winter. Using a single, wood-burning unit can simplify operation and maintenance for the property owner in these types of scenarios.

Another advantage of outdoor wood-burning boilers is their ability to provide in-floor radiant heating. This alone makes them an increasingly popular choice for homes as well as garages and other buildings.

Easy Maintenance for an Outdoor Wood Boiler

As an outdoor boiler owner, there are two big things you need to do to keep your wood boiler heating efficiently. The first is restocking the wood and the other is cleaning the ash.

Modern wood boilers use a thermostat mounted to the wall just like a forced-air furnace would. These thermostats are digital and created for ease of use. 

As for restocking the boiler with wood, we recommend twice per day. While your wood boiler is perfectly capable of heating your building if you only add wood once every 24 hours, it is far more efficient to add wood twice a day. A smaller fire will burn hotter and cleaner than a smoldering longer between burn cycles. If you only stock the boiler once a day, the fire will be smoldering by the time you go to add wood. You’ll lose a little bit of efficiency but we know that sometimes people have busy schedules and unexpected events that might take them away from home. While it is ideal to add wood every 12 hours, you don’t always have to.

The only other task needed to take care of your wood boiler during the heating season is to empty the ash weekly. We recommend this to be done around once a week. And unlike a traditional woodstove, it only takes a few minutes & you don’t really have to worry ash mess in the house.

And that’s it! That’s everything you need to do during the operating season to keep your outdoor wood boiler heating efficiently and effectively.

Optimum Heating with Eco Friendly and Energy Efficient Outdoor Wood Boilers for Homes and Farms

As we’ve discussed, the two big advantages of wood-burning boilers are their energy efficiency, low maintenance and reliance on an easily-obtainable renewable energy source. So, what exactly makes these systems so efficient?

The most efficient line of wood-burning boilers on the market use a process known as gasification. Essentially, gasification not only burns the wood in the firebox but also burns the smoke that is typically lost through the chimney in other models. This makes the boiler significantly more efficient than more traditional styles of wood-burning boilers. This is because it has a hot combustion area usually incorporating refractory cement that gets hot enough to ensure complete combustion allowing a heat exchange that is able to transfer more heat.

And not only does it nearly eliminate energy loss through the chimney, it means you use less wood throughout the year. While wood is a renewable energy source, using less of it for your heating needs is ideal for both your pocketbook and for the environment.

Several rural homes and farms are still reliant on boilers that burn oil and gas in 2023. Wood is a much cleaner and safer source of energy and is a great alternative for these old, highly-polluting boilers in rural settings when they reach the end of their lifespan. (Are Wood-burning Stoves Bad for the Environment?,” n.d.).


Q. How does a wood boiler connect to a forced-air system?

This can be done a lot easier than you think! A heat exchanger is installed in the plenum, just above your forced-air furnace. This heat exchanger, while it looks a little different, works exactly like the one already inside your furnace. The heat exchanger operates in a similar fashion to the coil on a radiator. 

The heat exchanger in your furnace works by transferring heat from the burner box into the air that it pushes throughout your home by use of a fan. The heat exchanger for your wood boiler works just the same way, only it transfers the heat from the hot water into the air.

When interfaced with your forced-air system, it will utilize the furnace fan to move heat the same way. So unlike an indoor woodstove that heats some areas of your home well and leaves cold spots in others, a wood boiler connected to your existing forced-air system can provide the same heat distribution as a furnace does.

Q. What makes wood such a popular renewable energy source?

Wood is not only affordable and easily accessible in our area, it provides a sustainable, alternative energy source in a world where rising energy prices are creating concern for families across the board. Wood heating is a great choice for those looking to move away from gas and electric options.

Burning wood is considered carbon-neutral because it does not increase the amount of carbon dioxide (a regularly occurring molecule but also a greenhouse gas) cycling through the atmosphere. Carbon is continually cycling through all living plants and animals.

Tree growth and wood decomposition represent a short-term carbon cycle, where growing trees convert carbon dioxide to woody biomass and decomposing trees release carbon dioxide back into the atmosphere. Wood-Energy (2019)

Affordability, however, is probably the main attraction to wood as a source of heat. Oftentimes boiler owners will source their own wood from their land or buy it from another person in the community. Keeping business local is just another way to keep costs down for those reliant on wood-burning heat sources. For this reason, wood-burning boilers have become quite popular in rural communities across the country.

Q. Is burning wood bad for the environment?

Wood boilers and woodstoves are considered to be carbon neutral. As we know, trees absorb carbon dioxide and release oxygen throughout their lives. Carbon neutral essentially means that the carbon dioxide released from burning the wood is offset by the carbon dioxide the tree had removed from the environment when it was alive. (“Wood energy 101,” n.d.)

University of Minnesota professor emeritus Jim Bowyer is an expert in the type of analysis that involves calculating the emissions of certain actions. And trees, he said, have a significant relationship with CO2, one of the greenhouse gases that contribute to climate change.

As a tree grows, it captures carbon dioxide from the air, water moves up the trunk. Water and carbon dioxide combine in the presence of sunlight, and in the leaves, the process of photosynthesis takes place,” he said.

As part of photosynthesis, trees take in carbon dioxide, release oxygen and produce sugars.

“Those sugars move down the trunk of the tree. Those sugars are converted to wood,” Bowyer said.

Trees, of course, don’t live forever. One way to lock in that carbon capture for the long term is by harvesting a tree for lumber before it decomposes and allowing new trees to grow it its place.

But if a tree is left to die and decompose, Bowyer said, “the decay process is exactly the reverse of photosynthesis.”

He explains: “Water is used by decay fungi, and as the fungi works on the wood, the wood is then converted back to carbon dioxide.”

Burning that wood for heat speeds up the process, he said, but it’s carbon neutral, as long as it’s managed in a way that allows for new growth and new opportunities for carbon absorption.

“Wood is a renewable resource, assuming that the forests that the wood is taken from are managed sustainably,” Bowyer said

Another, small way to make wood-burning heat sources more eco-friendly is to reuse and repurose the wood ash instead of disposing it. Often discarded, wood ash is high in calcium and can be a useful tool for your garden. It can help neutralize acidic soil and assist with the nutritional needs of certain food-bearing plants. (Schildgen, Bob, 2017). Ash can also be used to provide traction for walking and driving on ice instead of sand, salt and ice-melt.

Q. Does the type of wood I burn matter?

While the type of wood you burn can definitely make a difference, the biggest reason you might not be getting the most efficiency out of you wood-burning boiler is moisture content.

Green wood is extremely high in moisture. If you burn green wood, you are spending precious energy to burn off that moisture before the wood is able to be used as fuel, thus decreasing the efficiency of your boiler. Seasoning, or drying, your firewood is a crucial step in ensuring your boiler has efficient fuel to burn throughout the season. Make sure to store firewood in a covered area that is safe from moisture and stack the wood so outdoor air is able to circulate through it. Stacking wood too close can create moisture and wood rot within the woodpile.

The type of wood you burn does matter quite a bit if you are looking to get the most out of your outdoor boiler. Hardwood makes for better fuel in a wood-burning sytem than softwood. Hardwoods generally come from slow-growing trees. Once harvested and dried, hardwoods are significantly denser than softwoods. This means they are a far superior fuel source. (The Stove Yard, n.d.) Popular hardwoods are: Ash, Oak, Hickory and Maple.

Your boiler will still burn softwoods but it is a less efficient fuel. These trees are fast-growing as as a result, their wood is less dense. (The Stove Yard, n.d.) You will likely have to stock the boiler more often and in turn, you’ll use far more wood throughout the winter.

Q. What do I do with my wood boiler during the summer?

Wood-burning boilers have a shutdown process after heating season has ended. This is a fairly simple task to complete and we’ve found that most homeowners are more than comfortable doing it themselves.

The shutdown process involves cleaning the unit, removing all ash from the firebox, covering the chimney and adding water to the tank so it remains full throughout the off season. It is also recommended to add a water treatment for longevity of the system. 

You can send us a water sample for FREE testing, you will be advised if any remedy is required on the same. 

Please allow approximately four weeks for your sample to be received and processed. We will test the water and send you the analysis, via email or mail, if you do not have an email address.

Should you have any questions in regards to submitting a sample or regarding your results, please e-mail us at info@portageandmainboilers.com or call us toll free 1-800-561-0700. Read more on this link.

We do recommend keeping the pump circulating through the off season as well to prevent any sediment from settling in the boiler.


Are Wood-burning Stoves Bad for the Environment? (n.d.). Conserve Energy Future. https://www.conserve-energy-future.com/are-wood-burning-stoves-bad-for-environment.php

Schildgen, Bob. (2017, February 19). Hey Mr. Green! What should I do with ashes from a Woodstove fireplace? Sierra Club. https://www.sierraclub.org/sierra/ask-mr-green/hey-mr-green-what-should-i-do-ashes-woodstove-fireplace

The Stove Yard. (n.d.). What is the best wood to burn? https://www.thestoveyard.com/pages/what-is-the-best-wood-to-burn

Wood-Energy. (2019, September 5). Is burning wood carbon-neutral? – Wood Energy. https://wood-energy.extension.org/is-burning-wood-carbon-neutral/

Dunbar, E. (2019, November 9). Climate Curious: Is burning wood for heat carbon neutral? MPR News. https://www.mprnews.org/story/2019/11/09/climate-curious-is-burning-wood-for-heat-carbon-neutral

Wood energy 101. (n.d.). UW-Madison Wisconsin Energy Efficiency and Renewable Energy. https://fyi.extension.wisc.edu/energy/wisconsin-state-wood-energy-team/learning/wood-energy-101

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About Portage & Main

Our head office is located in Prince Albert, Saskatchewan, Canada. Our dealer network spans North America and we would be glad to put you in touch with one of our knowledgeable agents. Our staff oversees the development of new products, monitors production, designs heating systems, and offers tech support for installers. All our wood furnaces are designed for installation outdoors and deliver wood heat indoors.







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