Outdoor Wood-Fired Boilers
Rising fuel costs have made heating a home or business a very expensive proposition. To face this challenge,
some in Montgomery County have turned to an old-fashioned idea enhanced by new technology—outdoor
wood-fired boilers (OWB). While this term may not seem familiar, it is the formal name for outdoor
wood-burning furnaces or outdoor hydronic heaters. This technology has been used for hundreds of
years and is becoming more popular as people look for alternative ways to heat buildings. This can be an
effective, cost-saving method, but it also creates a number of environmental and health concerns.
The Technology
An OWB consists of a small shed housing a firebox with a smokestack located outside of a building. The
firebox burns wood and/or other biofuels, such as corn, and heats a liquid, usually water or an antifreeze
mixture, which is then piped into the building. The heated liquid is used to heat the building and/or the
hot water supply.
An outdoor wood-fired boiler in Montgomery County.
Benefits and Considerations.
Savings. Savings can vary widely based on the size of the building,
original heating system, availability and cost of fuel, and the efficiency
of the system. Manufacturers claim that heating costs can be reduced
by 30 to almost 100 percent.
Cost. Prices for the units will vary, but most are about $5,000. This does
not include installation costs.
Renewable Resource. If managed correctly, wood and biomass fuels
are renewable resources.
Indoor Air Quality. OWBs can eliminate indoor air quality issues by
eliminating the use of an indoor fireplace or wood stove.
Pollution. The smoke created by the OWB contains high particulate
emissions that can cause serious health and environmental damage.
This can be even more damaging if the unit is not efficient or is burning
improper materials.
Nuisance. Smoke produced by the OWB can pose a nuisance if it affects
other properties. To prevent this, a certain chimney height should
be required.
Fire Risk. Quality construction standards, proper installation, and correct
siting should be ensured to reduce fire risk. With proper construction
and use, an OWB has little chance of being a fire hazard.
Pictures of inefficient outdoor wood-fired boiler in use.
Ash Disposal. The use of an OWB creates a substantial amount of ash
which should be reused or disposed of in a proper manner.
Maintenance. To ensure the efficiency and safety of a unit, regular
maintenance is required. This includes shoveling out ash every couple
of days, adding water lost during evaporation, and cleaning the water
Illustration of a complete outdoor wood-fired boiler system.
50’
50’
filter. Most boilers come with a 20-year limited warranty.
Regulatory Considerations
The Pennsylvania DEP has finalized a rulemaking that amends
Pa. Code Chapters 121 and 123 relating to the protection of air
resources through the regulation of OWBs. The final approval of
this rulemaking has been published in the Pennsylvania Bulletin
(Volume 40, Number 40 October 2, 2010). Municipalities that
have already enacted OWB ordinances must be aware that this
rulemaking preempts their regulations; though municipalities
can enact ordinances that are more strict. The following is a
brief summary of the final rulemaking:
Illustration depicting the required property line setbacks
•
The final-form rulemaking does not apply to existing OWBs
and those sold during the phase-in period.
•
The OWB must be EPA Phase 2 qualified.
•
The OWB must be installed at least 50 feet from the nearest
property line.
•
The OWB must have a permanently attached stack. The
stack must extend a minimum of 10 feet above the ground
and be installed to the manufacturer’s specifications.
•
The OWB must use only regulation approved fuels.
•
The OWB must comply with all other applicable state,
county, and local laws and regulations.
These are just a brief description of the key points in the
rulemaking and we recommend that the whole regulation
is read.
Example of an EPA Phase 2 Qualified tag.
An outdoor wood-fired boiler and wood pile in Montgomery County.
An outdoor wood-fired boiler.
Courtesy of Steve Galle.
For more information, please contact the Montgomery County
Planning Commission at 610.278.3722 or visit our site online at
www.planning.montcopa.org to see the complete renewable
energy series and other resources.
Printed on recycled paper
Printed in 2011
Montgomery County Planning Commission
Montgomery County Court House
PO Box 311, Norristown, Pennsylvania 19404
website: www.planning.montcopa.org