Hospitals can reduce energy use with the
aim of achieving net-zero energy (NZE).
Insights from hospitals that are on the path
to NZE and other buildings that have real-
ized this goal help identify barriers and help
identify next steps for the healthcare sector
to design-toward and achieve NZE.
Keywords: Hospital, Healthcare, Energy
Efficiency, Net Zero Energy
Abstract
In the United States hospitals use nearly 4% of national
energy, emit over 8% of U.S. commercial building
greenhouse gas emissions, and exceed $9 billion in
annual energy costs. Recognizing buildings’ impacts
on atmospheric health as well as their connection to
community health and economic viability, more hospi-
tals are evaluating their energy impacts. Concurrent
efforts are being made to improve codes, strengthen
standards, and accelerate deeper energy savings across
the building sector. This paper will explore how hospi-
tals can reduce energy use with the aim of achieving
net-zero energy (NZE). First, it will contextualize
hospital energy use in the U.S., discussing common
design practice, and define the scope and scale of NZE
for commercial building projects. It will then highlight
programs such as Targeting 100! and case study examples
of forward-thinking hospitals that are leaders in deep
energy savings and are on the path toward NZE. It will
also explore an example of a non-hospital building that
has achieved NZE, providing insights into achieving
this goal in practice. Insights from hospitals that are
on the path to NZE and other building types that have
realized this goal help identify barriers unique to NZE
and hospitals and help identify next steps for the health-
care sector to design-toward and achieve NZE.
Average energy use in U.S. hospitals
Hospitals in the United States (U.S.) use nearly 8% of
all national energy (1), emitting an equivalent amount
of greenhouse gasses, and exceed $9 billion in annual
energy costs (2). In 2016 the private and public health-
care markets combined spent $464 billion nationally
on new construction (3). Most of this construction
occurs at code minimum energy standards, missing
large opportunities for energy savings. With such
large infrastructural investments, a focus on energy
and environment could bolster positive environmental
and economic impacts. Concerted efforts are being
made to improve codes, strengthen standards, and
accelerate deeper energy savings across the building
sector. Hospitals can reduce energy use with the aim of
achieving net-zero energy (NZE), though it would be
a heavy lift requiring a shift in typical hospital design.
Understanding how typical hospitals use energy is
pivotal to informing NZE design. On average, U.S.
hospitals consume 231 kBtu/ft²-yr (729 kWh/m²-yr),
ranging from 110 kBtu/ft²-yr (347 kWh/m²-yr) to
450 kBtu/ft²-yr (1420 kWh/m²-yr). For compar-
ison, typical office buildings use 78 kBtu/ft²-yr
(246 kWh/m²-yr) on average (4), and international exam-
ples use about 50% less energy than typical U.S. hospitals.
How U.S. hospitals can realize
net-zero energy
HEATHER BURPEE
University of Washington
Integrated Design Lab
burpeeh@uw.edu
REHVA Journal – October 2017 31
Articles
Data shown in Figure 1 highlights the U.S. national
average for hospital energy use as it compares to
several specific examples of hospitals in Norway and
Denmark (5). These data are corroborated in an older
study compiled by the Center for the Analysis and
Dissemination of Demonstrated Energy Technologies
(CADDET), which shows the U.S. as one of the largest
energy users for healthcare, second only to Canada (6).
Defining Net Zero Energy (NZE)
In 2015, the U.S. Department of Energy published
A Common Definition for Zero Energy Buildings,
providing common definitions for Net Zero Energy
buildings (7). Their definition for a “Zero Energy
Building”, which this paper refers to as a “Net Zero
Energy” building, is “an energy-efficient building
where, on a source energy basis, the actual annual deliv-
ered energy is less than or equal to the on-site renewable
exported energy.” To simplify this concept, many teams
use a site-based only definition that does not consider
the energy source. The New Buildings Institute has
simplified this definition to only include site energy
implications, stating “Zero net energy (ZNE) buildings
are ultra-efficient new construction and deep energy
retrofit projects that consume only as much energy as
they produce from clean, renewable resources (8).” This
paper applies this definition.
Net Zero Energy “ready” refers to a building with
an energy profile that can realistically be accommo-
dated by a clean, renewable energy source, which may
be purchased after construction of the building. For
example, the building may be built and operate reli-
ably with a low energy profile and later, when funds
are available, a photovoltaic array is installed, which
produces as much energy as the building consumes on
a net-annual basis.
Approaches for significantly reducing
energy in hospitals
Programs such as Targeting 100! (9), ASHRAE’s 50%
Advance Energy Design Guide for Large Hospitals
(AEDG) (10) provide a roadmap for significant energy
reductions in hospitals, presenting a path toward 60%
Figure 1. Hospital energy use in the U.S. vs. Norway and Denmark (100 Kbtu/SF-yr = 315 kWh/m²-yr).
115
112
157
117
201
139
Measured, Operational EUI (site)
Includes all end-uses including lighting and plugs
209
226
90
249
0
50 100 150 200 250
EUI (Kbtu/SF Year)
SELECTED ENERGY USE IN HOSPITALS BY COUNTRY
Average U.S. Hospital
Average Office
Pacific Northwest Hospital 4
Pacific Northwest Hospital 3
Pacific Northwest Hospital 2
Pacific Northwest Hospital 1
St. Olav’s
Akershus
Rikshospitalet
Rigshospitalet
LEGEND:
Denmark
Norway
U.S.
REHVA Journal – October 201732
Articles
energy savings at little-to-no additional capital cost.
These roadmaps outline what is achievable utilizing
current codes and standards, and represent a starting
point for NZE or NZE-ready hospital design. Insights
from recently built hospitals also showcase that lower
energy hospitals are possible. For example, the Swedish
Issaquah Hospital in the U.S. Pacific Northwest.
operates below 120 KBtu/SF-yr (380 kWh/m²-yr),
and the Peace Island Medical Center operates under
100 KBtu/SF-yr (315 kWh/m²-yr). International
examples show that there is consistent achievement of
similar or better results (11).
The major points for Targeting 100!, the AEDG, and
recent built examples include:
1. Hospitals are large energy consumers for somewhat
surprising reasons: Minimum requirements for
ventilation mean that a large portion of the energy
consumed in a hospital is being used to transport
and condition ventilation air. Re-heat energy is the
single largest energy consumer, representing 40-50%
of the total energy consumed in a typical facility.
Hospitals’ internal requirements dictate that air be
very cool in some hospital areas; spaces needing the
coolest air (such as surgery suites) determine the
air temperature traveling through an entire zone.
All spaces needing warmer air (e.g. offices, exam
rooms, patient rooms) require air to be re-heated
at the delivery point. Additionally, hospitals are
densely occupied, operate 24 hours per day, seven
days a week, and house a lot of energy consuming
equipment.
2. To reach low energy targets, designs should:
a. Prioritize Load Reduction through Archi-
tectural Systems. Energy reductions start by
aggressively reducing external climate dependent
loads and activity dependent internal loads. A
simultaneous focus on peak loads and whole
building annual energy loads is important for
solving the energy and cost equation. Smaller
peak loads mean smaller plant equipment which
translates to lower capital cost investments;
lower overall load profiles provide flexibility in
ventilation system choice and mean significantly
reduced annual energy use profiles for heating
and cooling, and thereby, annualized energy
savings. Highly coordinated architectural and
building mechanical systems are required to meet
large load reduction goals. For example, exterior
shading on the envelope significantly reduces
solar heat gain enabling a de-coupled approach
to building heating, cooling, and ventilation
systems. De-coupling heating and cooling from
ventilation of rooms enables much lower whole
building load profiles and significantly reduced
peak loads.
b. Re-Heat Energy Reduction through Building
Mechanical Systems. Strategies for reducing or
eliminating re-heat include de-coupling space
tempering and ventilation for most spaces; fluid
rather than air-transport of heat and cooling for
peak conditions; and the final distribution of
heating and cooling to each space via a bundle of
de-coupled systems such as radiant heating and
cooling panels. These systems require a limited
load profile and thus, require prioritizing load
reduction strategies. Optimized heat recovery
from space heat and large internal equipment
sources also reduces the overall energy demand
as does including advanced HVAC and lighting
controls: turn off what is not in use.
c. Efficient Plant-Level Equipment. Provide the
ability to capture heat in the most efficient way.
Utilize advanced heat recovery at the central
plant and implement heat pumping, or enhanced
heat recovery chillers paired with highly efficient
boilers.
Implication for on-site energy
production
Targeting 100!, the AEDG for Large Hospitals, and
recent built examples show that achieving an Energy Use
index (EUI) of 100 KBtu/SF-yr is possible alongside
current codes and standards. Even though these exam-
ples utilize significantly less energy than their typical
counterparts, they still use too much energy to achieve
NZE by simply adding renewables. The total energy use
for a 250,000 SF hospital operating at 100 KBtu/SF-yr
would require a 6850 kW photovoltaic array, meas-
uring nearly 500,000 SF (in Seattle, WA, U.S.), or a
slightly smaller, 4500 kW, 300,000 SF of PV array (in
sunnier Los Angeles, U.S.) to produce enough energy to
offset the total energy demand in an average year (12).
The site area size and cost of PV equipment is not real-
istic to achieve NZE. If these examples reduced their
energy demand to 50 KBtu/SF-yr (158 kWh/m²-yr),
that implies a much smaller array, 3400 kW (Seattle) or
2250 kW (Los Angeles), using just under 250,000 SF
and 160,000 SF respectively (13). An even lower EUI,
more efficient array, or sunnier climate would imply an
even smaller and more affordable array to achieve NZE.
These calculations highlight that in order to approach
NZE, or become NZE ready, a hospital must reduce
its energy footprint significantly beyond what has been
achieved to date in the U.S.
REHVA Journal – October 2017 33
Articles
What is needed to achieve NZE
Roadmaps and built examples show how to significantly
reduce energy in hospitals usually through the natural
gas systems, implying a fuel switch from predominantly
gas-fired plants to all-electric plants. This presents
opportunity to move closer toward NZE and carbon
neutrality through strategies that achieve deeper elec-
tricity savings. Major opportunities that have not been
fully addressed in healthcare are miscellaneous equip-
ment loads (MELs) and plug loads. MELs include fan
power energy both at the plant level and in distributed
systems. Plug loads capture all energy connected equip-
ment including computers, TVs, imaging equipment,
and rolling devices such as IVs, beds, etc. As has been
done with the hospital building as a whole, a coordi-
nated research effort is needed to first understand the
energy profiles of this equipment, then reduce energy
demand where there is the most opportunity. This will
likely start with choosing the most energy efficient
devices, then turning off equipment not in use from
full-power mode through more sophisticated controls.
Re-designing devices to include energy efficiency as an
important criterion will help move this area forward
without negatively impacting the quality of patient
experience or patient care. Efforts such as Energy
Star for commercial and residential equipment show
a similar path for commercial and residential equip-
ment, and can effectively rate equipment and achieve
energy savings. Energy Star has initiated partnerships
that will lead to ratings for some large healthcare
equipment, such as MRI machines. Once Energy Star
equipment is available, a reliable energy attribute can
become a specification criterion for designers involved
in acquiring new healthcare equipment. Beyond MELs
and plugs, careful analysis and research is needed to
determine the necessity of codes and standards that
impact energy-using systems in hospitals. Specifically,
a concerted effort to understand effective and necessary
air-change rates throughout hospitals will help re-define
minimums, potentially significantly decreasing energy
demands, while not compromising (or potentially
improving) quality.
Figure 2. Implication of energy use on net-zero ready potential including relative PV array sizing and relative
coverage of site area (100 Kbtu/SF-yr = 315 kWh/m²-yr).
0 50 100
EUI (Kbtu/SF Year)
IMPLICATION OF ENERGY USE ON NZE POTENTIAL
SITE IMPLICATIONS
400 ft.
100 KBtu/SF Year
= 7,300,000 kWh
250, 000 SF
50 KBtu/SF Year
= 3,650,000 kWh
250, 000 SF
1
2
ARRAY SIZING
TOTAL ENERGY USE
100 KBtu/SF Yr.
1. Seattle, WA, U.S.
2. Los Angeles, CA, U.S.
6850 kW
3400 kW
4500 kW
2250 kW
500,000 SF
250,000 SF
300,000 SF
160,000 SF
2250 kW, 160,000 SF Array
100 KBtu/SF Yr.
50 KBtu/SF Yr.
50 KBtu/SF Yr.
REHVA Journal – October 201734
Articles
Learning from other NZE buildings
Current NZE buildings provide insight into how
hospitals can achieve similar energy targets. The
Bullitt Center in Seattle, WA U.S. is one example of
a 50,000 SF commercial office building that has oper-
ated at NZE since 2013. In fact, this building has
produced more energy than it consumed (making it
Net Positive Energy) in its first three years of operation
(14). Insights from this building include: 1. First reduce
loads through the envelope, 2. Use water-based heat
pumping systems for heating and cooling, 3. Provide
minimum ventilation for fresh air using 100% Out
Side Air (OSA) with high-efficiency heat recovery, 4.
Utilize the outdoor environment as much as possible
for natural ventilation and passive cooling, 5. Install
very low lighting power and using comprehensive
control systems to turn off lights when not needed, 5.
Implement sophisticated building controls that guide
users in energy-using systems, 6. Gain comprehensive
understanding and control of plug loads, 7. Measure
and verify energy use patterns at a granular level to
understand what is working and where improvements
can be made, 8. Since plug-loads and patterns of use
become a bigger part of the energy picture, partner with
building occupants to participate in energy efficiency
strategies and utilization, and 9. Partner with utilities
to ensure a transaction structure that is sustainable and
economically viable for public and private entities as
more buildings approach NZE.
Hospitals are often more complex and sophisticated
than typical commercial buildings. However, there is a
path toward energy and carbon neutrality that is achiev-
able. A comprehensive re-visioning of how a typical
hospital is designed and operated must be part of the
solution for meeting and achieving aggressive energy
targets that are outlined by city, state, and governmental
leaders.
Citations
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expenditure gross energy intensities, 2012” Energy Information Administration (EIA)- About the Commercial Buildings Energy
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(5) Burpee, H., McDade, E. (UW MArch student), “Comparative Analysis of Hospital Energy Use: Pacific Northwest and Scandinavia,”
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(8) “Zero Net Energy.” New Buildings Institute. Accessed September 15, 2017. https://newbuildings.org/hubs/zero-net-energy/.
(9) “Targeting 100!” Targeting 100! September 2012. Accessed September 15, 2017. http://www.idlseattle.com/t100.
(10) Advanced Energy Design Guide for Large Hospitals: Achieving 50% Energy Savings Toward a Net Zero Energy Building. Publication.
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