Digital twin project to optimise renovation of social housing

IES and Dublin City Council won the Green Collaboration Award at the Green Awards 2024 earlier this year for their work together on a whole-life carbon digital twin project designed to optimise the renovation of social housing. It developed the digital twin of three social housing blocks in Dublin and assessed the whole-life carbon impact of four retrofit strategies over three time periods aligned with national targets for 2030, 2050 and beyond. Colin Griffioen (pictured right), Business Development Consultant, IES, explains how IES went about it and the conclusions drawn.

Using its digital twin technology, IES carried out modelling of three residential blocks located on Lower Dominick Street, Dublin. It assessed the full carbon impact and efficiency of four renovation strategies, over three different time periods, to regenerate the vacant buildings built in 1962. The strategies align with the council’s climate targets for 2030, 2050 and beyond.

The project took a whole-life carbon approach, taking into account both embodied and operational carbon. Consideration of embodied carbon, which is the emissions associated with construction and materials throughout the whole life-cycle of a building, is a critical part of sustainable building analysis that is regrettably often overlooked.

The digital twin models were used to identify which strategy, from shallow retrofit to demolition and rebuild, would result in the biggest reduction in wholelife carbon emissions. To determine the strategy that would lower emissions most significantly, the main sources of energy consumption were identified by calibrating data from existing energy bills of the social housing site.

The strategies were as follows –

• Strategy 1: Shallow Retrofit (the implementation of one or two measures which resulted in a reduction in energy consumption of between 0% and 30%);

• Strategy 2: Medium Retrofit (3-6 improvements with a reduction of 30% -60%);

• Strategy 3: Deep retrofit (a package of measures working together leading to an energy reduction of 60%-90%);

• Strategy 4: Reduce to Core and Shell and Rebuild (leaving in place structural elements and the upgrade of all other elements which have a bearing on energy use in addition to the installation of renewable technologies in order to reduce energy and CO2 levels to close to zero).

Each strategy consisted of a package of energy efficiency measures. IES’ core Virtual Environment (VE) software was used to understand the impact on energy usage and operational carbon of each measure through dynamic, physicsbased simulations. This allowed them to understand which strategy would bring the biggest reduction in operational emissions, which, as expected, was Strategy 4.

In order to understand the wholelife cycle impact of the interventions, the integration between the VE and

OneClickLCA was used to calculate the embodied carbon associated with each intervention. Once this was added to the operational emissions, and estimated at different life periods (20, 40 and 60 years), Strategy 3 outperformed Strategy 4 due to the high embodied carbon associated with a full renovation. Strategy 3 (Deep Retrofit) was hence selected as the best option to optimise the whole-life carbon of the building over all life-cycle periods assessed. The full results are included in the Dublin City Council Climate Resilient Housing Report, which highlights that over a 60year life period, each residential block can achieve around an 85% reduction in cumulative emissions by carrying out a deep retrofit. As a result of the study, Dublin City Council can make evidencebacked decisions when developing the most optimal whole-life carbon regeneration strategy for the refurbishment of ageing social housing buildings. The project was funded by the Department of Public Expenditure and Reform’s Public Sector Innovation Fund, with IES and DCC in partnership winning the contract to create the digital twin. The results of the project will help Dublin City Council to meet emissions reduction targets, retrofitting targets for social housing, and housing delivery targets. As more targets are imposed by the government to mitigate climate change, new systems must be developed to assess the strategies for derelict buildings.

Sabrina Dekker, Climate Change Coordinator, Dublin City Council, said: “This project has demonstrated the results that can be achieved through working collaboratively, exchanging knowledge to drive innovation and to meet targets. IES’ digital twin technology has helped us confirm the importance of retrofitting to reduce our emissions and the results will be used to inform future projects. It is also hopeg that the study can be scaled to more sites across Dublin and beyond to estimate the carbon impact of other renovation projects.”