How to Fix the Lift

By Quora on at

High rise buildings have used the same lift system for decades. So why mess with a good thing? Because that good thing is one major waste of space. Friends, it's time to redesign the lift.

The Problem

With only a few exceptions*, high rise buildings use lift designs that haven't radically changed in decades. We place a single cab into a long vertical shaft that runs either the full height of a building or, in the case of some very tall buildings, for a small portion of the building's full height. This means that at any given time, only one floor of a lift shaft is in use, while all of the remaining floors are empty (and must remain empty) until the lift cab returns to or passes by the floor again. Put succinctly, this is fundamentally wasteful.

To give the discussion some actual numbers, lets take a real building. The John Hancock Center makes an excellent example, as it is conveniently, exactly 100 floors tall and has a whopping 50 lifts. Lift shaft dimensions can vary considerably, but a reasonable size is 8x8 feet. Now, not all lift service all floors, so let's assume, just for argument's sake, that 17 liftd serve the first 33 floors, 17 service the next floors (34-66), and the remaining 16 service the last floors (67-100).

Remember, even if a lift only opens for some floors at the top of the building, all of the floors below are still filled with a shaft and the space is unusable, even if there is no door. So, we have a total of 17x33 + 17x66 + 100x16 = 3,283 lift spaces, and from above, we've estimated that each lift space takes roughly 64ft^2  of space, which means our lifts occupy 3,283x64 or just over 200,000 square-feet of floor space.

In the case of John Hancock, the entire building has 2.8 million square-feet of usable floor area. So our lifts are approximately 7.5 percent of our usable space. That is a lot of unused space!

* Some buildings, Like Tapei 101, use double deck cabs, which help increase the capacity of a given lift shaft. Still these are more a minor evolution than a revolutionary change.

So this is what we have now: every lift running in its own shaft, doing its own thing.

How to Fix the Elevator

One Way to Fix It

I propose breaking the lift shaft paradigm by designing cable-less lifts cars that move in an lift plane, instead of a lift line (shaft). If a lift cab were capable of moving laterally as well as vertically, we could run multiple cars within a single vertical column. To do this we'd need to get rid of lift cables and instead have each lift cab driven by an integral motor system. If we could run multiple lift cabs within a single vertical column, we could radically reduce the number of required shafts, freeing up substantial floor space for other uses, including tenant occupancy.

Basically I propose something that works more like this:

How to Fix the Elevator

So we've gone from six lift shafts to three. Of course, we can't switch to only two shafts, as we need some ability to handle peak loads—such as lunchtime or at the end of the day, when entire floors of people all want to leave at roughly the same time. But with multiple cabs, we can combat capacity issues with high frequency, resulting in comparable or better total passenger throughput.

Fine-tuning would be required to determine the exact reduction in lift shafts that could be achieved, but a solid 50 per cent reduction is certainly a reasonable possibility. In the case of our example, this could mean freeing up 100,000 square-feet of additional tenant space, or 1,000 square-feet per floor.

Of course, this would all be wildly expensive and take some serious technical hurdles to overcome — namely the increased energy needs that come from doing away with the traditional lift counterweights. But hey, you have to start somewhere.


If you had a dream team of engineers and were given an unlimited budget and were told to build something awesome (it could be anything at all), what would you propose the team build? originally appeared on Quora. You can follow Quora on TwitterFacebook, and Google+.

Image: Shutterstock/Gl0ck