Outdoor Wood Boilers

Popular choice raises pollution concerns
Outdoor wood boilers (OWBs) have become increasingly popular in the Northeast as domestic heating costs for oil, natural gas, and propane continue to rise.

The "classic" outdoor wood boilers that have been on the market for years have raised public health and environmental concerns. Fuel frequently burns incompletely, resulting in heavy smoke and high emissions.

The problem is compounded by the fact that the stacks on these devices are often shorter than surrounding structures and do not disperse smoke adequately, concentrating it near the ground. Burning materials other than clean, dry wood, such as tires, trash, painted or treated wood, only exacerbates the problem.

However, when operated according to manufacturers' instructions using best burn practices, efficient OWBs are a viable option to reduce heating costs using the Northeast's own renewable resource: wood.

Local, pending state regulations
Responding to concerns, some towns and municipalities in the Northeast have regulated the use of OWBs. Solutions adopted by various municipalities range from setback and stack-height requirements to zoning ordinances and, in some cases, outright bans on the boilers.

New Hampshire has passed legislation, effective January 1, 2009, to regulate the sale of OWBs, as well as setback requirements, stack height, and fuel use. Certain provisions went into effect on August 10. Other New England states are also considering regulation.

More efficient, cleaner OWBs available
To encourage manufacturers to get the more efficient models to the marketplace faster, the U.S. Environmental Protection Agency (EPA) adopted and began promoting voluntary standards for OWBs in 2006. OWBs that meet these standards are more than 70 percent cleaner than their earlier counterparts.

These newer models may cost up to 15 percent more than their less-efficient counterparts. This additional cost is recouped by more efficient combustion. Increased efficiency means more heat for your home and less up the stack.

Older models are still for sale in New Hampshire until January 1, 2009. On that date, only OWBs that meet the EPA's emission standards will be allowed for sale here.

Additionally, the new law defines setback and stack height requirements to ensure efficient smoke dispersal. OWB users are required to burn only clean wood. The legislation also gives municipalities authority to impose stricter regulations on OWB use with regard to zoning, setbacks, and stack heights.

Considerations for prospective OWB buyers
Whether you are considering the purchase and installation of an outdoor wood boiler before the end of 2008 or after January 1, 2009, consider:

• Does your town have any regulations in place governing OWB installation and use?
• Do you have a sufficient source of clean fuel for an OWB?
• Are you willing to provide the additional labor necessary to prepare fuel (cut and stack firewood) and load the boiler?
  

Cost varies according to the model and the size of the space you want to heat
Units for residential use can range from $5,000 to $10,000. Other factors may add significantly to this initial purchase cost:

• Siting the boiler appropriately on a pad. (Do you have level ground on which to place the unit, or is grading required?)
• Gravel/crushed stone for the pad.
• Heat exchangers to convert energy from the OWB for use in your home.
• Insulated piping from the OWB to your home. (The further the distance the more expensive this cost will be.)
• Excavation costs to bury the insulated piping.
• Hot water storage if the unit will also heat hot water for domestic use (Some manufacturers have this feature built into their design)
• Necessary chimney improvements, including liners.
• Cost for professional installation.

Do your homework before purchasing an OWB, and talk to salespeople with expertise in heating with wood-burning appliances. Always follow manufacturer's instructions for use, cleaning and maintenance of the unit.

More information on OWBs

Outdoor Wood-fired Boilers and Air Quality (N.H. Dept. Environmental Services fact sheet)
U.S. EPA information
EPA information on Best Burn Practices
New Hampshire legislation regulating OWBs

Photo credit: Vermont Department of Environmental Conservation, Air Pollution Control Division. Used with permission