ASHRAE Journal - December 2023 - 51

FIRST PLACE 2023 ASHRAE TECHNOLOGY AWARDS
This project is unique for several reasons, including
a new approach to mechanical design for Arlington
County Parks and Recreation. It features an all-electric
energy-efficient design with a dedicated outdoor
air unit with increased ventilation and enhanced
filtration. Geothermal heat pumps use hot gas reheat
for dehumidification, which supports indoor air quality
metrics while minimizing the building's operational
carbon footprint. Additionally, the building has a solar
microgrid to enhance resilience and reduce additional
operational emissions. Finally, the building was
designed to add square footage and amenities without
removing the existing park space.
Energy Efficiency
Lubber Run leverages several strategies to reduce
energy consumption and electrical demand. They
include a geothermal wellfield with distributed heat
pumps, a dedicated outdoor air system (DOAS) with
energy recovery and demand-control ventilation,
high-performance LED lighting, IT load reductions
and an improved thermal envelope. The wall system
uses mineral wool insulation and a fluid-applied
vapor barrier for reduced embodied carbon and
superior thermal and air leakage performance. The
building's orientation and dramatic overhangs provide
shading to promote daylighting and avoid glare in the
gymnasium and office spaces. The interior lighting
averages 0.45 W/ft2 (4.8 W/m2), a 46% reduction from
ASHRAE/IES Standard 90.1-2013.
Additionally, the community center and
connected parking garage are also designed to be
zero energy. As predicted by energy modeling, the
community center's annual energy consumption is
19.5 kBtu/ft2·yr (221.5 MJ/m2·yr). Likewise, the garage
energy consumption is predicted at 1.3 kBtu/ft2·yr
(14.8 MJ/m2·yr), yielding a combined energy use of
20.8 kBtu/ft2·yr (236.2 MJ/m2·yr) for the community
center and garage footprint.
The county requires future funding for a 300 kW
solar photovoltaic (PV) system that is completely
roof-mounted. Located on a compact site, the design
team collaborated to maintain a south-oriented roof
while minimizing potential PV shading from other
PV panels. Actual energy use data obtained from
CASE STUDY
April 2020-February 2022 indicates an operational
EUI of 22.1 kBtu/ft2·yr (251 MJ/m2·yr) to 22.7 kBtu/ft2·yr
(257.8 MJ/m2·yr) depending on the consecutive months
captured (Figure 1).
The building was occupied while data was collected,
but it was not fully used due to COVID-19. However,
it was one of Arlington County's primary distribution
centers for COVID vaccinations. Since full occupancy
in July 2021, the data is trending to maintain within
1 kBtu/ft2 (11.4 MJ/m2) of the first year of data. As a
result, this community center is on track to set the
new standard for energy use in Arlington community
centers with an EUI of 23 kBtu/ft2·yr (261.2 MJ/m2·yr).
For perspective, the average community center EUI
before this project was more than 90 kBtu/ft2·yr
(1022 MJ/m2·yr).
Indoor Air Quality and Thermal Comfort
The building's outdoor air is decoupled from heat
pump units that provide heating and cooling to the
space. Heat pumps with hot gas reheat are incorporated
in areas with high activity and latent loads to ensure
humidity is maintained below 55% relative humidity.
The ventilation is accomplished via a single dedicated
outdoor air unit (DOAS) with variable airflow capacity.
Demand-control ventilation is based on CO2 levels and
occupancy sensors. The spaces have a CO2 setpoint of
800 ppm with maximum airflow to the space at 30%
greater than ASHRAE Standard 62.1-2016.
The DOAS has MERV 8 and MERV 13 filters, and the
heat pumps have a 2 in. (51 mm) filter rack capable
of using a MERV 13 pleated filter. The local building
automation system collects the CO2 sensing results and
monitors them to signal an alarm when spaces reach
high CO2 levels. As research continues to evolve on the
effect of indoor air quality and occupant performance,
the system's setpoints can be changed to accurately
reflect best practices. High-volume/low-velocity fans
contribute to thermal comfort in the gymnasium
allowing a 2°F (1°C) rise in temperature setpoint when
operating. Spaces are served in a manner that allows the
beauty of the overhead construction materials to shine.
Innovation
The building is 100% electric, and to avoid on-site
Lee Harrelson, P.E., is a principal/senior mechanical engineer, Tracy Steward is a partner/mechanical engineer, Dennis Finn, P.E., is a mechanical engineer and Brian Turner, P.E., is an electrical
engineer at CMTA.
D ECEMBER 2 0 2 3
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