ASHRAE Journal - November 2021 - 55

HONORABLE MENTION | 2021 ASHRAE TECHNOLOGY AWARD CASE STUDIES
Energy Effi ciency
FIGURE 2 Massachusetts Hall EUI comparison.
The existing MEP systems did not provide a comfortable
or energy-effi cient environment for Harvard's
senior administration. The constant volume HVAC systems
were too noisy within the executive board room
and other offi ces. As a result, spaces required excessive
precooling before meetings began. Then, the systems
were shut off entirely. This process, coupled with the
aged systems, translated into an ineffi cient building
with an energy use intensity (EUI) of 125.3 kBtu/ft2·yr
(1423 MJ/m2·yr). With the use of new high-performance
air-handling systems equipped with variable frequency
drives (VFDs), variable air volume (VAV) terminal boxes,
fan coil units equipped with electronically commutated
(EC) motors, hot water pumps with VFDs and a more
sophisticated energy management system, Harvard
was able to reduce the energy consumption to an EUI of
93.5 kBtu/ft2·yr (1062 MJ/m2·yr).
This renovation project complied with the current
Massachusetts State Building Code at the time
of design (late 2017/early 2018), which references
ASHRAE Standard 90.1-2013 and International Energy
Conservation Code 2015.
Indoor Air Quality
Before this upgrade, fresh air for this building was
designed to be brought in largely through windows
via natural ventilation. While this met code according
to ASHRAE Standard 62.1-2013's Ventilation Rate
Procedure, the approach was impractical given the
nature of the space use with occupants requiring quiet
and many times private work environments. The ventilation
upgrade included mechanical ventilation for
all offi ce spaces, through either central mixed air handlers
or dedicated outdoor air handlers that ducted
conditioned 100% outdoor air into areas where all air
systems were not spatially practical. For increased comfort,
higher occupancy areas like conference rooms
were equipped with CO2 controls, which communicate
with the central mixed air-handling units in real-time
to boost the outdoor air quantity to manage CO2 levels
continuously.
Innovation
A major challenge was the requirement to maintain
the historical and architectural beauty of the building.
Constraints to the design included low fl oor-to-fl oor
400,000
350,000
300,000
250,000
200,000
150,000
100,000
50,000
Energy Use
2017
2019
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
height of 7 ft, 2 in. (2.2 m) in the basement mechanical
space, limited plenum space to route services, drywall
ceilings throughout, and no changes to the internal or
external aesthetics were allowed. Additionally, given
the historic signifi cance of the building, all work was
reviewed by the Cambridge Historical Commission.
Collectively, this required the design team to develop
a unique and innovative design approach to meet the
modern standards of comfort. A low velocity, high-performance
VAV air-handling system that relied on perimeter
vertical supply ducts that were concealed within
the existing wall pilaster cavities and millwork was
developed. Dual air handlers and VAV boxes, all located
in the basement for easy access and maintenance, are
connected to the perimeter supply air risers to serve the
fi rst and second fl oors.
Operation & Maintenance
The design of the HVAC system included providing
system redundancies to minimize energy use and equipment
degradation. Air-handling unit fans and coils were
sized with 2/3 redundancy. The supply and return duct
mains from both units were headered together, and
the units operate in parallel at a reduced speed. The
hot water heat exchangers and pumps were sized with
full redundancy. The heat exchangers and pumps are
headered together and operate in a lead-lag manner to
share operating time. This redundancy will help maintain
continuous operation and minimize shutdowns
throughout the year. The design also considered how
future maintenance would be performed. To allow for
maintenance with the least disruption, for example, VAV
boxes serving fi rst- and second-fl oor executive offi ces
were located in the basement where they can be serviced
and repaired without requiring personnel to enter occupied
spaces.
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ASHRAE Journal - November 2021

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