Steven Truss* and Michael Seddon**
Vertical transportation is what makes multi-storey buildings possible. So what happens when enclosed spaces, push buttons and efficiency become the problem rather than the solution?
By Steven Truss, director – head of vertical transportation, and Michael Seddon, associate director, WSP
COVID-19 has challenged vertical transportation strategies in tall buildings, probably more than in any other building type.
As real-estate prices surged in downtown areas, elevators have come at a premium both in higher operational costs and reduced rentable areas. As a result, vertical transportation design focused on optimizing services by increasing speed, sizing components efficiently and installing smarter control systems, to reduce the number of elevators required and therefore the size of the building core. Office buildings have a high density of population, ranging from 1 person per 6m2 to 1 person per 12m2. As they reopen in the aftermath of the pandemic, there will be concerns about physical distancing and about touching surfaces. Both of these are particularly relevant in the case of elevators: by definition, people are required to be in close proximity inside elevator cars, and systems are normally operated by pressing buttons. This presents immediate issues for tall buildings, as well as longer-term strategy issues.
Reducing elevator occupancy will significantly impact building operations.
Under social distancing guidelines, the maximum occupancy of a large, 21-person elevator car might be just four people. For a 17-person car, it would be two and for smaller cars that would normally hold 13 people, one. That’s a huge reduction in capacity and will require a rethink of how we use space. What will be the new “acceptable personal space allowance” that vertical transportation design will have to accommodate, and what impact will this have on existing buildings?
As offices start to reopen, occupancy levels may need to be restricted because the elevator system cannot move the required population at peak times of the day, due to the need to observe social distancing.
There will have to be restrictions on the number of people entering a building, with staggered arrival times and enforced stair use on lower levels. Elevators will also have to be cleaned much more frequently, with hand sanitizer provided in the lobbies and inside the cars. People may try to avoid touching the controls with their hands by using other methods, which could cause further delays in the system and a higher rate of breakdowns. In a world where automation and optimization have become key, staff will be required to control the flow of passengers into elevator lobbies.
There are various ways in which we can modify elevators to limit the number of people travelling in them, depending on the age of the system.
The design life of an elevator is typically 15-25 years before it needs to be modernized or replaced, but many buildings have units that are older – there’s a huge back stock ranging back to the 1970s. There’s no way that we could bring the technology and control systems within all of those elevators up to modern standards quickly. It might be possible to limit the number of occupants by setting a lower weight limit for each car. Most elevators have a load weighing device, used to prevent it carrying a higher load than it was designed for. This is typically set at 80%, but could be reduced to 20% to restrict the number of people to a safe level.
More complex vertical transportation systems that use destination control or energy-saving technology based on complex algorithms might be more difficult to adjust.
In recent years, vertical transportation strategies have been designed to minimize energy use. For example, newer elevators are fitted with much more sophisticated electronic load weighing devices, which measure the strain on certain components in order to apply the minimum amount of torque to the motor to move the weight in the car. The other area of efficiency is in the management of passengers. With hall call allocation control, for example, you present your swipe card at the lobby entry speed gate or elevator control system. It knows where you need to go to, summons an elevator and tells you which one to board. The advantage is that this is completely touch-free, but the problem is that the efficiency works directly against social distancing. Hall call allocation clusters people who are going to the same floor or sequential floors, so that the car only makes a limited number of stops with a greater number of people inside. That has two effects: it makes the cars busier and it means that people cluster around a specific entrance in the lobby, both of which work counter to social distancing. WSP’s VT team is working with elevator suppliers’ R&D teams to explore options for reducing the sensitivity and efficiency of these control systems, to allow the elevators to be dispatched containing fewer passengers.
Can elevator manufacturers detune or desensitize the control systems or reset the load weighing devices?
At the moment, we don’t know how easy it is to do that. Offices that use these complex controls may need to introduce a temporary concierge stationed before the speed gate or turnstiles to restrict the flow of people into the elevator lobby, to help manage crowding during times of high demand. Each tenant in the building can control the lobby on their level, but it will still be crucial to address the underlying algorithm technology, to make sure that the elevator isn’t stopping and allowing more people into the car.
Post-pandemic, people may remain reluctant to interact with elevators.
With advances in smart building and smartphone technology, there are already solutions that reduce the need to touch the controls. For example, sensors in residential buildings can enable the system to understand when a resident appears to be approaching and send an elevator to that level.
Technology coming on to the market could almost remove the need to touch anything at all.
In smart buildings, building users might wear keyrings or fobs integrated to the security system that would enable their movements to be tracked. Sensors in lobbies would detect that you’ve turned left towards the elevators and start preparing a car for you. Many security systems now support virtual fobs, by interacting with your phone or smart device. They could potentially go one step further, allowing employers to schedule arrival time elevator access to spread out peak demand. This strategy may ultimately be the best for larger commercial tenants occupying multiple floors, who have greater control over the occupancy of elevator cabs. The bigger question is whether people really want their phone to be controlling their lives to that degree. Do you want to be mapped by your mobile phone signal and for your phone to exchange that information with the building? That’s a whole different debate.
Stairs may become a more prominent consideration in buildings.
They are more open by definition, and there is better visibility, which makes social distancing easier. Stairs also support wellbeing strategies by encouraging people to move more. But there are only so many flights we can expect people to walk up. Industry standards recognize that if people work on the first floor of a building, 90% of them will walk up. On the second floor, that drops to 50%, and the third 25%. Above that, it’s elevator-only traffic. For tenants taking multiple levels in commercial buildings, convenient access stairs should be encouraged within their individual domain. As with elevator buttons, handrails are likely to become high-traffic touch points so they will require enhanced cleaning, as well as hand sanitizer dispensers at entry and exit points.
In the longer term, it’s unlikely we will be designing buildings to allow 20m2 per person to accommodate social distancing.
For a building to make commercial sense, the rental stream has to support the business case, so it has to have a reasonable population. To make a large building practical, the total area of elevator cores has to be as small as possible and it’s always a fine balance between space-take and elevator performance. In very large buildings, we already use double-deck elevators to increase capacity without taking up extra space, as well as algorithm-based controls to manage it efficiently. The shape and size of buildings may change, but the population will still have to be fairly high in order for them to make financial sense. The crucial consideration will be the amount of space that has to be allocated to a person within the building and how much space will be acceptable for a person travelling in an elevator car. This might mean that future buildings are designed to accommodate fewer people in the same size footprint, with larger elevator cars to provide increased personal space.
* Steven Truss, Director – Head of Vertical Transportation, and **Michael Seddon, Associate director, wsp.com