June 20th 2024

Retrofitting buildings: The role of energy modelling

Retrofitting buildings: The role of energy modelling

Retrofitting buildings for increased energy efficiency will be key to achieving net zero carbon targets. Particularly considering that 80% of the buildings that will exist in 2050 are already standing today.

Recent studies have highlighted the significant energy savings potential of retrofit projects. However, making upgrades can be a costly. In some cases, three to five times higher than it costs to design measures into our new buildings from the outset.

Building owners therefore need to be confident that retrofit measures will deliver on their expectations. Particularly in reducing their building's energy consumption, carbon emissions and costs. However, they also need to ensure upgrades will not have any unintended consequences upon other areas of their building’s performance. For example, issues relating to overheating or poor ventilation.

This is where energy modelling can play a crucial role in helping to de-risk building retrofits. Helping to inform and verify which measures will perform best in the context of any given building.

What is Retrofitting?

Retrofitting refers to the process of updating existing buildings to improve their energy efficiency and performance. Common measures can include:

  • Fabric Improvements: Enhancing the thermal envelope of a building to prevent heat loss. Upgrades may include insulation or window upgrades.
  • Lighting Upgrades: Replacing light fittings with energy-efficient alternatives, such as LEDs.
  • HVAC Upgrades: Upgrading or modifying existing heating, ventilation, and air conditioning (HVAC) systems.
  • Heat Pumps: Systems that transfer heat, from the outside air or ground, and increase the temperature to provide a low carbon heating solution.
  • Solar Panels: Installing photovoltaic systems to generate renewable energy on-site.

Projects typically fall into one of the following categories:

  • Proactive Reuse: Involves making repairs and upgrades to an existing building to improve its performance.
  • Adaptive Reuse: Repurposing existing buildings to meet new needs and uses.
  • Expansive Reuse: Extending/adding new space to existing buildings to increase their value.

The Benefits of Retrofitting

Retrofitting offers a wide range of environmental, commercial and social benefits. These can include:

Energy Savings

Upgrades such as enhanced insulation, improvements to building services, and renewable energy installations can drastically reduce energy consumption. Creating buildings which are much more efficient to run.

Cost Savings

Building upgrades can lead to long-term cost savings as a result of lower energy bills and maintenance costs. In many cases, retrofitting can be substantially more cost effective than demolishing and rebuilding from scratch. Some upgrades may also qualify for tax incentives and grants, to help justify the upfront costs.

Carbon Savings

Reducing energy consumption directly reduces operational carbon emissions. However, it is still crucial to adopt a whole-life carbon approach to retrofit projects. This ensures that the embodied carbon impacts do not outweigh the savings achieved in operation. However, in many cases, retrofitting will still result in significantly lower greenhouse gas emissions overall, when compared to rebuilding.

Creating Value

Enhanced property values, increased economic output, and jobs creation are significant commercial benefits of retrofitting. Upgraded buildings are more attractive to tenants and buyers, and the process itself can stimulate local economies.

Improving Health & Wellbeing

Energy efficient buildings, if done right, can also provide better indoor air quality and optimised comfort conditions for occupants. Contributing to overall health and wellbeing.

Making Good Retrofit Decisions: The Role of Energy Modelling

Energy modelling tools can play a critical role in informing retrofit strategies for existing buildings. By simulating the impact of different retrofit scenarios, energy modellers can assess the benefits, and potential drawbacks, of different strategies. Helping to map out the most sustainable, cost effective interventions for building owners on the route to net-zero.

Our integrated suite of tools make it possible to understand the whole building impact of different retrofit scenarios. Providing comprehensive assessment across all aspects of energy, carbon, cost, and comfort. Meanwhile, our integration with OneClickLCA, supports a whole-life carbon approach, enabling consideration of both the embodied and operational carbon impacts within the same model.

Following implementation of retrofit measures, our IES Live platform can support ongoing M&V style tracking. Helping to verify energy, carbon and cost savings and that systems continue to perform optimally over time.

Retrofitting Buildings: Case Study

Results comparison of building retrofit strategies

IES recently developed a digital twin of three social housing blocks in Dublin to assess the whole-life carbon impact of four retrofit strategies. The study considered the total emissions across three time periods, aligned with national targets for 2030, 2050 and beyond. The project discovered that deep retrofit could achieve up to an 85% reduction in emissions, over a 60-year period. Highlighting the value of energy models in guiding the most effective retrofit strategies, considering a whole-life carbon approach.


In summary, energy modelling is invaluable for making informed retrofit decisions. It ensures that retrofit measures are effective, sustainable, and economically viable. By leveraging advanced modelling technologies, we can maximise the benefits of retrofitting and contribute significantly to our low-carbon future.

Check out our retrofit optioneering modelling services or get in touch with our team to learn more.