Explainer: Retrofit

The UN forecasts that the world’s population will rise by 2bn to 9.7bn by 2050. With growing numbers of people and limited resources, our infrastructure requirements will increasingly need to be met by existing assets rather than new ones. Meeting net-zero targets and limiting global temperature rises also means a lot of attention is being paid to reducing the carbon emissions of existing assets to ensure they are fit for the future.  

Retrofitting homes and commercial properties receives a lot of attention as domestic energy consumption accounts for significant proportions of total energy budgets and carbon emissions.

The mayor of London has produced the report Design for a Circular Economy, which turns the practice of ‘demolish first’ on its head and promotes refurbishment across the capital, with a particular focus on buildings. The graphic below shows how London is attempting to transform its current, linear practice into circular practice.

Alongside buildings, there is a growing focus on retrofitting infrastructure and public assets to extend their life and to make better use of the built environment. 

New investments may often be more cost-effective than replacing or restoring ageing infrastructure. However, retrofit will often make financial and environmental sense as it avoids large capital investments while minimising the disruption and carbon involved in new construction. 

Roger Bareham, technical director at consultant Hydrock, says retrofitting is especially important to protect historic assets: “Refurbishment can bring old assets back to life and it would be wasteful to release their carbon into the environment, so why not re-use the asset?” 

Andrew Howe, associate director at Heyne Tillett Steel, says that typically the initial approach has been to start anew, but that “we’ve got to start flipping this". He adds: "We need to start looking at what we can salvage and repurpose, and how we refurb assets.” 

This approach is already being used on the UK’s railway networks. “While this is often more expensive, we’ve always used a ‘demolition as a last resort’ approach and try to sensitively repair structures to maintain their cultural heritage,” says Hélène Rossiter, head of the historical railways estate programme at National Highways.

One of the many challenges for the proponents of retrofit is that it can be easy to overlook the potential in existing assets. Environmental issues and targets are changing this approach, but clients need to be presented with opportunities to start changing their perceptions. 

“We must challenge ourselves first,” Howe says. “Why are we demolishing or removing something? Is there a better way we can retrofit or refurbish? If we need to take something down, can we disassemble the parts and make them into something else?” 

Understanding how an existing asset ‘works’ is one of the keys to a successful retrofit. All projects can be retrofitted in theory, but it might become uneconomical to go to a certain level of intrusion.

For example, on the Union Chain Bridge in Northumberland, more than 10,000 parts of unknown condition had to be recorded. “You can spend a lot of money doing surveys and so on, but you’re never going to know the condition of things until you pull them apart,” says Simon Rudman, technical services design manager at Northumberland County Council. 

While economics still remain a key priority for most clients, choices are increasingly being made for environmental benefit.

Further challenges to retrofit projects are shown in the graphic below:

Collecting data about an asset can be hugely beneficial during a retrofit project and over its life. Whether it is a QR code on a column or using in-built sensors to check for movement, digital technology can provide many benefits for projects. 

“Digital engineering can make documenting, operating, inspecting and maintaining assets easy and cost-effective,” says Ayanangshu Dey. “A major reason for new-builds is a lack of authentic data on existing assets, and the time and resources needed to generate this.” 

BIM (building information modelling) is the digital advance most commonly used – not only when creating a model to help document the refurbishment of an asset, but also when further work is needed years later. Still, asking clients to pay for BIM when much of the benefit will be felt in the future can be a challenge for engineers. 

A 2018 report by the ICE Skills Review Group found that adopting digital technology was a key trend affecting skills. Workforces may therefore need training to gain the digital skills needed for retrofit projects. 

Being inquisitive and spending time onsite to understand an asset are also important when it comes to making a success of a retrofit project. Ask questions such as: where are the load paths? What happens if we remove a column? What grades of steel have been used? 

“Even simple structures like bridges have behaviours that may not be intuitive – that’s why training is crucial before every key stage,” says Neil Hewitt, project director at Spencer Group, who worked on the Union Chain Bridge. “Don’t have preconceived ideas about how work will progress – always have a Plan B, C and D.” 

People skills and soft skills are also critical for successful retrofit projects. “We must consider the range of opinions and be sensitive to non-engineering views,” says National Highways’ Hélène Rossiter. “There’s a clear need for good and strong stakeholder engagement and management.”  

Historically, cost has been the main driver in retrofit versus new-build decisions. However, assessing the carbon impact of a project is becoming much more important and can help when making the case for retrofit-first to clients and project teams.

While there are many reasons for resistance to retrofitting, Ayanangshu Dey says these can be overcome: “Engineers need to advocate retrofitting by identifying these reasons and then addressing each from a retrofit-oriented mindset.” 

Rossiter says advocating retrofit can be done “by involving stakeholders early, gathering views of interest groups, using case studies to show the benefits and ensuring asset management approaches prioritise elements other than just cost”. 

Every retrofit project has challenges but accepting them and finding innovative solutions can reap rewards, says Heyne Tillett Steel’s Andrew Howe. “There’s something incredibly satisfying about unlocking the potential value in an asset," he says. "We have a great engineering history. From looking at old maps to using a low-carbon design, there’s something about the journey that is quite special.”