Outdoor wood boilers, which burn wood or pellets to generate heat, serve as an economical alternative to traditional gas or electric heating systems. Unfortunately, wood boilers are also known for their relatively poor efficiency, which ranges from 28 to 55 percent, according to "Mother Earth News." Taking steps to improve the efficiency of your wood boiler allows you to generate the same amount of heat with less wood and also results in a significant reduction in smoke emissions and air pollution.
Keep your outdoor wood boiler running as efficiently as possible by choosing the right wood for the job. Stick to dry, seasoned wood only, and avoid using wet, green or freshly cut wood. All firewood must dry for six to 12 months after splitting, according to the California Air Resources Board. Check your firewood with a moisture meter before loading it into your boiler, and only use wood with a moisture rating of 20 percent or less. Never burn trash, tires or substances other than wood. Hard woods like oak and hickory provide a longer burn, making them more efficient than soft woods for cold days. while softer woods with a lower energy content provide less heat for the "shoulder" season. The Hearth, Patio and Barbecue Association recommends following the boiler manufacturer's recommendations regarding loading amounts and times to maximize efficiency.
Follow Maintenance Recommendations
Prevent problems and optimize efficiency by following the manufacturer's maintenance recommendations for your wood boiler. Generally, this means removing ash every few weeks or once a month, as well as scheduling an annual inspection to remove creosote.
Add a Catalytic Converter
Modern wood-burning appliances often incorporate a catalytic converter or combuster, which burns smoke at a lower temperature than normal. This allows the stove to generate usable heat from smoke that would otherwise go up the chimney or out a vent, and it also helps to reduce pollution. Several manufacturers offer add-on catalytic converters to improve efficiency and performance for wood boilers. These devices are typically installed in or around the firebox, and some are simple enough for homeowners to install without the help of a professional.
Consider an Upgrade
The U.S. Environmental Protection Agency offers voluntary standards for wood boilers, also known as hydronic heaters. Boilers that meet these standards are significantly more efficient than nonqualified heaters, according to the EPA. Units that meet EPA Phase 1 requirements feature an orange hang tag and are 70 percent cleaner than nonqualified units. Boilers with a white tag meet Phase 2 standards and are 90 percent cleaner than nonqualified units. If you have an older, unqualified wood boiler, consider upgrading to realize significant efficiency and environmental benefits.
- Mother Earth News: Coming Soon -- More Efficient, Cleaner Outdoor Wood Boilers
- U.S. Environmental Protection Agency: Consumers -- Choosing Appliances
- U.S. Environmental Protection Agency: EPA’s Hydronic Heater Voluntary Partnership Program
- U.S. Environmental Protection Agency: Consumers -- Energy Efficiency and Wood-Burning Stoves and Fireplaces
- California Air Resources Board: Wood Burning Handbook
- Hearth, Patio and Barbecue Association: Outdoor Wood Furnaces
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