ASHRAE Journal - July 2023 - 29

FIRST PLACE 2023 ASHRAE TECHNOLOGY AWARDS
Energy Efficiency
The first low-energy design decision was to keep
the building floorplate as a simple rectangle located
in the proper solar orientation on the east-west axis.
The window-to-wall-ratio for most of each façade was
carefully designed to allow the appropriate amount of
daylight for the space's function behind each window
and to minimize heat loss and gain (Figure 1).
For example, doctors' offices were intentionally
located predominantly on the south perimeter of the
building, with a window-to-wall-ratio of just 13%,
because that is the minimum window area needed
to use full daylight for each small single-occupancy
office. Electrochromic glazing also was incorporated
for glare control and to further reduce heat gain.
Heat pumps were used for all space cooling,
heating and domestic hot water, further reducing
energy consumption. The LED lighting system has
an installed lighting power density of just 0.52
W/ft2 (5.6 W/m2). The ASHRAE/IESNA Standard
90.1-2007 baseline energy use intensity (EUI) was
67.2 kBtu/ft2·yr (763 MJ/m2·yr) as modeled. The
measured EUI is 36.8 kBtu/ft2·yr (418 MJ/m2·yr)
(including site lighting and two electric car chargers),
resulting in a measured energy savings of 45.2%
compared to the ASHRAE baseline.
Indoor Air Quality and Thermal Comfort
While achieving high level of energy performance,
the building is provided with 30% more outdoor air
than ASHRAE Standard 62.1-2013 requirements and
includes both MERV-13
and electronic final filters.
Thermal variable air
volume (VAV) diffusers
are used throughout
most of the building and
offer exceptional thermal
comfort for this building
type, where spaces like
doctors' offices and exam
rooms have very transient
occupancy.
Because patients visiting
the facility are most often
John Andary, P.E., is a vice president and mechanical engineer at Introba in Oakland, Calif.
J U LY 2023 ashrae.o rg ASHRAE JOURNAL
29
CASE STUDY
feeling ill, having individual temperature control of
each exam room via the VAV diffusers allows those
patients to avoid the additional discomfort of feeling
too hot or cold during examinations.
Innovation
Prior to the design of the Santa Rosa Medical
Office Building 6 project, Kaiser Permanente almost
exclusively used VAV reheat distribution systems
served from packaged rooftop cooling units for all
medical office buildings. Natural gas-fired boilers
would provide space heating (reheat) and domestic
hot water. This design would typically use two coolingonly
DX air-handling units, each serving one half of
the building, delivering approximately 55°F (13°C) air
year-round with reheat at all perimeter zones.
The unique thermodynamically zoned heat pump
(TZHP) strategy provided for the Santa Rosa Medical
Office Building 6 project uses five packaged rooftop
heat pumps zoned by building orientation-north,
east, south, west and core-with each unit serving all
three floors for that orientation. Each heat pump is
a VAV unit that operates in either heating or cooling
mode. This arrangement eliminates reheat in the
building except in unique spaces like corner offices
with more than one orientation.
The TZHP arrangement also allows for an expanded
economizer cycle, resulting in additional energy
efficiency and enhanced indoor air quality. Since
each zone or room supplied by a rooftop heat pump
is experiencing similar heat gain or loss, in the
FIGURE 1 Window wall ratio by orientation and function.
NORTH = 44% WWR
EAST = 30% WWR
SOUTH = 13% WWR
WEST = 12% WWR
HPS

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ASHRAE Journal - July 2023

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