Shaping future skylines
Chris Edgington, Building Engineer, Arup
When designing and constructing tall buildings, it is critical to build for the future. The longevity of tall buildings is especially important, as they rise above other buildings in a city and come to define the skyline.
Some buildings, such as 30 St. Mary’s Axe (aka the Gherkin) in London, have become synonymous with the silhouette of their city.
When the Gherkin was completed in 2003, it stood nearly alone as a tall building in the Square Mile of the City of London.
While the landscape around it has changed significantly, the Gherkin is still a shining example of what tall buildings can be – the views from its floorplates have transformed, but it is still a beautiful and iconic building more than 20 years later, despite now sharing its spotlight with several other tall, striking buildings.
This recent history is instructive in that it demonstrates how quickly change can occur. The challenge of developing within planetary boundaries and with increasing awareness of embodied carbon as a finite resource illustrates starkly the need to consider the long term when developing.
This is of course the case for buildings of any size – but the greater quantity of material locked into, and the challenge associated with deconstructing, tall buildings suggests that their longevity and ability to adapt must be at the top of the agenda.
The challenge of developing within planetary boundaries and with increasing awareness of embodied carbon as a finite resource illustrates starkly the need to consider the long term when developing. Tall buildings must therefore be made to last, maintaining their relevance and being able to adapt to evolving needs.
This means not only being aesthetically pleasing and made of resilient materials, but also increasingly means being sustainable and mindful of energy and carbon use.
How can the developers of tall buildings rise to these challenges, and shape our future skylines with buildings that will stand the test of time?
Planning London
London is renowned for its tall buildings. It has a track record of setting the agenda for planning and the built environment, ahead of other parts of the UK and beyond. The original London Plan and its subsequent iterations have set the scene for meaningful changes in the approach that developments take, helping to spark wider awareness of and addressing issues – whether in energy and use of renewables, equality of escape, or embodied carbon.
Recent planning guidance requiring early-stage assessment of a proposed development’s carbon emissions and, crucially, a justified comparison of options, is helping to challenge the narrative that development necessarily means demolition – opening new possibilities in how buildings and our public realm will evolve from here.
The planning landscape in the City of London further seeks to discourage buildings that take advantage of their location without giving anything back – helping to create better harmony between the needs of society and the economic arguments in favour of development.
The City of London featuring the Gherkin, Tower 42, Willis Building, Stock Exchange Tower, Lloyd’s of London and Canary Wharf at the background.
Building tall
Beyond the sense of calm that comes from experiencing the views from a tall building, they are of course also an efficient use of three-dimensional space.
Recent developments in assessing and publishing embodied carbon metrics for buildings have the potential to be transformative in helping developers and clients critically assess the whole life impact of design decisions.What of their disadvantages? Taller buildings have to work harder than those around them. With increasing height comes more physics to fight, more people to keep comfortable and uses to accommodate.
They are more difficult to construct, with cranes being increasingly susceptible to windy conditions with height – and hence construction programmes being more risky. In operation, taller buildings need to move more goods, more people, and more air, in order to meet the needs of their population.
But, in doing so, the economics of building, efficient design and operation can be made to align. With increasing height comes a lower tolerance for wasteful or over-design. Even small improvements to geometry or zones can accumulate to meaningful changes to cost, time to construct, or area delivered, all of which can help to align the interests of developers with the interests of the planet.
Carbon accounting
With the challenges of physics outlined above, it stands to reason that all tall buildings have, by their nature, an outsized embodied carbon impact. And they certainly can, but happily they do not have to. Recent developments in assessing and publishing embodied carbon metrics for buildings have the potential to be transformative in helping developers and clients critically assess the whole life impact of design decisions.
For instance, a recently completed tall building was assessed to have an embodied carbon of around 800kgCO2 per square metre A1-A 5 – a number not significantly greater than that of a low to medium rise building. If this can be achieved without the benefit of carbon accounting at early design stages, it suggests that future buildings will be able to do even better. Using carbon as an accounting tool means not short-changing the planet in the interest of a greater shortterm gain.
Considering communities
Another key consideration for tall buildings is social value. Given their scale and the space they take up, many cities are finding creative ways to ensure these towering structures give back to the communities in their shadows.
For example, it has become common to democratise access to tall buildings through different means – whether via destination eateries, viewing platforms or other cultural offers. These are often on the upper floors of tall buildings, in space that would have previously been reserved for the highest paying tenants. To be a meaningful and proportionate use of space and carbon in the medium term, these facilities will need to offer unique experiences to the public. There is an interesting role for planners to align proposals across a wide range of buildings into a coherent proposition for cities such as London.
Fresh thinking can offer opportunities for efficient use of space. For example, The City of London encourages the use of so-called consolidated deliveries – which reduce the number of delivery trips to buildings, and can restrict access to nighttime. That, in turn, opens the door to other uses in formerly industrial-looking loading bays – giving the space a dual use as a through-route or a marketplace, for example.
Prioritising safety
The safety credentials of tall buildings are also paramount. For example, following the Grenfell disaster in London in 2017, safety regulations are now front and centre for newly built – and existing – tall buildings in the city. The ‘equality of escape’ – incorporated into the New London Plan – is one way in which this is being implemented.
Those who work in tall buildings have a responsibility to future cities. They must prioritise safety, social value and sustainability, as well as architectural elegance.
This states that all people, including those with limited mobility, must be able to get out of a building quickly and safely. Buildings over 18m in height must be provided with firefighting cores and associated lifts for the brigade to use. The London Plan builds on this provision, requiring every core to have a lift designated for evacuation.
This lift will have a backup power supply and additional communication equipment to enable it to be used safely during a fire event. This is one example of the evolving regulatory framework that seeks to improve buildings for people, rightly altering the balance between safety and the amount of free space available for other uses.
Delivering for occupants
One of the great balancing acts in delivering commercial office space is in anticipating and successfully meeting future occupier demands. Getting this right means investing energy in planning and predicting trends, and seeking to deliver buildings and spaces that are appropriately balanced – neither over, nor underspecified. Only in hindsight are we really able to assess whether a project met that ‘Goldilocks specification’.
It is striking and hugely welcome, that occupiers now place significant weight on the sustainability credentials of their buildings. Major tenants look not only for high performance against well-known assessment frameworks – BREEAM, WELL, Wiredscore, for example – but also want to understand the carbon impact of buildings.
Building carbon impacts can be assessed in two categories – embodied and operational carbon. It is only recently that embodied carbon assessments have become part of the development lexicon, effectively creating a new specialist discipline. Design teams now use embodied carbon as an accounting metric and decision-making tool – automatically helping to drive down waste in construction before proposals even make it to the planning stage.
Built environment professionals are accustomed to assessing operational energy and carbon, and with assessment and rating schemes like NABERS, we are finally seeing a light shone on the so-called performance gap where buildings have not always performed as their specifiers might have imagined. As designers, we frequently now need to assess both the operational and embodied carbon impacts of proposals, seeking to find objectively the best outcome overall. Sometimes the results are counterintuitive.
An eye on the future
Those who work in tall buildings have a responsibility to future cities. They must prioritise safety, social value and sustainability, as well as architectural elegance. Finding new ways to rise to these challenges, building tall while being sustainable and socially responsible, will come to define the buildings of the next several decades. We now have the technology and ability that our forebearers could only dream of – and our industry has the potential to do incredible things. I, personally, am very excited to see how the skylines of cities will change and adapt to serve the needs of future generations.
Chris Edgington, Building Engineer, Arup