November 4, 2013

Is outdoor wood boiler up to code?

From staff reports

---- — Indiana has specific rules about how outdoor wood heaters can be used and what can be burned as fuel.

While the majority of Hoosiers heat their homes with natural gas, an electric furnace, or even an indoor wood stove, some use outdoor wood boilers to produce heat. Outdoor hydronic heaters (also called outdoor wood boilers or outdoor wood furnaces) are free-standing wood-burning appliances that heat water, which is then pumped to one or more structures to provide heat. An outdoor hydronic heater also can be used to provide hot water year-round to structures and to heat swimming pools. Units are typically the size and shape of a small storage shed or mini-barn with a short smoke stack on top. They are much larger and differ in design, operation, and emissions produced from the smaller indoor wood stoves, pellet stoves, and fireplaces.

Since 2011, the Indiana Department of Environmental Management has implemented rules that govern the use of outdoor hydronic heaters, in addition to the federal rules that govern them. You can view the full language of rule 326 IAC 4-3 in the Indiana administrative code. Find more information on outdoor hydronic heaters and their restrictions at

Units that were made prior to U.S. EPA’s Phase 2 emission rules can only operate from Oct. 1 through April 30 in Indiana. Newer, Phase 2 certified models can operate year-round. All units in the state must follow these basic regulations:

1) Units must burn clean wood or other approved renewable fuel.

2) Smoke from the stack is limited to less than 20-percent opacity (the amount of light blocked by particulates). Good combustion practices and proper maintenance of the unit should lead to compliance with the 20-percent limit.

3) Units must abide by all federal, state and local ordinances.

4) Outdoor hydronic heaters that have not been qualified to meet U.S. EPA’s Phase 2 emission limits must have a permanent stack extending 5 feet higher than the peak of the roof of any occupied building within 150 feet of the unit.

Only outdoor hydronic heaters that meet Phase 2 standards can be distributed, sold, or installed in the state. When purchasing a new unit, look for a white tag affixed to the unit, which signified it meets the Phase 2 emission limits. Sellers and dealers must provide a copy of the rule (326 IAC 4-3) to buyers, and the buyer must sign a notice confirming receipt of the rule. The seller or dealer must send the signed notice to IDEM within seven days of delivering the unit to the buyer or lessee.