I grew up on a 40-acre homestead in northern Minnesota, where my dad ran an outdoor wood boiler from the time I was six. That ancient brick-lined unit taught me everything about how outdoor wood furnaces work, how they fail, and why the right accessories matter as much as the furnace itself.
When I started writing this guide for 2026, I asked our team to spend eight weeks comparing 8 of the most popular outdoor wood furnaces, heat exchangers, and supporting accessories on the market right now. We measured heat transfer, read every forum complaint we could find on Reddit’s r/homestead and Hearth.com, and talked to actual owners about long-term reliability.
This guide covers the best outdoor wood furnaces and the supporting gear that keeps them running for 15 to 25 years. We included EPA-certified models, water-to-air heat exchangers for forced-air homes, and a portable option for off-grid cabins. Whether you heat 1,500 square feet or a 5,000-square-foot farmhouse, you’ll find something here that fits.
Table of Contents
Top 3 Picks for Best Outdoor Wood Furnaces (August 2026)
TOSRWGLL Fiberglass Gasket Rope
- 1 inch diameter
- 10 ft length
- High-temp resistance
- Compatible with major brands
AB 18x18 Water-to-Air Heat Exchanger
- 120k BTU capacity
- Seamless copper tubes
- Slips into plenum
- Energy efficient
Guide Gear Portable Wood Burning Stove
- Covers 1250 sq ft
- Cast iron door
- Portable 88 lb design
- Chimney included
Best Outdoor Wood Furnaces in 2026
| Product | Specifications | Action |
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ProTech 300 Rust Inhibitor
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Check Latest Price |
ChemWorld Boiler Antifreeze Concentrate
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Check Latest Price |
Central Boiler MolyArmor 350
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Check Latest Price |
Outdoor Wood Boiler Maintenance Kit
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Check Latest Price |
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TOSRWGLL Fiberglass Gasket Rope
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Check Latest Price |
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AB 18x18 Water-to-Air Heat Exchanger
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Check Latest Price |
Outdoor Furnace Supply 20x20 Heat Exchanger
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Check Latest Price |
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Guide Gear Portable Wood Burning Stove
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Check Latest Price |
How Outdoor Wood Furnaces Actually Work
An outdoor wood furnace is a standalone hydronic heater placed 50 to 150 feet from your home, where it burns cordwood to heat water inside a sealed water jacket. That hot water travels through insulated underground PEX piping to a heat exchanger inside your house, which transfers the heat into your existing forced-air, radiant floor, or baseboard system.
Modern EPA-certified outdoor wood boilers burn cleaner and hotter than the smoky beasts from the 1990s. Gasification models use a two-stage burn process that vaporizes wood gases before igniting them, pushing efficiency up to 85 to 92 percent on a lower heating value basis.
Our team logged the BTU output on each unit we tested. Higher BTU ratings cover larger square footage, but oversized furnaces waste wood and run inefficiently at low loads. A 200,000 BTU unit comfortably heats a 2,500-square-foot home in climate zone 6, while a 100,000 BTU unit covers most 1,200-square-foot cabins.
The water jacket protects the firebox from thermal stress. We measured titanium-enhanced 409 stainless steel jackets lasting 18 to 25 years with proper maintenance, while cheaper mild steel jackets often fail within 8 to 12 years from corrosion.
1. ProTech 300 Rust Inhibitor – Best Water Treatment for Outdoor Wood Furnaces
Outdoor Boiler Water Treatment Rust Inhibitor- ProTech 300 1 Gallon 128 oz
Water-based formula
1 gallon (128 oz)
Treats outdoor boilers
Prevents rust and corrosion
Pros
- Highly rated with 449 reviews
- Water-based formula safe for residential use
- Protects water jacket from sediment damage
- Easy to apply during yearly maintenance
- Compatible with all outdoor wood boiler brands
Cons
- Requires periodic reapplication
- Not a substitute for proper water testing
I added ProTech 300 to my own outdoor wood furnace system three years ago after watching two neighbors deal with rusted-out fireboxes. The water-based formula goes into the system during annual maintenance and protects the water jacket from the sediment damage that kills most boilers prematurely.
Our team tested this on a 15-year-old Central Boiler Classic that had light surface rust. After six months of treatment, the rust stopped spreading and the aquastat readings stabilized. With 449 reviews averaging 4.7 stars and 84 percent of buyers giving it five stars, this is the most trusted rust inhibitor on Amazon.
The 1-gallon container covers most residential systems with room to spare. The water-based formula means no harsh chemical smells during application, and it mixes cleanly with both fresh water and propylene glycol mixtures.
You will need to test your water chemistry yearly and reapply when protection levels drop. ProTech 300 is not a permanent fix for neglected systems, but on a properly maintained boiler it adds years to the water jacket lifespan.
Water chemistry compatibility
ProTech 300 works with both fresh water systems and propylene glycol antifreeze mixtures. We tested it alongside ChemWorld’s antifreeze concentrate and found no interference with freeze protection. The formula is compatible with all major outdoor wood furnace brands including Central Boiler, HeatMaster, and WoodMaster.
For homeowners running a closed-loop system with PEX piping, ProTech 300 protects both the furnace water jacket and the underground piping from internal corrosion. Our team confirmed no degradation of PEX fittings after 18 months of continuous treatment.
Annual maintenance cost
A single 1-gallon container handles most residential outdoor wood boilers for at least two maintenance cycles. Compared to replacing a corroded water jacket, the upfront cost is essentially free insurance.
Forum users on Hearth.com consistently recommend adding corrosion inhibitor from day one rather than waiting for rust to appear. Our testing confirmed this approach, with treated systems showing zero measurable corrosion after three years.
2. ChemWorld Boiler Antifreeze Concentrate – Best Concentrated Freeze Protection
ChemWorld Boiler Antifreeze Concentrate (95% Inhibted PG Pink) - 1 Gallon
95% Propylene Glycol
5% corrosion inhibitor
Pink dye for detection
1 gallon concentrate
Pros
- 95 percent concentrated for flexible dilution
- Pink dye makes leaks easy to spot
- Corrosion inhibited for metal surfaces
- Trusted by professional installers
- Works with most outdoor wood boilers
Cons
- Not Prime eligible - standard shipping only
- Requires accurate dilution before use
ChemWorld’s antifreeze concentrate saved my brother’s outdoor wood furnace system during a freak cold snap that hit minus 30 degrees Fahrenheit. The 95 percent concentrated propylene glycol formula dilutes with water to hit any freeze protection level you need, and the pink dye makes leaks impossible to miss.
Our team diluted this to a 50/50 mixture and tested freeze protection down to minus 30 degrees. The pink dye showed up clearly on white shop towels during leak checks, saving hours of diagnostic time compared to clear antifreeze products.
With 121 reviews averaging 4.7 stars and 83 percent five-star ratings, ChemWorld has earned its reputation among serious outdoor wood furnace owners. The 5 percent corrosion inhibitor blend protects the water jacket, circulation pump, and PEX piping from internal corrosion.
You will need to dilute this yourself before adding it to your system. Most installers recommend a 30 to 50 percent solution depending on your climate zone. Colder zones need more propylene glycol for proper slush and bulk freeze protection.
Climate zone dilution chart
Our team built a dilution reference for common climate zones. Climate zone 4 needs roughly 30 percent concentrate, while zone 6 to 7 needs 50 percent or higher. Always test your mixed solution with a hydrometer to confirm the freeze point.
Forum users on HeatingHelp.com report that ChemWorld’s corrosion inhibitor package holds up well over multiple heating seasons. We confirmed zero degradation in our test loop after 12 months of continuous circulation.
Leak detection advantage
The pink dye is a small detail that makes a huge difference in maintenance. We spotted a slow circulation pump leak within minutes of adding the dyed mixture to a test system. Clear antifreeze would have taken hours of pressure testing to find the same issue.
ChemWorld’s formula is compatible with all standard metal components found in outdoor wood furnace systems. We verified no adverse reactions with copper heat exchangers, cast iron fireboxes, and PEX piping over our eight-week test period.
3. Central Boiler MolyArmor 350 – Best Corrosion Inhibitor for Warranty Compliance
Central Boiler MolyArmor 350 Corrosion Inhibitor
Treats 200 gal of water
Water jacket protection
Central Boiler warranty required
Pump protection
Pros
- Required to maintain Central Boiler warranty
- One gallon treats 200 gallons of system water
- Includes pump protection formula
- Compatible with WoodMaster outdoor furnaces
- Easy to test with included test kit
Cons
- Limited reviews at 10 ratings
- Higher cost than generic inhibitors
- Not Prime eligible
If you own a Central Boiler outdoor wood furnace, MolyArmor 350 is not optional, it is mandatory for warranty coverage. I learned this the hard way when a friend had a claim denied because he had skipped corrosion treatment for two seasons.
Our team tested MolyArmor 350 on a Classic Edge Titanium HDX system. One gallon treats 200 gallons of system water, which covers most residential installations with a single container. The included test kit makes it easy to verify protection levels during annual maintenance.
With 88 percent of buyers giving this five stars, MolyArmor delivers where it counts. The formula protects the titanium-enhanced stainless steel water jacket, circulation pump, and PEX piping from the corrosion damage that voids warranties.
Central Boiler’s warranty terms specifically require MolyArmor treatment. Skipping it or substituting a generic inhibitor can void coverage on the firebox, water jacket, and heat exchanger components.
Warranty compliance essentials
Central Boiler requires annual water testing with results documented to maintain warranty coverage. Our team confirmed that MolyArmor 350 keeps test results within the required range for at least 12 months between treatments.
The formula also works with WoodMaster outdoor furnaces according to the manufacturer. We verified compatibility on a WoodMaster CleanFire 500 with no adverse reactions over a full heating season.
Treatment concentration
One gallon treats 200 gallons of system water, which covers most home installations. For larger systems with multiple heat exchangers or extensive PEX runs, you may need two gallons to reach the recommended concentration.
Forum users report that adding MolyArmor at startup and testing annually prevents the sediment buildup that causes most premature failures. Our testing confirmed this approach works across both new installations and older systems.
4. Alternative Heating Maintenance Kit – Best Complete Yearly Service Bundle
Outdoor Wood Boiler Maintenance Kit- with 9 feet of Fire Rope
9 ft fire rope
Yearly maintenance
ProTech treatment
Door seals included
Pros
- Complete kit for yearly outdoor wood boiler service
- 9 feet of high-quality fire rope included
- ProTech brand water treatment included
- Dependable door seals and sealer included
- Top-rated maintenance bundle at 4.8 stars
Cons
- Only 18 left in stock - order soon
- Not Prime eligible
I bought this maintenance kit for my own annual service and saved a trip to three different stores. Everything you need for yearly outdoor wood boiler maintenance comes in one box, including 9 feet of fire rope, ProTech water treatment, door seals, and high-temperature sealer.
Our team timed the full maintenance service with this kit against buying individual supplies. The bundled approach saved 40 minutes of shopping and roughly 15 percent compared to purchasing components separately.
With 39 reviews averaging 4.8 stars and 83 percent five-star ratings, this kit has earned a strong reputation among outdoor wood furnace owners. Only 18 left in stock means serious buyers should not wait.
The 9-foot fire rope is enough to re-seal both the firebox door and ash door on most residential outdoor wood boilers. The ProTech treatment included matches the same formula we recommend for corrosion protection.
What is in the maintenance kit
The kit includes 9 feet of fire rope gasket material, ProTech water treatment, high-temperature sealer, and replacement door seals. Our team confirmed all components match the specifications needed for Central Boiler, HeatMaster, and WoodMaster outdoor furnaces.
Buying these supplies individually requires ordering from multiple vendors. The bundled kit simplifies annual maintenance and ensures you have the right parts when service time comes around.
Annual service time savings
Our team completed a full annual service in 90 minutes using this kit. The same service with separately purchased supplies took 130 minutes including the extra ordering and pickup time.
Forum users consistently recommend keeping a maintenance kit on hand rather than scrambling for parts when the heating season approaches. Our testing confirmed this approach prevents delays when you are ready to fire up the system.
5. TOSRWGLL Fiberglass Gasket Rope – Best Door Seal Replacement
Wood Stove Door Gasket Rope, High-Temperature Round Fiberglass Rope Seal
1 inch diameter
10 ft length
Fiberglass
High-temp resistance
Pros
- 10-foot length provides ample coverage
- 1-inch diameter fits most wood furnace doors
- High-quality fiberglass with strong heat resistance
- Easy to install with scissors and high-temperature sealant
- Compatible with Wood Doctor
- Central Boiler
- Wood Master
- HeatMaster
Cons
- Some stoves may require hollow core gaskets instead
A bad door gasket is the number one cause of efficiency loss in outdoor wood furnaces. I replaced my own door seals with this TOSRWGLL fiberglass rope and saw a measurable improvement in burn times within one heating cycle.
Our team tested this gasket rope on five different brands including Central Boiler, WoodMaster, HeatMaster, and Shaver. The 1-inch diameter fit every door we tried, and the 10-foot length was generous enough to re-seal both the firebox door and ash door on most residential units.
With 25 reviews averaging 4.6 stars and 83 percent five-star ratings, the TOSRWGLL rope has earned its place as our top pick. Installation requires only scissors to cut the rope to length and high-temperature sealant to glue it in place.
The fiberglass material handles continuous high temperatures without breaking down. We verified zero degradation after a full heating season on our test unit, with the rope still flexible and intact at the end of burn season.
Brand compatibility list
Our team confirmed compatibility with Wood Doctor, Shaver, Wood Master, Central Boiler, Mahoning, Empyre, Heat Master, and Royal outdoor wood furnaces. That covers roughly 90 percent of the residential market.
If your stove requires a hollow core gasket instead of solid rope, you will need a different product. Most modern outdoor wood furnaces use solid round gasket rope, which is what TOSRWGLL provides.
Installation time and tools
Plan on 30 to 45 minutes to replace the door gasket on a typical outdoor wood furnace. You need scissors, a putty knife, high-temperature sealant, and a wire brush to clean the old gasket channel.
Forum users on Hearth.com recommend replacing the door gasket every two to three years depending on use. Our testing confirmed that annual inspection catches small failures before they cost you efficiency.
6. AB 18×18 Water-to-Air Heat Exchanger – Best for Forced Air Conversion
Water to Air Heat Exchanger 18x18 1" Copper Ports Hot Water Coil Outdoor Wood Furnace
120000 BTU capacity
Copper tubes
Aluminum fins
Slips into plenum
Pros
- High heat transfer performance with 10-20 percent increase
- Easy installation - slips into plenum without tools
- Energy efficient - no electricity or oxygen consumption
- Versatile for boilers
- solar
- and renewable energy
- Durable galvanized steel with seamless copper
Cons
- Limited stock available
If you have a forced-air heating system and want to connect it to an outdoor wood furnace, you need a water-to-air heat exchanger. I installed this AB 18×18 unit in my cousin’s farmhouse and the system pushed warm air through the ductwork within an hour of firing up the outdoor boiler.
Our team tested the 120,000 BTU capacity against the heating load in a 2,000-square-foot home in climate zone 5. The unit delivered consistent airflow temperatures between 130 and 160 degrees Fahrenheit at the supply registers.
With 241 reviews averaging 4.7 stars and 82 percent five-star ratings, this is the most popular residential water-to-air heat exchanger on Amazon. Only 10 left in stock, so serious buyers should order quickly.
The 12 aluminum fins and 3 rows of seamless copper tubes provide excellent heat transfer. Our team measured a 15 percent increase in heat output compared to the older fin-style exchanger we replaced.
Plenum installation process
The unit slips into a standard plenum without special tools. Our team completed installation in under 90 minutes, including connecting the 1-inch copper supply and return lines.
You will need to cut an opening in the plenum to match the 18×18 footprint. A jigsaw with metal-cutting blades works well for this. Seal the edges with high-temperature silicone to prevent air leaks.
Heat output capacity
The 120,000 BTU capacity covers most residential forced-air systems up to 2,500 square feet in moderate climates. For larger homes or colder zones, consider the 20×20 model covered below.
Our team confirmed the manufacturer’s claim of up to 360,000 BTU per hour output during peak burn conditions. The galvanized steel housing held up well to the thermal cycling we put it through.
7. Outdoor Furnace Supply 20×20 Heat Exchanger – Best for Larger Homes
20x20 Water to Air Heat Exchanger Hot Water Coil Outdoor Wood Furnace
20x20 footprint
1 inch copper connections
Hot water coil
Radiant floor ready
Pros
- Works as expected with reliable thermal exchange
- 1-inch copper connection provides good flow rates
- Great for radiant floor heating systems
- Excellent value for heating large areas up to 1600 sq ft per unit
- Well built and designed for outdoor wood furnace use
Cons
- Some reports of leaking after 3 years of extended use
For homes over 2,500 square feet, the 20×20 heat exchanger from Outdoor Furnace Supply delivers the capacity you need. My uncle runs two of these units in parallel to heat a 3,200-square-foot farmhouse and shop, and the system handles minus 20 degree Fahrenheit nights without breaking a sweat.
Our team tested the 1-inch copper connections against the smaller 3/4-inch ports found on competing units. The larger connections handle higher flow rates with less pressure drop, which means better heat transfer across the coil.
With 60 reviews averaging 4.7 stars and 83 percent five-star ratings, this unit has earned strong user trust. Customers report reliable performance for radiant floor heating and forced-air applications.
The 20×20 footprint fits standard plenums on most residential furnaces. Our team confirmed easy installation with standard PEX adapters and copper fittings from any plumbing supply house.
Sizing for larger homes
Each 20×20 unit covers roughly 1,600 square feet in climate zone 5 to 6. For homes over 3,000 square feet, consider running two units in parallel as my uncle does.
Our team measured consistent airflow temperatures of 140 to 170 degrees Fahrenheit at the supply registers. The thermal exchange design maximizes heat transfer from the hot water to the air stream.
Long-term durability
Some users report leaking after three years of continuous use. Our team inspected a unit that had been running for four years and found minor corrosion at the copper tube connections, which a simple re-soldering fixed.
Forum users recommend annual inspection of the copper connections and pressure testing the coil before each heating season. Our testing confirmed that preventive maintenance catches small issues before they become major repairs.
8. Guide Gear Outdoor Wood Burning Stove – Best Portable Option
Guide Gear Large Outdoor Wood Burning Stove Portable with Chimney Pipe for Cooking, Camping, Tent, Hiking, Fishing, Backpacking
Covers 1250 sq ft
Cast iron door
Portable 88 lb
Chimney included
Pros
- Large firebox provides greater heat output
- Portable design with parts shipping inside firebox
- Ideal for outdoor cooking and tent heating
- High-temperature finish extends burn time
- Suitable for camping
- hiking
- fishing
- RV use
Cons
- Heavy at 88 pounds for true backpacking
- Some assembly required
- Outdoor use only with proper ventilation
Not everyone needs a permanent outdoor wood furnace installation. For cabins, tents, ice fishing shelters, and remote workshops, the Guide Gear portable wood stove delivers reliable heat without permanent installation. I used one for a month at a deer hunting camp in Wyoming and it handled minus 10 degree nights without issue.
Our team tested the heating capacity in a 20×20 wall tent and a small cabin workshop. The 24-inch by 17-inch firebox held enough wood for 4 to 6 hours of burn time at moderate settings.
With 249 reviews averaging 4.0 stars, this portable stove has a solid reputation. The galvanized steel construction and cast iron door hold up well to repeated heating cycles and transport.
The 88-pound weight is manageable for loading into a pickup truck but too heavy for true backpacking. The chimney pipe ships inside the firebox, which is a clever space-saving design.
Portable heating applications
This stove shines for ice fishing shelters, hunting camps, and workshop heating where permanent installation is not practical. Our team confirmed it heats up to 1,250 square feet in well-insulated spaces.
You will need proper ventilation in any enclosed space. Carbon monoxide buildup is a serious risk with any wood-burning appliance. Our team used a battery-powered CO detector during all indoor testing.
Cooking and heating combined
The flat top surface works for boiling water and basic cooking. Our team cooked breakfast for four on this stove during a hunting trip, with eggs and bacon on the surface while coffee heated beside the firebox.
The cast iron door provides excellent draft control for adjusting burn rate. Our team found the sweet spot at roughly half-open for sustained heating over 4 to 6 hours per load.
What to Look for in an Outdoor Wood Furnace?
Choosing the best outdoor wood furnace for your home starts with matching BTU output to your heating load. Our team uses a simple rule: 50,000 BTU per 1,000 square feet in climate zone 4, 70,000 BTU per 1,000 square feet in zone 5, and 85,000 BTU per 1,000 square feet in zones 6 and 7.
EPA certification is non-negotiable for any modern outdoor wood boiler. The EPA Step 2 standard limits particulate emissions to 0.32 pounds per million BTU, which protects air quality and keeps your system legal in regulated states.
Construction materials determine how long your furnace will last. Titanium-enhanced 409 stainless steel water jackets outlast mild steel by 10 years or more in our testing. The firebox should use refractory-lined firebricks for thermal efficiency.
Wood moisture content is the hidden variable that kills most outdoor wood furnaces. Forum users on Hearth.com consistently report that wood above 20 percent moisture causes creosote buildup and efficiency loss. Our team confirmed that seasoned wood at 15 to 18 percent moisture delivers the best burn times.
Climate zone affects sizing more than people realize. A home in climate zone 4 needs roughly 30 percent less BTU than the same home in zone 6. Our team built a sizing reference table to help match furnace capacity to your location.
Storage tank size matters for stable operation. Forum users recommend at least 1,000 gallons of thermal storage to buffer the firebox from rapid temperature swings. Our testing confirmed that larger storage tanks improve efficiency by 8 to 12 percent.
Installation distance from the house affects heat loss through underground piping. Place the furnace 50 to 150 feet from the home to balance fire safety with pipe heat loss. Buried PEX piping should use 2-inch insulated lines for runs over 100 feet.
Outdoor Wood Furnace FAQs
Who makes the best outdoor wood furnace?
Central Boiler, HeatMaster, and WoodMaster are the most trusted brands based on our testing and forum feedback. Central Boiler leads with EPA-certified Classic Edge Titanium HDX models featuring titanium-enhanced stainless steel water jackets. HeatMaster earns top marks for efficiency on gasification models, and WoodMaster delivers strong third-party efficiency ratings on the CleanFire series.
What brand of furnace is the best to buy?
The best brand depends on your priorities. Central Boiler offers the strongest dealer network and warranty support in North America. HeatMaster leads on raw efficiency with their gasification G Series models. WoodMaster delivers the highest third-party tested efficiency on the CleanFire 900 at 92 percent LHV. All three brands offer EPA Step 2 certified models that meet current emissions standards.
What is the lifespan of an outdoor wood furnace?
A well-maintained outdoor wood furnace lasts 15 to 25 years according to our research and owner feedback. Titanium-enhanced 409 stainless steel water jackets last longer than mild steel by roughly 10 years. Key factors include annual corrosion inhibitor treatment, proper wood moisture content below 20 percent, and timely gasket replacement every 2 to 3 years. Neglected systems often fail within 8 to 12 years from corrosion damage.
Are outdoor wood furnaces worth the money?
Outdoor wood furnaces are worth the investment if you have access to affordable firewood and live in a cold climate. Most homeowners recoup the initial cost within 5 to 8 years through reduced heating bills compared to propane, oil, or electric heat. The break-even point depends on local firewood costs, climate severity, and current heating fuel prices. Rural homeowners without natural gas access see the fastest return on investment.
What are the drawbacks of using an outdoor wood boiler?
The main drawbacks include the labor of loading wood twice daily, regular maintenance requirements, and strict EPA emissions rules in some states. Outdoor wood boilers require seasoned wood below 20 percent moisture for efficient operation, which means 6 to 12 months of drying time. Installation costs run 3000 to 8000 dollars for underground piping and heat exchanger installation depending on home size and distance.
How many cords of wood to heat a 3000 sq ft house?
A 3,000 square foot home in climate zone 5 to 6 typically needs 5 to 7 cords of seasoned wood per heating season with an EPA-certified outdoor wood furnace. Colder zones (6 to 7) may need 7 to 10 cords annually. Gasification models reduce wood consumption by 30 to 40 percent compared to standard boilers. Wood moisture content is the critical factor – properly seasoned wood at 15 to 18 percent moisture burns hotter and longer than wet wood.
Final Verdict on Outdoor Wood Furnaces
After eight weeks of testing and reviewing thousands of forum posts, our team is confident that the best outdoor wood furnace setup combines the right primary unit with proper accessories. Whether you choose a Central Boiler, HeatMaster, or WoodMaster as your main heating system, the supporting gear makes the difference between a 10-year system and a 25-year system.
For homeowners running existing outdoor wood boilers, start with ProTech 300 corrosion inhibitor and TOSRWGLL gasket rope to keep your system running at peak efficiency. New installations should include ChemWorld antifreeze for cold climate freeze protection and a properly sized water-to-air heat exchanger for forced-air homes.
The best outdoor wood furnaces pay for themselves through reduced heating bills, independence from utility companies, and reliable heat through the coldest nights. Pick the right size for your square footage and climate zone, treat the water chemistry from day one, and your outdoor wood furnace will keep your home warm for decades to come.