Doug Baldock, Lewis James Hunter
September 6, 2023
High-rise ambitions: A systems thinking approach to decarbonising building services
High-rise buildings are helping our cities meet the demands of urbanisation, reducing urban sprawl by going up rather than out.
High-rise buildings are helping our cities meet the demands of urbanisation, reducing urban sprawl by going up rather than out. But in our efforts to decarbonise the built environment, we must consider ways to optimise the design and performance of these tall structures whilst providing the desired comfort level to end users. Achieving this requires a systems thinking approach with engineers, architects and consultants coming together earlier in the design process to optimise building design for increased energy performance.
Systems thinking enhances the coordination between the early decision design features, structural requirements and mechanical, electrical and plumbing (MEP) services. Changing the linear design method to a collaborative approach early in the design process integrates this decision making as part of a connected system, which optimises building designs for reduced embodied carbon.
Commitments from developers and government requirements are fuelling this approach. Recent developments in energy modelling and measurement are also providing practical tools for designers as well as improving the operational energy requirements of high-rise buildings.
The embodied balance between energy and comfort
High-rise buildings contain significantly more embodied carbon in building services systems because they have much more complex heating and cooling systems, as well as other physical infrastructure such as lifts that also emit high amounts of energy once constructed. Taller buildings are also more exposed to strong winds and more hours of direct sun, which increases the energy needed for heating and cooling.
The goal is therefore to find the perfect balance between reducing operational energy, which goes hand in hand with the embodied carbon of building services, and the comfort of the users. If you can reduce the demand for the building through smart and informed design choices at an early stage, then the vast improvements in building systems efficiency can take over and reduce the operational load even further.
Passive measures to influence energy use
A key approach to achieving the energy/comfort balance through passive design is energy parametric optimisation. This considers factors such as:
- glazing ratios
- shading depths
- building fabric options, and
- measures that can be used in a building’s design.
Running multiple options will find the right fit for the individual projects to locate the sweet spot to lower the carbon but still provide an aesthetically beautiful building.
During these early stages, it is essential for engineers to work with the architects and whole design team to consider various floor plans and different orientations to try and find the range of options that not only suit the vision of the building but will reduce the building’s carbon.
This takes into consideration a range of operational factors, including:
- lighting
- ventilation
- heating, and
- cooling.
If the energy used for these activities can be reduced through passive measures, then that ultimately reduces the need for more stringent or complex energy reduction measures further along the design process. For example, if the daylight entering the building through windows is increased, then the internal lighting demand and energy needed to power this is reduced.
There is also a significant amount of design repetition in high-rise buildings due to the compact floor plates, which reduce their internal to external area. This means that designs can be optimised, and installation becomes much more efficient.
But it is not enough to simply reduce demand; you need to also make the remaining ongoing energy use as efficient as possible, which is not easy to do when working against gravity.
The heat is on to decarbonise high-rise
Systems thinking follows an approach to high-rise building services that requires less use, increased recovery and then reuse of energy and materials. This can be explained by considering a high-rise heating system where the aim is to, firstly not require as much heating, and then for that smaller requirement, to recover as much heat as possible to avoid having to generate new heat.
Some of the tools, methodologies and design alternatives to further tackle operational carbon include:
- using heat pumps where the heat that is being rejected from the cooling system is injected into the heating system
- using the condenser loop from the chillers in the basement to preheat hot water cylinders before they are then topped up by water source heat pumps, and
- reducing the amount of duct turns, bends and overall length in the ventilation system to reduce the specific fan power of the air handling units.
One of the main advantages of systems thinking is that rather than designing every aspect of the building for the peak occurrences of either very cold or very hot, you can optimise the design to run the services at peak efficiency rather than part load.
Case study: 2 Finsbury Avenue
Located within the largest pedestrianised neighbourhood in central London, Ramboll is leading the design of 2 Finsbury Avenue, which is a 38 storey, 106,000 sq m (GIA) development, targeting net zero carbon. To achieve this ambitious goal, a systems thinking approach was taken to the design of the British Land development.
The Building Services engineers focused on energy efficiency from the outset, using the latest modelling and measurement methodologies to identify opportunities for improvement. By integrating energy-efficient technologies and design principles into the building's infrastructure, the team was able to achieve world-class levels of energy performance.
The team undertook extensive rationalisation to minimise construction interventions, employed circular economic thinking, resource efficiency, operational efficiency and a hybrid energy concept.
Hybrid energy is a fresh approach to systems design that delivers leaner and lower carbon buildings. Standard design regularly results in building systems with up to 50% more electrical capacity and 30% more heating and cooling capacity than needed. Using data and analysis to design building systems more efficiently, ultimately delivers considerable savings in capital expenditure and CO₂.
The push and pull through the system
The idea that you can take every piece of a building and consider how it will work within its whole is essential to the systems approach. Everything you select and every decision you make has an impact on other services.
Energy efficient high-rise buildings don’t have to be uninteresting or uninspiring structures. If anything, an increased focus on decarbonisation can lead to more creative designs. Systems thinking allows engineers and designers to work on that push and pull through the system until the optimum solution between design and operational performance is reached.
The idea is to start right from the concept with the architect. There is a sweet spot in terms of user experience and the energy required. The best way to find this is with systems thinking and exploring, from the start of the project, the different design options and how they affect carbon production.
Doug Baldock is Head of Department – High Rise in the UK and Lewis Hunter is an Associate, High Rise in Denmark. They will be presenting at the 2023 Council on Tall Buildings and Urban Habitat Humanising High Density International Conference in Singapore in October. Doug will discuss High Performance – the route to Net Zero, looking at how we can make high-rise buildings as energy efficient as possible, while Lewis will cover Energy and MEP, including embodied carbon and whether as an industry we are doing enough to reduce this.
Want to know more?
Lewis James Hunter
Associate, High Rises
+45 51 61 31 02