ASHRAE Journal - August 2023 - 55

HONORABLE MENTION 2023 ASHRAE TECHNOLOGY AWARDS
Energy Efficiency
The MHP Wellness Center and YMCA are compliant
with ASHRAE Standard 90.1-2007 as verified with
COMcheck software version 4.1.2.0. After collecting one
year of energy data, the facility performed at an EUI of
76.9 kBtu/ft2·yr (873.3 MJ/m2·yr).
Using simulation software, a baseline energy model
following ASHRAE Standard 90.1-2013 Appendix
G indicates a performance of 96.1 kBtu/ft2·yr
(1091 MJ/m2·yr). However, the Wellness Center and
YMCA improve upon the minimum performance by
about 20%. Most of this energy reduction comes from
the heating end-use where energy recovery of ventilation
air and better performing mechanical systems
reduce the building's heating requirements.
To reduce energy consumption by minimizing envelope
heat gain and infiltration, the design team implemented
a well-insulated, airtight wall construction
using stud framing with rigid foam insulation and liquid
applied vapor membrane. Excluding the pool area,
the mechanical design consists of a 56-well geothermal
heating and cooling system with centralized pumping
and distributed vertical water-source heat pumps
located in closets. Ventilation is handled by a decoupled
dedicated packaged outdoor air unit with indirect gas
heat, energy recovery and digital scroll compressors.
The pool area is conditioned with an indoor dehumidification
unit paired with a remote, air-cooled fluid
cooler and gas furnace to provide stable room conditions
with peak energy efficiency. A dedicated, high-efficiency
gas-fired boiler heats the pool at its initial fill or when
drained and refilled. When heating is required during
regular operation, the dehumidification unit's integral
heat exchanger rejects heat to increase the pool water
temperature. Free heat rejection from the pool unit lowers
the energy used to keep the pool temperature comfortable.
A regenerative filter reduces water consumption
by eliminating backwash water use.
After the facility began full operation, the design team
continued to work closely with MHP facility operators
to collect energy data to optimize the building's performance.
For example, a specific focus was placed on
optimizing the pool unit's heat recovery component to
reduce the pool boiler's gas consumption of the pool
boiler. The first six months of operation, projected
CASE STUDY
over a full year, yields an EUI of 81.8 kBtu/ft2·yr
(929 MJ/m2·yr), while the last six months of operation,
projected over a full year, yields an EUI of
73.6 kBtu/ft2·yr (836 MJ/m2·yr).
Indoor Air Quality and Thermal Comfort
Building occupancy wellness requires high-quality
indoor air, and to achieve ASHRAE Standard 62.1-2010
requirements, a dedicated outdoor air system (DOAS)
decoupled from the geothermal heating and cooling system
serves the facility, minus the pool area. The DOAS
consists of a single roof-mounted packaged air handler
with hot gas reheat and modulating gas heat. Variable
air volume (VAV) boxes are used to serve zoned spaces.
The DOAS has variable flow capability with demand
control ventilation (DCV). VAV boxes ducted directly to
the space they serve are interlocked with a space occupancy
sensor and modulate based on the measured
indoor and outdoor CO2 levels. The BAS measures
CO2 in the space and maintains a CO2 differential of
700 ppm between the indoor and baseline outdoor
measurement. Data collected after a year of operation
shows occupied spaces such as the gym and daycare
facility have a CO2 differential of less than 200 ppm,
creating healthy spaces for occupants. A differential
this low would earn points under the International Well
Building Standard v2.
Moisture given off by a person can increase the latent
load in the space and raise the relative humidity, making
the space feel uncomfortable and sticky. To combat
this effect, two design elements were incorporated:
decoupling the ventilation from the heating and cooling
system and using a dehumidification sequence that
keeps spaces below 55% RH, granting greater control of
space humidity. Additionally, select terminal heat pump
units were equipped with hot gas reheat coils to allow
space dehumidification, particularly in large spaces
with intermittent occupancy loads.
The pool area is ventilated via the dehumidification
unit and a roof-mounted exhaust fan. The minimum
required outdoor air is mixed into the return airstream
and delivered from the dehumidification unit high
in the space, while exhaust and return are strategically
located low in the space. The high supply and low
return/exhaust paired with several destratification fans
Doug Fick, P.E., is project manager/senior mechanical engineer at CMTA in Indianapolis, Ind. Liz Alford is mechanical engineer, Jeremy Lewis is a partner/electrical engineer, and Doug Hundley, P.E., is vice
president/mechanical engineer at CMTA in Louisville, Ky.
A U G UST 2023 ashrae.o rg ASHRAE JOURNAL
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