How can the NHS get the most out of its existing buildings?
Around 80% of the buildings the NHS will operate in 2050 have already been built. Almost a fifth of the estate predates the NHS itself, and 43% of it is over 30 years old.That single fact should reframe how every net zero conversation in the sector starts. The estate that exists today is, overwhelmingly, the estate that has to get to net zero. The energy efficiency standards of new-builds are very important, but enhancing existing buildings is key to moving the needle to net-zero.The scale involved is hard to overstate. In 2020 the NHS became the world's first health system to commit to net zero. It's also the UK's largest single public energy user, supplying energy to over 13,500 buildings across 27 million m². The annual energy bill for trusts alone has nearly doubled since 2019, to more than £1.4 billion.
Reaching Net Zero through existing buildings
- Reducing operational energy intensity (kWh/m²/yr)
HVAC typically accounts for 45–55% of total energy use in hospitals and 50–60% in outpatient facilities.A major issue is that most trusts can’t even see the energy they are wasting, therefore improving monitoring and visibility is a key first step in making existing plants more energy efficient. Having visibility at the system and plant level through submetering can help identify the most wasteful areas of the building.The importance of BMS optimisation cannot be overstated. Healthcare facilities that implement building management systems commonly achieve 20–30% energy savings, plus 10–20% lower maintenance costs through predictive maintenance. Refining schedules and set points, which reduce needless after-hours building maintenance, can reduce energy usage by 10-20%. Scaled up from individual buildings to large trust sites, BMS optimisation can deliver huge cost savings.
- Improving carbon intensity (kgCO2e/m²/yr)
kWh/m²/yr measures how much energy a building uses. kgCO2e/m²/yr measures the carbon cost of that energy, which depends on the fuel source as much as the volume. A building can hold its kWh/m²/yr flat and still cut kgCO2e/m²/yr sharply just by switching from gas to grid electricity, because the two fuels no longer carry the same carbon cost per kWh in the UK.Electrify heat, don't just insulate it. Gas supplies 74–87% of NHS estate energy. Switching heat sources from gas boilers to heat pumps is the single biggest carbon-intensity lever available on an existing healthcare estate.
- Reducing embodied carbon (kgCO2e/m²), upfront and across lifecycle
Choose refurbishment over rebuild wherever the space allows it. The NHS Net Zero Building Standard explains that: for embodied carbon, the greatest impact intervention is to build nothing, or build less. Upfront carbon and raw material use in a major refurbishment is typically far lower than a new build, simply because some building elements are retained rather than replaced.Existing buildings also come with fixed characteristics, orientation, form, grid geometry, storey heights, that shape their energy use intensity and operational carbon regardless of what's done to them, so those trade-offs still need weighing case by case.A vision for NHS Net ZeroFour things follow from all of this, in order of where the leverage sits:Operational energy intensity is the main driver. Improving kWh/m²/yr through better control, maintenance and optimisation of existing plant delivers measurable reductions without any new construction.Carbon intensity improves when systems run efficiently. HVAC often accounts for nearly half of hospital energy use, so optimising performance and monitoring consumption directly reduces kgCO2e/m²/yr.Refurbishment is often the lower-carbon pathway. Major refurbishment projects typically use significantly less upfront carbon than new builds. Passive upgrades, wall insulation, window and frame replacement and solar shading, meaningfully reduce primary energy demand and improve internal comfort at the same time.Getting the existing estate to work harderMost of what net zero requires from the NHS estate isn't a construction project. It's making 13,500 buildings run the way they were designed to, with visibility that doesn't currently exist across most of that stock.xWatts Intelligence gives estates teams greater visibility at system and plant level, so that wastage gets caught. xWatts Automation then takes the same data and adjusts set-points in real time, closing the gap between design intent and actual operation.If you want to know more, talk to our team. (edited)
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