Engineering

Energy use in Health Care Facilities

Higher performance and lower costs

BY MARK BRADBY, PE, AND NED RECTOR, PE, LEED BD+C, CEM

While there are many ways to measure the energy usage in a building, one has come to the forefront–Energy Use Intensity (EUI). EUI provides a consistent way to quantify the energy used in a building. EUI takes the overall combined energy consumed in a building over one year in kBtu (thousand British thermal units) and divides it by the building square footage. A building’s energy use includes its heating, cooling, ventilation, plug-loads, lighting and water consumption. By calculating EUI, buildings can be compared and benchmarked against each other. It is important to note that EUI does not factor in climate zones–buildings in more temperate climates will use less energy than buildings in climates with hot or cold extremes. Another important distinction to note with EUI is Source EUI versus Site EUI. Site EUI measures the energy used at the building level, while Source EUI includes energy used at the building plus inefficiencies in energy generation and transmission. Source EUI is usually significantly higher than Site EUI due to inefficiencies in power plants and transmission lines. Source EUI can be reduced by generating energy on-site with renewable energy sources such as solar panels.

Each $1 saved in hospital energy costs is the equivalent of $20 of earned revenue.

Another critical measure of a building’s energy efficiency is the building’s Energy Star score. Energy Star is a government program that takes multiple factors about a building, including how it compares to similar buildings, adjusts for weather and building usage, and gives the building a score from zero (worst) to 100 (best). A building with a score of 75 is considered an average building that meets current energy codes, while buildings with scores in the 90s are considered highly efficient.



When looking at energy use in hospitals across the U.S., Energy Star has published that the median Site EUI for health care facilities is 234kBtu/sf/yr. Facility EUIs range from below 100 to over 1,500kBtu/sf/yr. The engineers at CMTA aim to reduce that number to under 150 kBtu/sf/yr in climate zones 6 and 7. Minnesota is a predominantly heating-dominated region, which increases buildings’ EUIs due to high heating, cooling, humidification and dehumidification needs depending on the season. Understanding where this energy use is going is especially important when trying to lower energy usage. A national publication recently asked hospital staff where they thought most of the energy was consumed–a majority answered they thought the building’s imaging equipment, such as MRI machines and CT scanners, would use the most energy. The true answer is the HVAC system–consuming 56% of the energy in a hospital, with lighting and hot water being the next two highest at 19% and 16%, respectively. The systems designed by MEP engineers consume most of the energy used in a health care facility, presenting a significant opportunity for improvement.

Conventional strategies

In order to improve energy efficiency in the design and construction of health care facilities, it is essential to start at the beginning of the process. Health care providers are comfortable giving the design team requirements for how many procedure rooms or ICU beds are required, but many facility owners do not feel empowered to tell the design team how the building should perform. With a few notable exceptions, energy efficiency is left up to energy efficiency codes and to the discretion of the engineer. One large health care provider is setting a good example by placing an EUI target at the beginning of a project and writing it into the design team’s contract. It is appropriate that a health care ownership team’s highest priority should be patient care. However, lower energy consumption saves costs, and these cost savings can be rolled directly back into providing high-quality care. One recent survey found that for nonprofit health systems, each $1 saved in hospital energy costs is the equivalent of $20 of earned revenue.

When the owner has set the tone with an EUI goal, the design team can work on the massing and orientation of the building to optimize it. For example, a building with a lot of glass on its south-facing walls will require more energy to cool than a similar building with more windows on its north-facing walls. Shading elements on the exterior of the building can also reduce glare and cooling energy requirements. The architectural teams can also play a significant role in carefully detailing the envelope–exterior construction–of the building, which will reduce air infiltration. The design and construction teams will take additional steps to ensure a tight envelope when they know there will be a blower door test to confirm air leakage is within specified limits. This step not only saves energy, but also ensures all air entering the building is properly filtered and conditioned. Other building level opportunities for energy reduction include reducing square footage and floor to floor heights. If there is building area or height that can be eliminated, the heating, cooling and ventilating (HVAC) systems can become smaller.

 It is important to conduct energy and cost modeling early in the design process

When the building envelope and orientation are optimized with the architectural team, engineers can design HVAC, water heating, lighting and building automation systems. An energy model can be created very early in the design process using high-level building-wide modeling. As the design progresses from programming to schematic design, the energy model can be refined as more details about spaces and occupancy are chosen. It is important to conduct energy and cost modeling early in the design process since that is the time when changes can be made to the building with the lowest cost. As more design time is invested in a building, the cost of making changes increases because changes require costly redesign efforts. This approach also avoids unpleasant surprises at the end of the design process–no owner wants to find out their building is going to consume more energy or cost more than budgeted at the end of the design when they are going out for bid.

Lighting can represent 20% of a typical building’s energy consumption, and the adoption of LED lighting has saved a significant amount of energy. Further reductions can be achieved by lighting modeling, shading analysis and right sizing lighting fixtures to spaces. While it may be easier for the lighting designer to have three of four types of lights for a project, an efficient lighting design might have 12-15 types of fixtures. Daylight harvesting uses automatic dimmers that reduce the amount of electric lighting when sufficient light enters through windows or skylights.

Using variable systems can reduce the amount of heating, cooling and ventilation air delivered to spaces during unoccupied times, leading to energy savings when a room or area is not used. Because hospitals have high ventilation and exhaust requirements, energy recovery is often used to reclaim energy from exhaust air–heat energy in the winter and cooling in the summer. Air side heat recovery uses heat wheels or cross flow heat exchangers to transfer the energy. Water side heat recovery uses coils in the exhaust and ventilation air streams to transfer heat. The concept of economizing refers to the practice of making use of the ambient temperature outside the building when conditions are correct to reduce the amount of energy used by building systems. Air side economizers take outdoor air when it is the correct temperature and humidity, filter it and introduce it to occupied spaces. Waterside economizers have water coils that are heated or cooled by the air outside; the water in the coils is then circulated through coils in the building to achieve the required temperature air inside the building. One example of waterside economizer use is during the winter; the outside air cools the coil, which can then be used for cooling loads such as for an imaging machine or data closet that have year-round cooling requirements. 

Unconventional strategies

As energy costs rise, more attention is being paid to new strategies for saving energy. Some of the strategies have been successfully implemented in other building types but have not been widely used in health care. These systems have the benefit of having a positive track record and of being somewhat familiar to contractors and building engineers. Heat pump chillers can be used for simultaneous heating and cooling loads. Even in the middle of winter or the heat of summer, most hospitals have both heating and cooling needs. Domestic water needs to be heated year-round, while cooling is required by imaging machines and computer rooms. A heat pump chiller allows the owner to share heat between these functions.

Direct outside air (DOAS) units can reduce the size of duct mains in a building and provide more control of ventilation airflow and moisture control by providing 100% outside air through smaller ducts to ventilated spaces. This can save energy by improving fan efficiency and improving system redundancy.

At a programming level, patient rooms can be designed so that the same room can be used for different health care functions–a flexible room could be converted from a med-surg room to an ICU or isolation room simply by changing the control of airflow to the room. Flexible rooms could reduce the total number of rooms and therefore square footage required by the facility. The most efficient space is space that does not have to be built.

Many of the high-performance hospitals designed at CMTA utilize geothermal heat pump systems. While geothermal systems have not been widely used in health care settings in the past, improvements in equipment and controls mean they are worth considering, whether for new construction or retrofitting buildings. Many think of geothermal heat pumps as being only used at the terminal level, where many small heat pumps are used to heat and cool zones with loads under 800 square feet. However, large air handler heat pumps are now available on the market and can be used to replace a standard air handling unit. The benefit of this approach is that the replacement work is limited to the mechanical room and does not require invasive replacement of duct mains and branch ductwork.

The journey to high performance buildings is not a simple one. It requires input and careful thought from many diverse groups of people, from physicians to hospital administrators, to architects, engineers and the construction trades. Two important takeaways to consider are: first, start measuring the energy use intensity of facilities. When things are measured, they can be improved. Physicians and building owners can affect the design of their facility by setting EUI goals and comparing their facility to similar facilities in the same climate zone. The second takeaway is: start now. There is no time like the present for improving energy efficiency in health care facilities. There are multiple benefits: to the energy costs of running the building, to improving patient care, to the stewardship of the environment and to the world we leave to future generations.

Mark Bradby, PE, has over 20 years of mechanical systems experience and has been involved in the design of various building types with a focus on health care. Throughout his career, Mark has been passionate about sustainable design, and continues to advocate for the use of sustainable technology and techniques in buildings.

Ned Rector, PE, LEED BD+C, CEM, has over 35 years of various roles in the health care built environment including mechanical contractor and design engineer. As a Certified Energy Manager, Ned holds unique insights into affordable energy conservation and works with owners to understand their potential for energy and cost savings across their facilities.