Outdoor hydronic heaters (wood-fired boilers) are typically located in small, insulated sheds that burn wood to heat water, which is then piped underground to provide heat and hot water to occupied buildings.
Outdoor wood-fired boilers can be more polluting and less efficient than other home heating technologies. Research by the State of New York has found that even when used properly, one of these units can emit as much fine particle pollution as:
- 12 EPA-certified indoor wood stoves
- 1,000 homes with oil heat
- 1,800 homes with natural gas heat
Improperly located and operated outdoor wood-fired boilers create heavy smoke and release it close to the ground, where it lingers and can expose everyone in the area to nuisance conditions and health risks.
These units are designed to burn dry, seasoned wood.Using them to burn green wood generates much more smoke.
Under the MassDEP Wood-Fired Boiler Regulation (see below):
- Only units that meet EPA emission standards and whose manufacturers have filed compliance certifications may be sold for installation in Massachusetts.
- New units must be located minimum distances away from property lines and neighbors' dwellings.
- All units need to meet minimum smokestack height requirements, burn only clean seasoned wood, and cause no nuisances or conditions of air pollution.
The regulation authorizes towns and cities - through their building, health, police, and fire departments - to enforce specific provisions. Some municipalities have enacted by-laws or ordinances that prohibit or limit the use of outdoor wood-fired boilers.
MassDEP and local boards of health can take enforcement actions in cases of excessive odor or smoke. Sometimes the only way to resolve complaints is for the owner of a unit to stop using it permanently.
If you are thinking about buying an outdoor wood-fired boiler:
- Confirm that it is legal to install and operate one in your community,
- Ask local officials about any specific restrictions you need to know about, and
- Consider the impacts an outdoor wood-fired boiler could have on your neighbors and their property
If you do purchase a unit, never use it to burn anything other than dry firewood, and to the extent you can, operate it only during the cold weather months.