Affordable, environmentally friendly outdoor furnaces

The Basics

Outdoor furnaces (also called “hydronic heaters,” “stoves” or “boilers”) utilize advanced technologies for an age-old idea: Burn wood, corn or other agricultural materials and other renewable sources to generate heat. These sources are:

  • Renewable resources
    • Restored and replenished by nature in time compatible with human use
    • Carbon neutral, which means no net increase in greenhouse gas emissions. Other heat sources (coal-generated electricity, natural gas, fuel oil, kerosene) are being depleted at rates much faster than the time it took to create
  • Clean
    • Burning any fuel produces carbon dioxide, the primary greenhouse gas
    • Wood is part of natural carbon/carbon dioxide cycle
    • No net increase in carbon dioxide emissions
  • Affordable
    • Lower heating bills
    • More control
  • Reliable
    • “On” during power outages/rolling blackouts
  • Energy independent
    • Allows people to get off the grid in “civilized” manner

Outdoor Furnace Best Burn Practices

It is important to install and operate outdoor furnaces properly and according to manufacturer recommendations and follow these best burn practices:

  1. FUEL USED: Onlyuse listed fuels recommended by the manufacturer of your unit. Never use the following: trash, plastics, gasoline, rubber, naphtha, household garbage, material treated with petroleum products (particle board, railroad ties and pressure treated wood), leaves, paper products, and cardboard.
  2. LOADING FUEL: For a more efficient burn, pay careful attention to loading times and amounts. Follow the manufacturer’s written instructions for recommended loading times and amounts.
  3. STARTERS: Do not use lighter fluids, gasoline or chemicals.
  4. LOCATION: It is recommended that the unit be located with due consideration to the prevailing wind direction.
  5. Always remember to comply with all applicable state and local codes.

Provided by the Hearth, Patio and Barbecue Association (HPBA), Outdoor Furnaces Manufacturers Caucus

EPA Testing

The U.S. EPA conducts testing on outdoor furnaces, measuring particulate matter (PM). EPA reports include these findings:

“The EPA hydronic heaters program encourages manufacturers to improve air quality through developing and distributing cleaner, more efficient hydronic heaters. This program will achieve emission reductions and protect public health sooner than a federal rule.” More

Lists of cleaner burning hydronic heaters that qualify for the EPA voluntary program.

Emissions regulations for your area.

“Compared to a wide range of residential heating options, these furnaces’ emissions were of the same order as other stick wood burning appliances.” See the report. PDF


“New emissions test data and future trends,” Peter Guldberg’s paper presented to the Annual International Emission Inventory Conference, May 2007. Read this report. PDF