For the sake of illustration, I’m going to do some math. I’d like to calculate, on average, what 25 percent occupancy looks like in a tall building. Using the Council on Tall Buildings and Urban Habitat’s Skyscraper Center, I was able to determine that, on average, tall office buildings in the U.S. have about 45 floors. Let’s estimate that the average floor is 20,000 square feet, which puts us at about 900,000 square feet total for an average tall office building. Assuming that 200 square feet per person is the desired “maximum” occupancy for most offices, that building can hold about 4,500 people comfortably. Under normal circumstances, loading this many people wouldn’t necessarily be a challenge, depending on how many elevators the building has and what kinds of technology it uses.
But now, in order to maintain social distancing protocols, the realities of loading a building to even a quarter of its normal capacity present considerable challenges. At 25 percent occupancy, that means that 1,125 people need to enter the building and get to their floors in a relatively short period of time as most people arrive at the office somewhere between 7am and 9am. Assuming the building has six elevators, each one would need to transport 188 people to their floors in those two hours—a totally feasible objective, if each elevator were operating at normal occupancy. But that’s not the case.
Mark Freeman is the VP of Modernization at Schindler Elevator Corporation (U.S), a branch of the global elevator and escalator entity Schindler Group, a company that has been creating mechanical lifting devices since it was founded way back in 1874. I spoke with Freeman about some of Schindler’s technological solutions that can assist buildings with their reopening strategies. “Normally, we load about ten to twelve people inside an elevator. If we assign just four people or three people, it will provide a more comfortable environment for the user, but it will also lessen the traffic flow,” Freeman told me. My math illustration may seem trivial, but it’s exactly how these buildings are outlining their return to work strategies. “We figure out, with the population of the building and with the current capacity of the elevator, how many people need to be scheduled,” said Freeman.
In our illustration at 25 percent occupancy, we estimated 188 people need to be transported per elevator. If we were loading ten people per car, that puts each elevator at 19 trips, give or take, over a two hour time frame, meaning each trip would have about six minutes to drop its passengers and return to the lobby. Now, if there are four people per elevator instead of ten, that means each elevator will need to take 47 trips to transport the same amount of people, and each trip will need to be about two and a half minutes to stay in the same two hour time frame. Granted, four people should, in theory, require less stops than ten people, but let’s say each of those people needs to go to separate floors that range across the gamut of one through 45. It could take a while.
The need for accurate time estimates is why strategic planning is so important, regardless of the building’s current elevator technology. “We are working with tenants, based on each building’s maximum occupancy, to figure out the best way to schedule shifts. You assign shifts according to people’s floors, and space them out so they are staggered,” explained Freeman. By assigning times based on floors, each elevator will make less trips and take less time, but again, is it enough?
If we return to our illustration, let’s now assume that those 1,125 occupants are divided evenly among 45 floors. Then 25 people need to be transported to each floor. Using six elevators, with four people per car, that’s about seven trips total, meaning each car only needs to make one trip (with the exception of one car making two trips). Since all passengers are going to the same floor, this greatly reduces trip time, too. It’s reasonable that the entire floor could be loaded in as quickly as five minutes, but with 45 floors, loading the entire building to 25 percent occupancy will still take about three hours and 45 minutes (and that’s if everyone shows up on time, all cars are operational, and there aren’t any hiccups). When you take into consideration that most buildings will have different parameters, including the number floors and/or elevators, it could take significantly longer, maybe even half a day, just to reach one quarter of their normal occupancy.
So how can elevator technology help cut down on time spent loading the building? For starters, destination dispatch systems are designed to optimize elevator efficiency and reduce trips. The system determines which passengers need to go to which floors and assigns cars based on that need. In comparison to conventional elevators, destination dispatch increases efficiency and speed by over thirty percent, taking our estimated loading time from three hours and 45 minutes down to two hours and 37 minutes. Not too shabby.
Schindler’s destination dispatch system is called PORT (personal occupant requirement technology). PORT works by allowing “everyone who is scheduled at that time to come in and enter their calls [or floors],” explained Freeman. They do this by using the PORT device located in the hallway of the elevator bank. Using advanced algorithms, “the system sends a car based on floor groupings. It can make decisions based on where they’re going,” Freeman said.
Combining strategic scheduling with destination dispatch technology will reduce trip times, eliminate excess trips, and save energy usage, but does it save enough time and energy to make it worth the installation? “Typically when you do a mod and take a car out of service, tenants have to wait longer. Even with one elevator out of service, it’s still faster because of PORT. And you add the touchless,” said Freeman. Schindler’s PORT Technology comes standard with a built-in (radio frequency identification (RFID) reader that addresses another critical safety component that many buildings need to reopen—touchless functionality.
The RFID reader provides building access control through personalization, and it eliminates the need to push any buttons. “Inside the system you can write a profile for an individual. This means your floor is programmed into the PORT device. So you simply put your credential in front of the card reader, and it automatically knows what floor you need to go to,” Freeman explained. When combined with destination dispatch technology, the call is made the moment the card, or credential, has been read. These readers can also be integrated to work in conjunction with turnstiles and can be programmed to allow individuals to access multiple floors if needed.