From LEED to the Living Building Challenge, commercial builders are more focused than ever on creating energy-efficient structures that meet the highest environmental benchmarks while standing the test of time. Yet, approximately 40 percent of total U.S. energy consumption was attributed to buildings in 2016, according to the U.S. Energy Information Administration.

A primary consumer of energy is one of the most neglected by building professionals: elevators. They can devour as much as 10 percent of a building’s energy, which is not surprising considering there are more than 12 million elevators worldwide making seven billion trips and moving one billion people every day. If ignored, elevators can quickly become an environmental and economic drain.

At this point, after decades of technology and machine advancements, new elevators are relatively small energy consumers, to the satisfaction of many building owners and developers. But why settle for any energy being wasted when the opportunity to create a net-zero energy system is possible? The idea of a net-zero elevator system would’ve been unthinkable 30 years ago, but so was the idea of a horizontal-moving elevator—and the first ropeless elevator became a reality this past June.

Creating Net-Zero Elevators

Put simply, a net-zero energy building only produces as much energy as it consumes. One of the gold standards for net-zero energy buildings is the Bullitt Center in Seattle, which dubs itself “The Greenest Commercial Building in the World.” Everything from lighting and daylighting to windows and building envelope technology help contribute to the building only consuming the energy and water it gathers. Everything in the building is optimized for net-zero energy—everything but the elevator.

Creating a net-zero elevator isn’t a new concept; it’s been around for about a decade. But its inclusion has been fairly limited. First, net-zero has only been incorporated on new elevators. Considering new buildings account for less than 2 percent of the annual global total, this is only a fraction of the active elevators worldwide. For example, more than 70 percent of all U.S. buildings are more than 25 years old.

Implementing a net-zero system for new and existing elevators starts with improving the solar footprint. In order to run an elevator previously, solar panels would consume the entire roof space, and those panels often would be located on a completely different building. Once cost was factored in, it would be deemed an unnecessary expense. But today, those solar panels can be installed within the footprint of the elevator shaft itself, making it more practical and cost-feasible.

On the elevator itself, net-zero energy can be achieved through the inclusion of a regenerative drive that recaptures energy when it is in motion. Net-zero energy is also achieved through the inclusion of a smart-learning controller with deep-sleep or hibernation mode and automatic power-down of the cab lighting and fan circuit when the elevator is inactive. LED cab lighting is another important part of a net-zero energy elevator system. Consider this: In a two- or three-story building, a typical elevator consumes more energy from the lighting system than it does actually moving people. Simply replacing halogen and incandescent bulbs with LED lights can deliver the performance of a T5 fluorescent bulb, but with 10 to 15 times the life. This also extends to the backlights for buttons.

Smarter and more efficient technology allows an elevator to regulate its lighting and fan based on usage trends—dimming after some time has passed since somebody last pressed a button, or turning on a two-speed fan to circulate fresh air through the cab when it’s occupied.

Another aspect of a net-zero elevator system is switching from relay to microprocessor controls on the board, which reduces the amount of energy and energy losses by having more integrated circuits per area of the printed circuit board, making the controller and circuitry more energy efficient. In addition, elevator companies have developed special AC motors with variable frequency drives that are designed for lower RPMs required by elevator systems, thus eliminating the need for reduction gearing.

Roughly 300 buildings worldwide, all net-zero structures, are being certified under the Living Building Challenge. To achieve this, builders and contractors were opting to eliminate multiple-story buildings because they require more elevators and more energy, but this approach consumes more real estate and conflicts with the urbanization trend that will see 70 percent of the population living in cities by 2050. Net-zero elevator systems open up the possibility of more vertical sustainable construction.