Centerbrook has designed a new Central Heating Facility for The Hotchkiss School in Lakeville, Connecticut that heats the campus by burning woodchips. It replaced an oil-fired boiler, and is expected to reduce greenhouse gas emissions by a third to nearly a half. The new 16,500-square-foot building houses two biomass boilers; four truck bays feed wood chips into a 17,500-cubic-foot storage bin capable of supplying a week’s worth of fuel. An oil-fired boiler serves as backup or for use on milder days.
The Facility is part of the high school’s commitment to becoming a carbon-neutral campus by 2020. Hotchkiss is an independent boarding school with 600 students from across the United States and abroad.
The two Messersmith boiler units, which operate at 80 to 82 percent efficiency, can generate 20 million BTUs per hour burning waste wood acquired from sustainably harvested local forests that are certified by the Forest Stewardship Council. The woodchips replace some 150,000 gallons of fuel oil per year and cut emissions overall, most dramatically sulfur dioxide by more than 90 percent. Waste ash from combustion is collected for use as fertilizer for the school’s vegetable gardens, and an electrostatic precipitator removes 95 percent of particulate matter from emissions. The 48-foot chimney disperses emissions into the prevailing winds, reducing ground-level impacts to nearly zero.
Woodchips collected from managed timber stands are considered a “carbon neutral” fuel by the International Panel on Climate Change because the CO2 produced by their use is reabsorbed by the ecosystem through replanting and regrowth of the forests where they originate. Biomass heating is expected to reduce Hotchkiss’ carbon footprint by more than 6 million pounds of CO2 a year. There are currently 80 biomass facilities in 20 states.
In order to merge with the surrounding landscape, the new building has a low profile and an undulating, sloped green roof. The Facility is one of only three LEED certified power plants in the country. Sustainable features include: the building’s vegetated roof of hearty sedums that will combine with a bio-swale/rain garden system to absorb rainwater and filter runoff before returning it to the ground; a renewable, laminated wood structural system; water-conserving plumbing fixtures; use of local materials with a high recycled content; an abundance of daylight; and highly efficient mechanical systems, lighting systems, and exterior skin.
The building also serves an educational mission, exposing its technologies and wood structure to tours by students and community groups, who have access to a mezzanine balcony that overlooks and circumnavigates the boiler room. In addition, wall-mounted charts and maps and a series of interactive computer consoles that track performance data are on display. Outside the plant, visitors can follow a nature path that affords up-close views of the green roof and meanders through the newly created rain gardens, bio-swales and nearby wetlands.
“Our goal for this project is to build upon a philosophy that further connects students to the natural resources they use daily,” said Josh Hahn, assistant head of school and director of environmental initiatives. “Our farm connects students to their food systems, and the Central Heating Facility will connect students to their energy systems. We know that energy, and environmental issues in general will be front and center as our students enter their adult lives. This building, built as a classroom, will prepare them to make creative and intelligent choices in a world with ecological limits.”
Photography © David Sundberg/Esto