Should local governments regulate outdoor wood boilers? – Part 2

Although popular and cost-effective, many outdoor wood boilers produce a lot of smoke, creating potential health risks and nuisance complaints. Local governments can reduce that risk though zoning standards.

As outdoor wood boiler home heating systems become more popular, community leaders may receive complaints from neighbors about smoke from these units. Local governments can apply zoning standards to reduce the impact of these systems under their authority to protect public health, safety and welfare.

The first step for local leaders is to determine to what extent outdoor wood boilers are a current or potential issue. Even in the absence of complaints, if more of these systems are being installed in your community, it may be worth establishing standards now to prevent future issues.

Outdoor wood boilers are similar to other accessory uses on a property, and can be subject to setback, screening, construction and other standards. Possible standards for these systems may include:

  • Setbacks – Conventional outdoor wood boilers are very smoky, and studies show that unhealthy concentrations can extend many hundreds of feet from the unit. For these conventional units, large setbacks from property lines, 500 to 1,000 feet or more, might be needed to reduce impacts on neighbors. On the other hand, newer Environmental Protection Agency (EPA) Phase 2 Qualified systems, produce much less smoke, so setbacks for those units could be reduced to the same distance as other accessory structures. Larger setbacks only indirectly address the issue, helping to reduce health and nuisance impact to neighbors, but not remedying potential concerns near the home where the boiler is located.
  • Smoke stack height – Smoke stacks on conventional wood boilers may be very short, as low as five or six feet from the ground. Smoke from short stacks may drift closer to the ground where it is more likely to be inhaled. Zoning standards could require minimum stack heights, for example, five feet higher than any structure within 500 feet, with an absolute minimum of at least 15 feet.
  • Zoning district restrictions – Since higher housing density creates a greater chance for impacts from wood boiler smoke, zoning could limit conventional systems as a permitted use to certain districts with low housing densities, such as agriculture/forest. High efficiency units could be a permitted use in additional low-density residential districts if there are appropriate areas for wood storage. Outright prohibition in selected districts should be considered only if there are no feasible solutions that would address smoke and safety concerns.
  • Construction standards – To help ensure safety, zoning standards could include requirements that permitted wood boilers meet appropriate independent safety standards such as UL, CAN/CSA, ANSI or others.

Outdoor wood boilers are designed to burn logs and split wood, not other materials. Local ordinances could list prohibited materials such as garbage, treated wood, plastic, and lawn clippings. This type of restriction might be best addressed and more easily enforced in a separate outdoor burning ordinance, rather than through zoning provisions.

The Michigan Department of Environmental Quality (DEQ) Model Open Burning Ordinance includes outdoor wood boiler provisions that would be appropriate in a zoning ordinance. The DEQ Woodburning and Air Quality website provides links to other sample regulations.

For additional information about other energy issues in planning and zoning, see the Michigan State University Extension land use website.

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