Warrington digital twin

A virtual Warrington revealed how much different levels of retrofits would cost across the borough. Credit: IES

Case study

How one UK town used digital twins to model retrofit costs

Warrington, a town in the northwest of England, teamed up with climate tech experts at IES to understand the cost of retrofitting the city’s buildings and help it achieve its net zero targets.

As part of an Innovate UK-funded project called REWIRE, Warrington Borough Council, which declared a climate emergency in 2019, worked with charity Pure Leapfrog and IES to create a digital twin of the area.

Combining various data sources from the council, the Energy Performance Certificate database and local distribution network operators, the digital twin helped identify the energy, carbon and cost-efficiency measures required for the town to decarbonise.

IES said the models it created are “easily replicable” in any UK city and hold a huge amount of potential in helping the country make progress towards net zero.

How it works

Data about 29 separate areas of the borough – including EPC data on 50,000 homes, building geometry, use and age, characteristics and electric network infrastructure – fed into IES’s masterplanning tool Intelligent Community Design.

ICD analyses and monitors how the community may evolve over time and tracks the environmental impact of any changes such as population growth, the installation of renewable energy systems and changes to the massing and form of buildings.

These 29 models were then collated into a single digital twin hosted on IES’s Intelligent Community Information Model platform.

IES used this to create archetype models for four types of homes: detached houses, semi-detached houses, terraced homes and apartments. These models were used to create a holistic view of the area, integrating electricity, heating, cooling, waste heat networks and shared energy links across buildings.


With these data sources collated and buildings modelled, the project considered the costs of three levels of retrofits:

  • Basic – cavity wall and loft insulation
  • Intermediate – basic, plus solid wall insulation
  • Full retrofit – upgrading buildings to standards set out in Part L of the Building Regulations 2013 (e.g. floor insulation, improved glazing, reduced infiltration rates of outside air).

Warrington was able to work out the cost of retrofitting each neighbourhood. The estimated costs were:

  • Basic – £500,000, saving £77,000 in annual energy costs across 500 buildings and paying itself back in six and a half years
  • Full – £5,000,000, saving £180,900 in annual energy costs and paying for itself in 30 years.

However, IES said: “These payback times represent energy costs at the time of the work being carried out, which have since seen a significant increase, meaning that payback time for retrofit measures would be greatly improved since then.”

Taking results one step further

Using the results for the three retrofit scenarios, the project could simulate different approaches for full decarbonisation of the district, finding optimal solutions for cutting emissions in each of the 29 neighbourhoods.

The measures identified were: the installation of domestic and commercial air source heat pumps and district heating, domestic PV with battery storage and the installation of electric vehicle charging infrastructure.

Optimal strategies depended on specific criteria, such as the most prevalent built form and construction materials and availability of off-street parking.

In one neighbourhood, the basic retrofit, following the installation of district heating, air source heat pumps and mass PV and community storage, would result in a 41% annual energy cost saving, worth £583 per household.

The maximum retrofit scenario along with the same interventions would see a 56% reduction in energy costs per year, equivalent to £795 per household at the time the simulations were run in 2020.

Total cost of retrofits

The overall cost of the interventions totalled £2m-£5m per neighbourhood depending on the retrofit scenario, but this did not take into account district heating systems, domestic heat pumps or EV chargers, which could all add to costs significantly.

Using the digital twin simulation of two neighbourhoods within the borough, the project demonstrated that once all interventions were applied, an annual saving of 2,000-2,500 tonnes of CO2 would be possible.

This would result in both these neighbourhoods becoming net zero with only “a very small amount” of carbon offsetting required, IES said.

Fergus Ross, ICL project manager at IES, said: “These models are easily replicable to any UK city and hold a huge amount of potential in bolstering the country’s progression towards net-zero, so we really hope to see more councils implementing this kind of technology.”

Janet Henshaw, Warrington Borough Council cabinet member for sustainability and climate change, said: “A shared central database and interconnected tools have allowed data and analysis to be easily shared between key stakeholders within this project, laying out some pathways for potential future decarbonisation.

“Using the model to full effect will allow the council to see various possible optimisation scenarios and understand the potential return on investment for associated decarbonisation initiatives.”

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