ASHRAE Journal - September 2023 - 57

SECOND PLACE
2023 ASHRAE TECHNOLOGY AWARDS CASE STUDY
Energy Efficiency
The renovation portion of the project was permitted
under the 2015 Seattle Energy Code as a substantial
alteration in two phases using the C407 Total Building
Performance Path. The original 1997 building envelope
featured dual-paned windows, a steam-based central
heating plant, a chilled water plant and laboratory
systems for air distribution and space conditioning. The
renovation reused much of the original architectural
and central utility plant frameworks but replaced,
enhanced and added envelope and MEP systems as
needed to meet the new building programming and
project performance goals. Three key energy-efficient
HVAC design strategies include:
1. High-Efficiency Central Utility Plant With Heat
Recovery. The upgraded campus central utility plant
supplies chilled water (CHW) and heating water (HW)
via a primary-secondary configuration to hydronic coils
across the campus. The existing steam boiler plant was
removed and replaced with a mix of air-to-water heat
pumps, heat recovery chillers and high-efficiency gasfired
condensing boilers. Chilled water is provided by
two existing upgraded chillers and a newly added third
chiller. Cooling towers were refurbished to minimize
water use and chemical requirements. Energy efficiency
and carbon reduction are prioritized by maximizing
the operation of the heat recovery chiller to provide
simultaneous heating and cooling when possible.
As a technology company, owner requirements
for main distribution frame (MDF), intermediate
distribution frame (IDF) and uninterruptible power
supply (UPS) rooms provide abundant consistent
sources of heat that can be recycled and repurposed
for space heating. A key energy conservation measure
(ECM) for the project is using heat recovered from
these rooms for space heating. The IT and electrical
room spaces are served by dedicated constant air
volume (CAV) air-handling units (AHUs) provided with
a cooling coil that absorbs heat generated from the IT
and electrical rooms. This heat is then transferred to
the heating water system via the heat recovery chillers.
These AHUs are also provided with full outdoor air
economizer capability to allow " free cooling " when
outdoor conditions are favorable and heating demand
at the campus level is low. The units provide a supply
air temperature of 65°F (18°C) to allow for higher heat
quality for recovery and increased economizer hours.
2. High-Performance VAV Systems. Regularly
occupied spaces (offices, conference rooms, corridors
and congregation spaces) in the renovated buildings are
served by CHW and HW variable air volume (VAV) airhandling
units (AHUs) connected to HW heating parallel
fan-powered terminal boxes at the perimeter and single
duct terminal boxes at interior zones. The VAV systems
provide ventilation, sensible and latent cooling and
heating for morning warm-up conditions. Relief air
AHUs include coils to recover heat from relief air. All
AHUs are in the mechanical penthouses and distribute
medium pressure supply air through ductwork in
vertical shafts to each floor plate. Low pressure return
air ductwork transfers return air from office floors into
a general construction shaft to return air back to the
penthouse. Terminal units feature ECM-driven fans,
and interior terminal units are selected to maintain
full cooling at the maximum AHU reset temperature
(60°F [16°C]). For highly glazed areas in the central
" Commons " area, in-floor hydronic radiant systems are
provided to handle a portion of the perimeter load for
both heating and cooling.
3. Focus on Energy Conservation and Carbon
Through Modeling. Energy modeling software
informed and was relied upon for design strategy
selection, energy code compliance and LEED v4
certification. The proposed design exceeds the 2015
Seattle Energy Code requirements by 5.6% and the
Standard 90.1-2010 LEED v4 baseline by 37%. The Seattle
Benchmarking site has energy use data for the campus
pre- and post-renovation. Prior to renovations, the
biotech laboratory-based campus had a 2015 site energy
use intensity (EUI) of 206 kBtu/ft2·yr (2339 MJ/m2·yr).
This 2015 data set indicates that 49% of the energy
consumed was electricity, while the remaining 51% was
natural gas use. Using the emissions factor for electricity
from Seattle City Light 2014 (20.08 lb CO2/MWh) and
the emissions factor for gas from Energy Star Portfolio
Manager (53.11 kg CO2/MBtu), pre-renovation emissions
were 4,830 MT of CO2e with 89% from natural gas.
Post-renovation, the repurposed tech office
Expedia campus performed at an EUI of 40.5 kBtu/ft2
(460 MJ/m2) in 2020. That same year 88% of the energy
Dave Budd, P.E. is senior mechanical engineer, Caroline Traube, P.E., BEMP, is engineering manager, building performance, Michael Hedrick is engineering manager, and Skander Spies, P.E., is senior
mechanical engineer at McKinstry.
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