Hotchkiss School Central Heating Facility


Delivery method
16,500.0 SQ FT


The Hotchkiss School in Lakeville, Connecticut built a new 16,500 square foot Central Heating
Facility (CHF) replacing oil-fired boilers with wood chip burning boilers and reducing greenhouse
gas emissions by one third, which is one of only three LEED certified in the country. The
laminated wood structure is low profile with an undulating, sloped vegetated roof. The building
will serve as an educational tool designed for student as well as community tours to highlight the
energy technology. The new CHF houses two biomass boilers that can generate 14 million
BTU's per hour, in the form of 60 psi steam and heat the entire campus, which houses 600
students in grades 9 thru 12 and has 20 dormitory and classroom buildings. A 400 horsepower,
13.8 million BTU per hour oil fired steam boiler was installed for backup. Wood chips acquired
from local forests will replace 150,000 gallons of fuel oil per year and reduce the sulfur dioxide
emissions by at least ninety percent. The biomass heating is expected to reduce Hotchkiss'
carbon footprint by more than 6 million pounds of CO2 a year also. The waste ash from
combustion will be collected for fertilizer and an electrostatic precipitator will remove over 95%
of particulates from emissions.

Modern Mechanical Systems, Inc. was awarded the plumbing and mechanical work for the CHF
project, including 3300 feet of underground steam and condensate distribution piping serving
the campus and 3850 feet of underground hot water piping serving the Mars Athletic Center and
the Maintenance Garage. The project was a $2.7 million contract constructed from mid-July of
2011 through September of 2012. There were 14,500 mechanical hours expended to complete
the project and 71% were self-performed by Modern Mechanical Systems, Inc.

The mechanical scope of work included installation of a steam boiler, deaerator, blowdown tank
and associated high pressure steam and condensate piping, pressure reducing station,
feedwater and blowdown systems. A 15,000 gallon underground fuel oil tank with a duplex
pumping and filtration system were installed to fuel the backup boiler. Piping of the two biomass
boilers was also included in the work. Hot water and hot glycol supply and return was
accomplished through the use of high efficiency steam-to-liquid vertical flooded heat
exchangers, and circulated through the piping system using a pair of pumps controlled by
variable frequency drives. All large bore piping was required to be welded, and a rigorous
system flushing and testing procedure was required.

The CHP's maintenance shop is heated by a radiant in floor piping system fed from the glycol
system, and has unit heaters as a secondary system. The building also has a maintenance
office incorporating a full staff bathroom and kitchenette using water conserving plumbing
fixtures. Emergency eyewash stations and showers are installed in the Boiler Room and the
Maintenance Shop.