To be bylined to Don Mclean, CEO at global climate tech firm, IES.
Don Mclean, CEO of IES, discusses the technologies that are transforming retrofitting efforts
The World Meteorological Organisation (WMO) recently declared 2024 as the hottest year on record. The escalating impact of climate change is becoming more evident by the day. From extreme weather events and resource scarcity to rising energy insecurity, the need for meaningful action has never been more urgent.
As a major source of greenhouse gas emissions – responsible for almost 40% of the global total – the built environment possesses immense potential to curb future harm to the planet. Therefore, the sector must undergo a profound green transformation by designing better buildings and retrofitting those we already have to meet critical net zero targets.
Retrofitting technology is a necessity for a decarbonised world
With more than 70% of today’s buildings expected to still be in operation by 2050, retrofitting is not just an option but a necessity if we are to improve energy efficiency and reduce carbon emissions.
Typically, retrofitting existing buildings results in 50–75% fewer emissions compared to demolishing and rebuilding. Yet, retrofitting at scale remains a major hurdle. The current global retrofit rate stands at just 1% of building stock per year – far short of the 3% annual rate required to meet climate targets. We need to increase the rate at which we retrofit while avoiding a ‘one-size-fits-all’ approach, which can result in misguided and costly measures being implemented with no real impact, given each building comes with unique characteristics, operational needs and constraints. Without a tailored approach, retrofitting efforts risk wasting time, money, and resources.
This is where digital twin technology, advanced energy modelling, and dynamic simulation tools can transform the built environment’s decarbonisation journey. These technologies enable building owners, designers, and operators to create flexible, targeted retrofit plans based on a building’s specific context and the reality of its operation. They not only inform the initial optimum retrofit strategies but can continue to deliver value throughout a building’s lifecycle, ensuring ongoing operational efficiency and environmental performance.
Why a ‘one-size-fits-all’ approach to retrofitting won’t work
No two buildings are the same. A building’s age, geographical location, physical structure, existing equipment, occupancy patterns and local climate conditions, can influence which retrofitting strategies will be most effective. As highlighted in IES’s Energy Modelling for Retrofit white paper, building retrofits, particularly for large, complex buildings, must be modelled in context. Generic, ‘off-the-shelf’ retrofit measures rarely deliver optimum results because they overlook a building’s unique energy-use profile and operational realities.
By contrast, a tailored, strategic retrofit, developed through robust digital simulation, can identify which upgrades will perform best for a specific building – all before any physical work begins. Retrofitting measures can include improved insulation, advanced heating systems, and energy-efficient lighting, among others. By using digital simulation tools, the risk of measures underdelivering – or worse, causing other negative impacts on the building, such as overheating – is significantly reduced. This means investments can be strategically directed towards the most impactful solutions.
It’s also worth pointing out that retrofitting in itself is not an isolated solution. A building’s performance changes over time based on factors such as occupant behaviour, climate, occupancy rates, and evolving energy demands. Only a bespoke approach, guided by ongoing data collection, performance monitoring, and analysis, can ensure that retrofits remain effective throughout a building’s lifecycle. Without continuous performance monitoring and adjustments, even well-executed retrofits can fall short of their potential. These factors, along with the growing unpredictability of the climate, make it clear why continuously monitoring a building’s performance and implementing ongoing retrofits are essential to keeping it resilient and efficient.
How digital twins can maximise retrofit impact
The effectiveness of modern retrofit strategies can be turbocharged by digital twin technology – virtual replicas of physical buildings that enable advanced performance analysis. These dynamic models combine real building data with physics-based simulations of how various systems, such as heating, ventilation, and lighting, interact with the whole building under real-world conditions.
By combining these simulations with real-time data from sensors, meters and building management systems, digital twins offer granular insights into a building’s energy usage. This allows project teams to make data-driven decisions rather than relying on vague assumptions. For example, while traditional approaches might prioritise window upgrades for energy savings, a digital twin might reveal that addressing ventilation inefficiencies would have a faster payback period and a greater impact on carbon reduction.
Ultimately, digital twins ensure that every pound spent on retrofit activity delivers measurable benefits and is spent in an optimal way. They enable building owners to forecast return on investment (ROI) for each potential action, prioritising interventions that align with both sustainability goals and financial constraints.
The key barriers to large-scale retrofitting and how to overcome them
Despite the clear benefits, scaling retrofits across entire building portfolios presents significant challenges. One major hurdle is data availability and quality – particularly for older buildings that often lack accurate records of their systems and operational demands. Without this information, it is difficult to develop effective retrofit strategies. To overcome this, AEC consultants should undertake detailed building surveys and deploy smart monitoring technology to gather reliable, real-time performance data.
Budgetary constraints can also pose a significant challenge. While retrofits deliver long-term cost savings, the upfront investment can be prohibitive. This is where digital simulation plays a crucial role, enabling stakeholders to justify spending by demonstrating tangible cost savings through robust energy modelling. Additionally, prioritising optimisation, aided by the digital twin, as a first step prior to implementing any retrofit measures can further unlock significant operational energy savings, which can be reinvested into deeper renovations or upgrades. An optimisation-first approach will also ensure the impact of any subsequent retrofit measures are maximised and not fighting against an already inefficient building.
Additionally, occupant disruption and operational downtime can deter retrofit activity, particularly in commercial or hospitality settings. Digital twins can help mitigate this by allowing project teams to plan retrofit activities around building usage patterns, ensuring work is carried out with minimal impact on day-to-day operations.
The future of retrofitting
As climate targets tighten, energy costs continue to rise, and the real-world impacts of climate change come to the fore, retrofitting the built environment will only grow in importance. Yet achieving meaningful impact will require a holistic, data-led approach that respects each building’s originality. Digital twins, underpinned by advanced energy modelling and real-time performance data, will remain crucial in guiding these efforts.
From supporting evidence-based decision-making at the project outset to ensuring upgrades continue delivering results long after implementation, simulation-driven tools represent the future of sustainable building management. The path to net zero lies not only in faster retrofitting but in smarter retrofitting. By embracing technology and tailoring interventions to each building’s specific needs, the built environment can deliver lasting environmental and economic benefits.
