Concentration of CO2 in the Atmosphere

Dry Wood Chip Boiler Heats 104-Unit Housing Complex

The new 1.84 million BTU/hr Viessmann Vitoflex 300-RF biomass boiler. Photos courtesy of Froling Energy.

By Jim Van Valkenburgh

Applegate Apartments in Bennington, Vermont is among the largest affordable housing developments in the state. Heat and hot water have always been provided in each unit as part of the rent, which is a nice benefit for tenants. But in recent years, annual fuel costs had risen to over $175,000 per year. Housing Vermont, Shires Housing and Applegate Housing Inc. put their heads together to make Applegate more sustainable, financially and environmentally.

In 2017, the 104 units at Applegate Apartments got new windows, insulation, roofing, siding and a new central biomass-fired district heating system which together reduced the 19-year-old complex’s annual heating costs by over 50%.

Newly buried insulated pipes carrying biomass-heated hot water now run throughout the complex, connecting all 23 buildings to a new central boiler house. This change eliminated 23 separate oil boilers which were burning over 50,000 gallons of oil each year for heat and hot water.

Eric Schmitt of Housing Vermont described the project. “Comparing the new system’s first year energy costs to the previous two years (2013-2015), when the complex had 23 individual oil boilers, the complex saw energy costs drop from an average of $169,000 to a first-year cost for dry wood chip fuel and propane of $49,668. This incredible reduction can be attributed to a combination of the fuel switch to dry wood chips and the many energy saving upgrades that were made to every building in the complex.”

Froling Energy installed the new Viessmann Vitoflex 300-RF dry wood chip boiler and storage silo that is at the center of the new system. Froling also supplies the 25% moisture content screened wood chips into the silo with their blower truck which pushes the chips into the 25-foot-tall silo through a five-inch diameter pipe. Their dry chips and the blower truck delivery method are innovations that greatly reduced the typical initial cost of a wood chip boiler system. With semi-dry wood chips, the Viessmann boiler meets all Vermont emissions requirements without expensive scrubbers or ESPs (electrostatic precipitators). Future maintenance costs will also be less than they paid for maintaining the many old oil boilers each year.

Schmitt went on to tell about “value engineering” that helped to contain costs of the biomass boiler system. “Using our energy modeling software and working with Froling Energy, we right sized the biomass boiler from the original design at 3.2 million BTU/hour peak output (MMBTU) to 1.8 million BTU/hour. This one change saved $200,000 in construction costs. This was a very safe change because our modeling showed that even when outdoor temperatures were at -10°F, the downsized system was still only running at 75% of maximum capacity.” A new propane boiler was also installed for back-up and to cover peak load situations.

Blower Truck filling the 42-ton dry wood chip silo at Applegate Housing.

Housing Vermont continues to keep track of the new boiler system’s performance at Applegate. Schmitt commented, “Our software gives us real time insight into the current operation of the new system with data about the operation and output of the biomass boiler and details like whether the propane back-up boiler is running when the biomass should be. So far, we confirm that all boilers have been running effectively.”

The Applegate Energy Rehab project has been a big win for everyone involved: Shires Housing who manages the property, Naylor & Breen Construction the project general contractor, Goldstone Architecture, WV Engineering, Froling Energy and others. Funding for the project came from a variety of sources including Housing Vermont, Efficiency Vermont, the Vermont Clean Energy Development Fund, Vermont Housing and Conservation Board, HUD and the Vermont Community Development Program.

Froling Energy, based in Peterborough, New Hampshire, specializes in installation of commercial biomass boiler systems in New England. Its recently completed projects include wood chip boiler systems installed at the Merrimack County Jail complex in Boscawen, NH, at Whelen Engineering’s manufacturing campus in Charlestown, NH and at Plymouth (NH) Regional High School.

Jim Van Valkenburgh is VP Sales & Marketing for Froling Energy. He can be reached at 603-924-1001 x2. For more information on Froling Energy go to

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