Wood Boiler Heating with an Indoor Wood Boiler

Fröling Indoor Wood Boilers

house with wood boiler in the winterWood boilers are more popular than ever as homeowners search for alternative heating solutions. Wood boilers for home heating are a modern concept that cuts down fossil fuel use and heating costs. Replace your entire heating system with a wood burner and experience the benefits after a quick installation

Tarm Biomass is a leading supplier of high-efficiency wood-burning boilers. We walk you through the sales process from beginning to end and help you find the ideal indoor wood boiler. If you are looking to replace an outdoor wood boiler or switch to wood-sourced heat for your home, Tarm Biomass will provide suitable materials. 

An Overview of Indoor Wood Boiler Systems

FHG FlameFire has been a constant source of heat and light across cultures for thousands of years. With modern technology, we can use wood as an eco-friendly substitute for fossil fuels to heat our homes efficiently. The basic questions many people ask about wood-fired boilers include: 

What is a Wood-Burning Boiler?

A wood boiler burns firewood in a controlled chamber to generate heat, which then transfers to your water tank or directly to your home. The main difference between a wood boiler and a fossil-fueled boiler is the fuel source. Wood fuel has positive impacts on fuel costs, carbon emissions, and the local economy. 

Two types of wood boilers exist — indoor and outdoor. Outdoor wood boilers are weatherproofed and transfer heat through pipes to the home, while indoor boilers sit conveniently inside your house. Tarm Biomass sells indoor wood boilers that suit your home's size and produce heat within your residence's confines.

How Does a Wood Boiler Work?

fröling s3 turbo shadow crossA basic wood boiler consists of a primary and secondary chamber, an ash box, water supply, and return connections, and a control system. The operator loads firewood into the primary chamber, where they then ignite the wood and allow it to start burning. As the wood begins to burn, the gases released from combustion pull into the secondary chamber, where they continue to burn to maximize heat output. Heat transfer tubes exchange heat to the water pipes to create hot water.

Since almost all gases and tars burn in the chamber, harmful smoke is significantly diminished. Wood boilers can combine with your existing furnace as a backup system or serve as your primary heat source year-round.

Wood boilers can connect to or replace existing heating furnaces and boilers with automatic controls.

Why Is a Wood Boiler Not a Stove?

Though some individuals use the terms "boiler" and "stove" interchangeably, these appliances are not the same. Boilers transfer heat from the wood into the water and pump it into your central heating supply, where it can then heat water for taps, showers, and various forms of radiators for space heat. 

Wood-burning stoves also burn wood to produce heat but are typically used to warm the air in a particular room or area. These stoves often include a decorative element, such as glass fire viewing windows for use in living areas.

Why is an Indoor Wood Boiler Not an Indoor Wood Furnace?

Wood boilers and furnaces are also substantially different in function. The primary difference between furnaces and hot water boilers is that furnaces heat air and hot water boilers heat water. Wood burning boilers heat water and transfer this heat via circulators and valves to radiant flooring systems, radiators, domestic water tanks, water to air heat exchangers and other heat emitters. Indoor wood furnaces heat the air, which is transported through a building's ductwork using a blower, to individual rooms and spaces.  Wood burning boilers can also use heat exchangers to heat air. For this reason, wood boilers can replace furnaces, but cast iron furnaces cannot replace wood boilers.

What to Consider When Purchasing a Wood Boiler System

When choosing a wood boiler for your home, you should first consider your lifestyle. We account for all known factors when assisting our customers in selecting the right wood-burning heater for their heating applications:


With our indoor wood boilers, you should have space to install and access the heater freely. Our wood-burning boilers are compact and easy to use, so they fit in most furnace rooms to transfer the heat throughout the house.

Home Size

Your home's size, construction, use, and location will determine what size heater you need. We provide multiple-size boilers and thermal storage tanks to optimize operation and efficiency.

Heat Distribution

Wood boilers normally connect directly into existing heat and hot water tank systems. We assist in heating system integration directly or through trained dealer representatives.

Cleaning and Maintenance

Keeping a wood-fired boiler clean will help retain efficiency and reduce smoke. Fröling wood boilers include maintenance-reducing designs, such as the heat exchanger efficiency optimization system. Our wood boilers contain their ash in convenient ash removal zones that are typically accessed once per week. 

With our wood boilers, maintenance is simple and infrequent. Regular cleaning and repairs when necessary will keep your boiler in great shape for many different seasons. We will happily point you in the right direction of a local maintenance and quality service provider for your boiler.

Fröling Indoor Wood Boilers From Tarm Biomass

S3 Wood Boiler2Wood heating with an indoor wood boiler can be a practical, enjoyable way to heat your home. Heating a home with the Fröling S3 Turbo indoor wood boiler is the most efficient way to capture heat energy from firewood. The S3 Turbo offers features like the easy-start ignition door and external heat exchange cleaning. The Fröling S3 Turbo has Lambda-controlled combustion, which ensures a clean, efficient burn. 

All boilers are safety-tested and -listed. If you are replacing an outdoor wood boiler, some states like New York pay cash bounties when outdoor cordwood boilers are replaced with indoor wood gasification boilers. For more information about these programs, explore our page on renewable energy incentives.

Fuel for the Indoor Wood Boiler


indoor wood boiler firewood

Wood is the most widely available and least expensive biomass fuel available. Burning firewood produced on one’s own land has the lowest carbon impact of all forms of wood-burning and therefore can be considered the most sustainable form of wood burning. Boiler owners who produce their own firewood as a byproduct of managing their woodlots will also realize the greatest savings and cost benefits.

Firewood is normally sold in units called cords. A cord of wood is a neat stack measuring 4 feet wide by 4 feet high and 8 feet long. The heat content of a cord will vary depending on the species of wood. A cord of mixed softwood will have a heat value of 17 or 18 million BTU, and a cord of mixed hardwood will have a heat value of 20 to 29 million BTU.

By way of comparison, a gallon of No. 2 fuel oil has a heat value of 140,000 BTU per gallon, and propane has 93,000 BTU per gallon. Please use our fuel cost comparison tool to calculate the relative fuel costs in your area.

You should thoroughly dry firewood before using it in wood boilers. Firewood moisture content impacts the efficiency of your wood boiler, meaning the lower the water content, the better. At a minimum, we recommend drying firewood every six months to a year to ensure the moisture is low enough to burn efficiently.

Advantages of Indoor Wood Boilers for Home Heating

As oil prices rise and homeowners become more concerned with their carbon footprint, wood heating has become an excellent alternative to fossil fuels. 

Some benefits of wood-burning boilers include:

  • Lower heating costs: Compared to fossil fuels, you save considerably more money on heating your home with wood boiler heating. Wood prices are less likely to fluctuate since wood fuel is renewable, local, and not subject to financial speculation.
  • Positive impact: Firewood has a nearly neutral impact on atmospheric carbon. Firewood harvest is commonplace in our backyards and is well understood. No mining, heavy manufacturing, or complicated refining and transportation is required. Buying wood from local sources also benefits your regional economy. 
  • Simple living and energy independence: With wood being a readily available, local resource, wood boilers allow you to save money and reduce your dependence on big energy conglomerates with ease. 

Along with these benefits, many states offer different incentives for wood boiler owners. You may also benefit from a 30% federal tax credit through the end of 2023 when you purchase an indoor wood stove with a boiler. Our wood boilers offer these advantages and more, and we can help you select the best one for your application.

Boilers for Sale From Tarm Biomass

Our goal is to help you improve your life with wood-burning whole-house heaters. To learn more about which biomass boiler is right for your home, or see what wood boilers are for sale, contact us online and we can help you get started.