Office building sustainable design has changed
COVID, employee well-being and indoor air quality issues have all changed office buildings sustainability goals
- Daniel Donahoe, PE, Senior Mechanical Engineer, LEO A DALY, Omaha, NE
- Tyler Jensen, PE, LEED AP, Studio Leader, ESD, Chicago, IL
- Brad McNiff, PE, LEED AP, WELL AP, Principal, GHT Limited, Arlington, VA
- Gerald Williams, PE, LEED AP, Senior Mechanical Engineer, CRB, St. Louis, MO
What unusual systems or features are owners requesting to make their office facilities more efficient?
Daniel Donahoe: We’re moving toward the electrification of buildings and a focus on being carbon neutral versus net zero. Carbon is the performance target now, which is moving the industry toward electrification. This means finding solutions, especially in colder climates that traditionally rely on natural gas. We’re looking at equipment, heat pump technology for example that can meet heating and cooling needs while reducing carbon emissions.
We are seeing more requests for photovoltaic systems, but those have a high likelihood of being value engineered out because the payback is so poor — at least in the Midwest. On the coasts, we’re seeing the needle move more on PV because paybacks are better due to different utility rate structures. More municipalities are dictating policies against the use of natural gas. We’re also seeing heat pumps that scale up to commercial scale.
Brad McNiff: For build-to-suit projects, we see more flexibility being requested in MEP systems. Also, owners of private office buildings are requesting options to enhance individual occupant control of their environment.
Gerald Williams: The most energy-efficient office is the office that is no longer needed.
The post-pandemic rise of people working from home eliminates the need for dedicated office space for every employee, which can substantially reduce the size, energy use and related operating costs of a traditional brick-and-mortar office. Office spaces may become much smaller as they get used more for hoteling stations, occasional meeting rooms, large document printer rooms and other similar support areas not readily available in-home offices.
What types of sustainable features or concerns might you encounter for office buildings that you wouldn’t on other projects?
Tyler Jensen: Built-to-suit office buildings allow the design team to plan for the full building energy use. Core and shell office buildings, on the other hand, can be difficult because the design team is only accountable for a portion of the building’s energy. Base building systems can be optimized, but tenant plug loads, lighting and operation is largely out of the base building design team’s hands.
What types of renewable or alternative energy systems have you recently specified to provide power?
Daniel Donahoe: The PV industry is experiencing something similar to what LEDs encountered when they were first introduced. There are many small companies making PV products, but the trust just isn’t there from many clients that they will be supported in the long term.
Tyler Jensen: Recent highly sustainable office projects have used solar PV to offset all or a portion of the building energy use. Even efficient high-performance office buildings require about 1 square foot of PV roof area for every 2 square feet of building energy. For multistory and high-rise office buildings, this becomes a challenge for clients who want to achieve net zero energy on-site. To address the challenge, recent projects have used adjacent site areas to mount PV panels or considered power purchase agreements with a third-party provider to install and maintain off-site renewable energy sources. Most net zero certification programs acknowledge the limitations of on-site renewable energy production and allow for off-site production.
What are some of the challenges or issues when designing for water use in such facilities?
Brad McNiff: Water quality is extremely important for any use in a building. Most process water use systems require chemical treatment to prevent equipment and piping from fouling and to reduce potential for health hazards. Understanding acceptable levels of risk and the owner’s capacity to operate and maintain treatment systems is key. For domestic water systems, knowing the incoming water quality is important to identify what levels of filtration are needed. Proper temperature maintenance of hot water systems is critical to development of Legionella.
How has the demand for energy recovery technology influenced the design for these kinds of projects?
Daniel Donahoe: We’ve seen an increase in municipalities who have advanced energy codes. IECC 2015, which requires energy recovery on ventilation air, is driving use of that technology in a lot more projects. There are many ways to do energy recovery — wheels, plate and frame, coils — for commercial buildings. For commercial buildings, we’re seeing a lot of energy wheels, which is the most efficient. Whereas in health care, these aren’t as popular because of cross-contamination concerns between air streams.
Tyler Jensen: Current energy codes require energy recovery from exhaust air streams in most climate zones for all but the smallest systems. We are looking at all available exhaust air streams to identify the best energy recovery means. A recent office tower repositioning project with a new food court even included a kitchen exhaust energy recovery system with specialized, coated coils to transfer heat to the makeup air system. The project is located in Chicago where kitchen makeup air heating is a major energy use so the system provided significant energy savings.
Brad McNiff: Requirements for energy recovery systems are increasingly prevalent in energy codes. For HVAC systems, outdoor air conditioning is a major component of HVAC energy use and one that can be significantly reduced with energy recovery technologies. This is included in most ventilation systems our firm designs.
High-performance design strategies have been shown to have an impact on the performance of the building and its occupants. What value-add items are you adding these kinds of facilities to make the buildings perform at a higher and more efficient level?
Daniel Donahoe: We’ve used electrochromic glass on several recent office building projects, including headquarters buildings for Carson in Omaha, Nebraska, and American Savings Bank in Honolulu. This adds value by allowing users to dial in the exact amount of daylight they need, reduce heat gain and glare on sunny days and dial back the amount of artificial cooling or heating they need to do. We’ve also used geothermal wells and chilled beam cooling systems, including the headquarters of Cobalt Credit Union in Bellevue, Nebraska. These technologies add value by reducing energy consumption significantly.
Brad McNiff: As one example, building main entry lobbies are an important occupant experience that are typically entirely transient spaces. Occupants usually only spend a short time in lobbies and are dressed for the day’s weather. The owner/design team recognized this for the Amazon Metropolitan Park project and rethought the lobby experience by creating a transitional comfort zone. This concept included relaxing the temperature and humidity set points, supplementing with high-volume low speed fans and radiant floor heating as needed. The result is a smoother comfort transition for indoor occupants dressed for outdoor weather and energy is saved by not conditioning the space to a seated office-like environment.
What level of performance are you being asked to achieve, such as WELL Building Standards, LEED certification, net zero energy, Passive House or other guidelines?
Tyler Jensen: A minimal level of LEED certification is now a baseline for many office buildings. Office buildings are also increasingly promoting employee health and wellness as a means to encourage employees to feel comfortable returning to the office. WELL certification is gaining prevalence. We are also seeing an increased interest in net zero certifications such as LEED Zero Energy, Zero Code and others as companies look to achieve their sustainability goals.
Brad McNiff: LEED certifications have historically been the most sought-after credentials in the Washington, D.C., metropolitan area. Indeed, D.C. has the most LEED square footage per capita of any city in the country. Our firm has received a lot of client interest in WELL and Fitwel projects, but some clients ultimately elect to incorporate strategies from those programs and forgo actual certification. The local climate makes net zero energy a challenge for high-rise office projects in the D.C. area, but new net zero carbon certifications are an attractive alternative that’s also getting a lot of interest.