Conventional real estate wisdom gives a commercial building a lifespan of around 30 years. But the sheer scale of high-rise structures and the quantity of materials and energy that go into them means they will be around for much, much longer, with lifespan measured not in decades but in generations.

Super-tall and super-slender buildings need to be extremely strong. Elements such as cladding or mechanical and electrical systems may be upgraded, but their immense structures are effectively permanent features of the urban landscape. In this way, today’s state-of-the-art towers have more in common with medieval cathedrals than with their low-rise contemporaries.

“In the history of the world, only four buildings taller than 150m have ever been demolished,” says Bill Price, director at WSP in London. “For a large building in an urban setting, studies show that it will cost more and take longer to take it down than it did to put it up. That means that when we’re designing and constructing a tall building, we need to remember that it’s essentially going to be there forever.”

Bill Price suggests that designers should think more carefully about how a building might eventually be demolished from the start. But more immediately, they need to make sure towers can adapt to change, and consider a range of interlinked technological, social and environmental factors that will impact on the built environment.

There are good commercial reasons for designing flexible spaces too. Office buildings need to be able to accommodate different occupier groups to make them as leasable as possible. Because corporations are increasingly seeking locations that offer more diverse experience for their workers, they need to attract novelty-seeking millennials and to spur cross-disciplinary thinking and innovation.

The ability to respond to fast-changing workplace trends is also key to maintaining the longer-term value of a building. Technology is already removing the need for large support spaces, points out Andrew Cantor, vice president at New York developer Related. “There will be no need for large file rooms or storage rooms as there has been in the past, and even servers have diminished in size or been moved off site into the cloud. So the amount of space each person needs to work is smaller and there’ll be more people on each floor, putting pressure on elevators and washrooms.”

The challenge is not just to size building systems for potentially greater loads but to keep structural elements as unobtrusive as possible, with no columns on the floor plates and floor-to-ceiling windows so that spaces can be reconfigured anyway a tenant wants. The same goes for residential towers – internal columns interrupt views and limit buyers’ options.

The economic challenges of mega-tall towers mean that they may sometimes undergo drastic changes of use, even when the design is well advanced – keeping building systems engineers on their toes.

Now under construction, 528m China Zun Tower in Beijing was originally planned as a mixed-use development providing 380,000 m² of offices, hotel accommodation and serviced apartments. The biggest challenge for the services engineers was always reconciling the unique form of the building – flared at the base and the top – with the demand for services and vertical transportation created by its mix of uses. Then the decision was taken to convert the whole building to commercial space. “This dramatically increased vertical transportation requirements, but the construction was already fixed, so it wasn’t possible to make any changes to the available space in the core,” says Vincent Tse, managing director of building systems for WSP in China. “Our solution was to add more sky lobbies, so there are now three double-decks spaced throughout the building.”

One of the most significant challenges that all buildings will face in the relatively near future is the impact of climate change – a moving target as the century progresses. How will buildings and their surroundings be affected by much heavier rainfall or more frequent droughts, what toll will more frequent extreme events take on structures and facades, and how to maintain comfortable conditions for building occupants when average temperatures could be much higher than today?

“The challenges that climate change will pose need to be considered in every building, but particularly those that will be around for a long time,” says David Symons, director of Environment & Energy at WSP in the UK. “In 50 years, peak summer temperatures in London are forecast to be 6.5°C higher than they are today. By 2100, they could be around 10.5°C higher. Our research shows that today’s building design codes are wholly inadequate to address these future temperatures. Over 80% of Londoners already claim their flats are too hot in summer, with newer homes having more of a problem.”

Technology to the Rescue

To address hotter temperatures, mechanical and electrical engineers could just design larger cooling systems. “But that will create massive extra energy demand – for cities and for building owners. That’s challenging when energy prices are forecast to be about 30% higher in the UK by 2030. So energy bills will be much higher too.”

The alternative is to use emerging techniques that use fresh air from outside and the thermal mass of buildings to maintain comfortable temperatures. “That becomes even more of an option in a future world which is anticipated to be purely electric. By 2050, some cities will be all electric for heating, for power, for travel. At a stroke, that transforms air quality and reduces noise levels.”

In temperate climates today, windows remain shut against the noise and pollution of city streets, and because buildings are designed to rely on air-conditioning systems. “But why would you do that into the future? You could imagine a world in which there’s no reason not to open the windows.”

Driverless cars promise to change patterns of land use in cities too: “At the moment, quite large amounts of valuable space are given over to car parking,” says Symons. “In the future, at the very least you could have much tighter parking spaces because the cars park themselves. At best, you don’t have car parking at all in the building – if you do drive yourself to your tall building, the car then goes off and parks itself on some cheap land somewhere else and comes to you when you need it.”