How Can I Reach Net Zero with Existing Hospital Buildings?

Healthcare systems are responsible for around 4% of global carbon emissions. In the UK, buildings account for around 15% of the NHS's own carbon footprint, and the NHS has set a target of reducing direct emissions by 80% between 2028 and 2032, before reaching net zero by 2040. Other healthcare systems have different targets and timelines, but the underlying challenge is the same everywhere: most of the buildings responsible for today's emissions are the ones already standing.

Image: Andy Parrett via geograph

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Why existing buildings are the real challenge

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Hospitals and clinics are unlike most commercial buildings. They rely on continuously operating heating, ventilation and other building services to maintain indoor environments that protect patient health and support clinical care. As a result, healthcare buildings are among the most energy-intensive in the built environment.

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While new healthcare facilities are being built with improved energy efficiency, they represent only a small fraction of the building stock. Most hospitals and primary care buildings will remain in use for decades, making existing buildings a defining challenge of healthcare decarbonisation. Therefore, to reach net zero, it’s key to have a better understanding of how today's buildings actually perform, and identify where they can be improved without compromising patient comfort or safety.

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This raises a question: how do you evaluate thousands of existing buildings quickly enough to make informed investment decisions?

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The modelling bottleneck

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The established answer is to build a dynamic simulation model for each building. These models combine information about the building's geometry, construction, technical systems and occupancy to predict energy use and test the impact of retrofit measures before any work takes place.
They are powerful tools, but they are also expensive and time-consuming to produce. Creating one accurate model for a single hospital is a significant undertaking.

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Most healthcare buildings in the UK have an Energy Performance Certificate (EPC). For many of these buildings, the certification process includes an SBEM model that captures key information about the building's geometry, construction and services. These existing models can provide a practical starting point for assessing building performance across large estates, helping identify where more detailed analysis and retrofit investment are likely to have the greatest impact.

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Retrofit has to consider industry-specific challenges

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Improving thermal performance is not always straightforward. Measures such as increased insulation and airtightness reduce heating demand but can also increase the risk of overheating if not carefully assessed.
In healthcare settings, this is especially important. Elevated indoor temperatures can cause patient discomfort, with many UK primary care buildings relying on natural ventilation rather than mechanical cooling.
Building energy models can be used to assess both energy use and overheating risk, allowing retrofit options to be evaluated for their impact on carbon emissions and indoor conditions before they are implemented.

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From individual buildings to estate-wide decisions

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Healthcare organisations are not trying to optimise one building in isolation. They are managing large estates while working towards ambitious carbon targets within limited budgets and timescales.
Making informed retrofit decisions at this scale requires practical ways to assess existing buildings, identify where the greatest opportunities lie, and prioritise investment where it can have the biggest impact.

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xWatts works with healthcare estates to turn building data into practical, evidence-based insights, helping organisations reduce energy use and carbon emissions while maintaining the indoor environments that patients and healthcare staff depend on.

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