Please Keep Vermont Green: Burn Clean!

Welcome to the Vermont Department of Environmental Conservation website on Outdoor Wood Boilers (OWBs) or Outdoor Wood Hydronic Heaters (OWHH). With the high cost of heating oil, more Vermonters are looking to wood as a source of heat and hot water, but not all wood heat is the same. While indoor wood stoves have been tested and certified by EPA for emissions since 1990, testing and certification of more efficient outdoor wood boilers has only recently begun. Old style OWBs cause dense smoke and many are equipped with very short smoke stacks so the smoke does not disperse well. This smoke endangers the health of you, your family and neighbors as well as the environment. The newer certified “Phase II” OWBs are a great improvement.

The claims from some OWB manufacturers about old style OWBs did not prove to be accurate with time and testing. We want you to have the facts before making an investment. OWBs are regulated in VT and may also be regulated or banned by your town. This site is designed to help you get the facts. If you have any questions about OWBs, please contact us.

The Vermont Department of Environmental Conservation is engaged in an outdoor boiler changeout effort. For details on eligibility and application forms, please visit:



OWB Certification Application Form (PDF)