Outdoor Forced Air Wood Furnace Vs Boiler

Outdoor Forced Air Wood Furnace vs. Boiler: A Comprehensive Comparison

The heating of residential and commercial properties with wood as a primary fuel source has seen a resurgence, driven by factors such as cost savings, renewable energy considerations, and a desire for energy independence. Two primary technologies facilitate this: outdoor forced air wood furnaces and outdoor wood boilers. While both provide heat by burning wood, they differ significantly in their operation, installation, and overall suitability for various applications. Understanding these differences is crucial for making an informed decision about which system best meets an individual's or organization's heating needs.

This article provides a detailed comparison of outdoor forced air wood furnaces and outdoor wood boilers, examining their operational principles, installation requirements, efficiency, maintenance needs, and environmental impact. This in-depth analysis aims to equip readers with the knowledge necessary to select the appropriate wood-burning heating solution for their specific circumstances.

Operational Principles: Heat Delivery Mechanisms

Outdoor forced air wood furnaces and outdoor wood boilers employ fundamentally different methods for delivering heat. An outdoor forced air wood furnace directly heats air, while an outdoor wood boiler heats water that then circulates to provide warmth.

Outdoor Forced Air Wood Furnace: This system functions similarly to a traditional forced air furnace. Wood is burned within a firebox, and the resulting heat is transferred to air circulated through a heat exchanger. A powerful blower fan then forces this heated air through a network of ducts into the building, distributing warmth throughout the space. These systems typically require a direct connection to the existing ductwork of the building they are heating.

Outdoor Wood Boiler: Also known as an outdoor wood-fired hydronic heater, this system heats water within a large, insulated firebox. The heated water is then pumped through insulated underground pipes to a heat exchanger inside the building. This heat exchanger can be connected to various heating systems, including radiant floor heating, baseboard radiators, or even a domestic hot water system. The hot water circulating through these systems releases heat into the living space.

Installation and Infrastructure Requirements

The installation process and required infrastructure for outdoor forced air furnaces and outdoor wood boilers differ considerably, impacting overall project cost and complexity.

Outdoor Forced Air Wood Furnace: Installation generally involves placing the furnace on a concrete pad outside the building. Critically, the furnace must be directly connected to the building's existing ductwork system. This can involve modifications to the ductwork to accommodate the furnace's output and airflow characteristics. Electrical connections are necessary for the blower fan and any control systems. Permit requirements vary depending on local regulations.

Outdoor Wood Boiler: Installation involves placing the boiler on a concrete pad, similar to a furnace. However, the crucial difference lies in the necessity to install insulated underground pipes that connect the boiler to the building. These pipes transport the heated water. Inside the building, a heat exchanger is required to transfer the heat from the water to the building's heating system. This may involve connecting to an existing hydronic system or installing a new one. Electrical connections power the circulation pump and control systems. Permits are required and often involve inspection of the underground piping and connections to the building's plumbing and heating systems.

The cost of installing underground piping can be significant, particularly for longer distances between the boiler and the building. Furthermore, the installation of a heat exchanger and potentially a new hydronic heating system adds to the overall cost of an outdoor wood boiler installation.

Efficiency and Heat Output Considerations

The efficiency of heat transfer and the range of heat output capabilities are important factors to consider when choosing between an outdoor forced air wood furnace and an outdoor wood boiler.

Outdoor Forced Air Wood Furnace: The direct heating of air allows for relatively rapid heating of a space. However, heat loss can occur through ductwork, especially if the ductwork is not properly insulated. The efficiency of heat transfer can also be affected by the design and cleanliness of the heat exchanger. Heat output can be adjusted by controlling the airflow and the amount of wood burned.

Outdoor Wood Boiler: While the initial heating of the water may take longer than directly heating air, the large volume of water in the boiler acts as a thermal storage reservoir. This can provide a more consistent and even heat distribution. However, heat loss can occur through the underground pipes, even with proper insulation. The efficiency of heat transfer at the heat exchanger inside the building also plays a role. Heat output can be regulated by controlling the water temperature and flow rate. The larger water volume also provides greater flexibility in meeting fluctuating heating demands.

Heat output capacity is a critical consideration. Furnaces are often rated based on BTU output, while boilers are often rated based on the volume of water they hold and the BTU output. Matching the system's heat output to the building's heating needs is essential for optimal efficiency and performance. An undersized system will struggle to maintain a comfortable temperature during peak demand, while an oversized system may cycle frequently, leading to wasted energy and increased wear and tear.

Fuel Consumption and Wood Handling

The amount of wood consumed and the effort required to handle the wood are practical considerations that impact the long-term cost and convenience of wood-fired heating.

Outdoor Forced Air Wood Furnace: Generally, forced air furnaces tend to burn wood at a faster rate compared to boilers. This is due to the more rapid heat transfer process and the need to maintain a constant airflow. The firebox size may also be smaller, requiring more frequent loading of wood. The type of wood and its moisture content significantly affect fuel consumption. Properly seasoned wood burns more efficiently and produces less smoke.

Outdoor Wood Boiler: Due to the thermal storage capacity of the water jacket, boilers often burn wood more slowly and steadily. The larger firebox allows for less frequent loading. However, the overall wood consumption over a heating season can still be substantial. Similar to furnaces, the type and moisture content of the wood are crucial factors. Using dry, seasoned wood is essential for efficient combustion and reduced emissions.

The physical demands of wood handling should not be overlooked. Both systems require the manual loading of wood, which can be physically strenuous. The availability of a wood source, the cost of wood, and the time required for cutting, splitting, and stacking wood should be carefully considered. Some individuals may choose to purchase pre-cut and split wood, while others may prefer to harvest their own wood.

Maintenance Requirements and Longevity

Routine maintenance is crucial for ensuring the efficient operation and longevity of both outdoor forced air wood furnaces and outdoor wood boilers.

Outdoor Forced Air Wood Furnace: Regular maintenance includes cleaning the heat exchanger to remove soot and ash buildup, which can reduce heat transfer efficiency. Inspecting and replacing the blower fan as needed is also important. Checking the ductwork for leaks and ensuring proper airflow are essential for optimal performance. The firebox should be inspected for any signs of damage or corrosion. Creosote buildup in the chimney needs to be regularly cleaned to prevent fire hazards.

Outdoor Wood Boiler: Regular maintenance includes cleaning the firebox and heat exchanger to remove ash and soot. Monitoring the water level and maintaining proper water chemistry is crucial to prevent corrosion and scale buildup. Inspecting the insulated underground pipes for leaks or damage is essential. Checking the circulation pump and heat exchanger inside the building is also necessary. Creosote buildup in the chimney needs to be regularly cleaned. Inspecting and maintaining the sacrificial anodes within the water jacket is crucial to extend the lifespan of the boiler.

The expected lifespan of both systems can vary depending on the quality of construction, the level of maintenance, and the operating conditions. Properly maintained systems can last for many years, while neglected systems may experience premature failure. Regular inspections and preventative maintenance are essential for maximizing the lifespan of both furnaces and boilers.

Environmental Impact and Emissions

The environmental impact of wood-fired heating systems is a growing concern. Emissions from burning wood can contribute to air pollution. Modern furnaces and boilers are designed to reduce emissions through improved combustion technology.

Outdoor Forced Air Wood Furnace: Older furnace designs tend to produce higher emissions compared to newer, EPA-certified models. Factors such as the type of wood, moisture content, and combustion efficiency influence emission levels. Newer furnaces often incorporate secondary combustion chambers and catalytic converters to reduce emissions. Proper operation and maintenance are essential for minimizing environmental impact.

Outdoor Wood Boiler: Similar to furnaces, older boiler designs typically produce higher emissions. Modern, EPA-certified boilers are designed to burn wood more cleanly and efficiently. They often incorporate advanced combustion technologies, such as gasification, to reduce emissions. Proper operation and maintenance are crucial for minimizing air pollution. The use of dry, seasoned wood is essential for clean burning.

Local regulations regarding wood-burning appliances may restrict the types of units that can be installed or require the use of specific emission control devices. It is important to check local regulations before purchasing and installing a wood-fired heating system. Utilizing EPA-certified models significantly reduces environmental impact compared to non-certified models.