Hospital buildings account for 40% of the GHG emissions that contribute to climate change and 76% of electricity use in the United States. According to the University of Washington, construction and operation of hospital buildings use 5% of all energy consumed in the United States, including buildings, transportation, and industry." While this may be a startling statistic to some, given the significance of the healthcare system, there are many opportunities in healthcare infrastructure to reduce the energy consumption of hospitals nationwide.

Balancing Act 

Health and safety requirements can make efforts to mitigate climate change a unique challenge for hospitals, as there are almost competing standards to save energy and meet indoor requirements for patients and doctors. Converse to the typical work environment, healthcare facilities are comprised of:

  • Traditional office employees and maintenance teams 

  • Doctors, nurses, and surgeons 

  • Patients seeking medical care, some which have extended stays

On the Rise 

In response to community healthcare demands, between 2015 – 2021, 366 new hospitals were built in the United States. A unique characteristic of hospitals is their energy consumption relative to their actual size. Hospitals only account for about one percent of a built area. Yet, they can be responsible for five percent of its energy consumption. This is primarily due to: 

  • Specialized Medical Equipment and high-power lighting in energy rooms

  • Ventilation Systems and Filtration

  • Continuous operating hours to accommodate employees, patients, and visitors (some operate 24 hours a day, seven days a week, 365 days a year) 

From concept to fulfillment, hospital building construction requires a considerable time investment. It can take roughly five to ten years to complete a project, and larger developments can last more than twenty years. While many firms have set goals to design for net-zero by 2030, the reality is that many are still falling short, as designs should already meet net-zero goals. So, how can we optimize an existing project for net-zero and beyond?

Key Metrics 

Simulations can help design teams during project ideation. You can run various simulations to optimize for energy, carbon, daylight, interior quality, and cost. With that being said, let's cover some key metrics and ways you can simulate for optimization.

1 Energy Use Intensity (EUI) 

EUI measures yearly energy use, usually electricity or natural gas, per area or units of kBtu/ft2/year or kWh/m2/year, per area. It is typically measured using an energy model of an existing building or by calculating annual utility bills.

EUI focuses on benchmarking and comparison. You can track efforts toward a goal of zero energy consumption because it allows you to compare buildings of varied sizes. For purposes of this article, we'll focus on site EUI, and here is why:

  • Easier Calculation: You do not need to know anything about the site or utilities to calculate it. 

  • Commonplace: When not specified, it is site EUI.

  • Zero site EUI equals Zero source EUI: Once you get to nothing, they equal each other. 

 Let's segue way back to the metrics, what they are, and how to simulate them.

2 Spatial Daylight Autonomy

Spatial Daylight Autonomy (SDA) is the percentage of occupied floor area receiving 300 lux for at least 50% of its regularly occupied hours. What does that mean exactly? It is the amount of natural daylight available to people in a building, opposed to electric light. Studies report that natural light improves productivity, mood, and health, critical for hospital wards where people stay for days and weeks. 

Takeaway: Ample daylight results in happier and healthier people. SDA not only provides light needed to conserve energy usage during the day but also improves the atmosphere inside the hospital building.


3 Annual Sunlight Exposure (Glare Factors) 

Annual Sunlight Exposure (ASE) is the percentage of occupied floor area receiving 1000 lux for at least 250 hours per year. Oppositely, if SDA seeks to quantify available natural daylight, ASE accounts for too much sun and brightness. Excessive levels can hurt occupants’ eyes and can create an unpleasant experience for staff and patients. Additionally, glare equates to solar gain. And, when you mitigate solar gain, it reduces cooling energy and associated costs. 

Takeaway: Reducing ASE helps keep occupants happy and comfortable. It also plays a role in cooling energy reduction.

4 Operating Costs 

Operating costs are dollars paid for energy used onsite on an annual basis. You can calculate this with building energy models or measure from annual utility bills. Targeting 100 is a valuable resource for information. Hospitals receive roughly twenty dollars of gross income for every dollar they make, making money saved on energy worth twenty times as much. 

Takeaway: When you cut energy costs, you reduce operating costs. Funds funnel back into the hospital to improve patient care.

5 Total Quality Views

Another important metric related to daylight includes quality views. Quality of Views is the percentage of floor area with multiple sightlines, views of the sky, or unobstructed views. LEED credits help to quantify. Why measure the quality of views? Quality of views can improve patient wellness by improving the living conditions of long-term patients. 

One Caveat: include internal partitions when understanding views. For example, if a wall is in the way, we won't be able to see the outside for deep floor plans. The point is: do you have all the necessary information for the internal layout?

Takeaway: Quality views lead to happier patients, better outcomes, and help people stay connected to the outdoors.

6 Construction Cost

Businesses need to be mindful of budgets. Construction costs are the dollars spent on the construction of a building. To determine the investment, work with an estimator, or use an automated tool. Not every hospital has private contractor institutions or receives independent funding, making budgets and limitations a real concern. 

Takeaway: With spending limits, hospitals want to minimize costs, so each dollar goes toward patient care.


7 Operational Carbon Dioxide Equivalent

Operational carbon is the greenhouse gas emissions from energy consumed on a property site. This is known as CO2E, which stands for “CO2 equivalent”, not emissions (typically, expressed as metric tons or kilograms). Calculate with computer simulation, such as a building energy model. Why calculate it? It contributes to climate change and has a negative impact on human health.

Takeaway: Reducing operational carbon is an opportunity to improve the health of communities within the hospital region.

8 Embodied Carbon 

This statistic continues to gain traction and has become more critical over the last ten years. It is GHG emitted during the construction of a building, kgCO2e or Tonnes of CO2e.

As we reduce carbon emissions from building operations, emissions from building construction become a more prominent contributor. You can simulate this through an LCA or a carbon calculator (EC3) but need EPD's from manufacturers. For example, what is the carbon content of materials of used to construct a building? 

Takeaway: The goal is to minimize the complete carbon life cycle of a building.

In summary, maximize SDA views and minimize all other metrics. The result is a quality hospital. Before we cover a workflow, we need to touch on benchmarks.


It is critical to determine attainable and testable goals to reduce energy use. Benchmarking helps track practices and performance and compares data against industry performance standards. Without benchmarks, you are not able to measure efforts. One way to benchmark is to compare your EUI with hospital buildings across the United States.

Every hospital is unique, with different hours and departments that factor into energy use. The average EUI in the United States is 249. Where is this energy used?

Example End-Use Breakdowns

Mass General Hospital is an older building in a constant state of renovation. The EUI is 407. From the NREL study, we see some expected numbers: equipment and light at 21%, heating and reheating at 26%. Often, medical imaging would be high because of greater kilowatt demand. At .5% that that is not the case.

At Legacy Salmon Creek Hospital there is a lower EUI at 214. The split shows most of the energy use is from reheat, equipment, and lighting. So, we have a target for energy reduction, but we cannot just make a change.


So, we have a lot of data. How do we prioritize? Decisions require coordination with hospital stakeholders. Purchasing a more efficient chiller or boiler can make a significant impact, but that investment does not happen without consensus.

Unlike an office that may have a CEO or building owner, many teams of people in a hospital provide input on design and operations. In terms of regulations, most states have an AHJ or an authority with jurisdiction over hospital requirements. This affects decisions as well.

In terms of workflow, we won't look at isolated elements. Instead, start with: 

  • A few models and massing study

  • Site Rotation

  • Define options for review

  • Run them as bundles all at once

 Don't isolate elements: consider HVAC, envelopers, and operations together. Get metrics such as energy, cost, and daylight out. This allows us to decide on an optimized design and holistic approach.


What are the Benefits of Energy Optimization?

hospital building

1 Cost Savings 

More efficient hospitals have fewer operational costs. Work with key stakeholders to identify areas for improvement and intelligent investments. While energy may be a smaller portion of operating costs, investing yields long-term dividends. If difficult to see the short-term payoff, long-term benefits are less costly for operating budgets and patients.


2 Interior environment 

Energy-efficient hospital buildings improve the well-being of employees and patients. This is important for staff members such as surgeons, nurses, and office personnel, who spend a lot of time in this critical care environment.

With some patients spending weeks to months in a hospital to heal, air quality and access to outdoor views provide comfort. Natural daylight leads to better moods and improved employee productivity.


3 Lessen Climate Change 

Studies show that carbon emissions from hospitals are a major contributor to climate change. Reducing their energy consumption leads to fewer carbon emissions, reduced greenhouse gasses, and air quality improvements. Another benefit is improved air quality for the communities in regions around healthcare facilities.

4 Better Health 

Established to make a positive impact on the wellness of people, hospitals have a personal stake in preventing widespread emissions. When hospitals contribute to air pollution, they don't just contribute to climate change; they can also harm patients.

Emissions contribute to air pollution, which can cause illnesses such as asthma, stroke, and heart disease. Health care organizations approach efforts from a place of "first do no harm" so efforts to reduce energy consumption should connect to their mission; another reason why hospitals should reduce their carbon footprint.


Hospitals present a wealth of opportunities for more efficient operations that reduce carbon emissions. Review key metrics, establish benchmarks, develop workflows, and work with key stakeholders to prioritize targets that minimize energy consumption and make business sense for your hospital.

Patrick Pease, PE is the Mechanical Engineering Director at cove.tool. A member of ASHRAE, IBPSA, he has over nine years’ experience in the AEC industry.


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