HVAC SYSTEMS
deeper understanding of the thermodynamic principles at play, and how technologies interact. To achieve Net Zero, therefore, NHS hospitals must move away from short-term fixes, and instead implement long-term, scalable strategies that integrate: n Heat networks for district-wide efficiency. n Energy storage to balance supply and demand. n Solar PV and renewable electricity to power heat pumps sustainably.
n Waste heat recovery to prevent energy losses.
Cooling has traditionally been seen as separate from heating in NHS buildings, but – Carrier stresses – integration offers a significant opportunity to cut emissions further.
combine these thermal waste streams in a total energy system. This can deliver serious efficiency benefits, but requires a real understanding of system integration and technology interplay. This ‘ambient loop’ approach – where heating and cooling systems are integrated into a shared energy exchange network – offers significant efficiency gains and cost savings. Such integration ensures that every unit of energy used within an NHS facility is maximised, rather than being wasted. For heat pumps to deliver their full decarbonisation potential, hospitals need to take a whole-building approach rather than simply swapping out old boilers for new systems. The NHS has historically adopted a piecemeal approach to energy efficiency, replacing boilers as they fail. However, the transition to heat pumps is not just about swapping technology, but instead about rethinking how buildings and entire estates function. For instance, you can’t just take out a gas boiler and replace it with a heat pump of the same size. NHS estates have changed over time – lighting is now based on LEDs, energy usage has shifted, and what hospitals do inside their buildings has evolved. We need to understand the building’s current energy demand before we change anything. This shift requires a data-first strategy, where hospitals
first analyse: n How energy is used within the building. n How demand has evolved over time. n Where waste energy can be recovered and reused. n How new technologies like heat pumps can be integrated with existing systems.
By reassessing energy demand, improving building fabric, and optimising insulation, hospitals can design heating and cooling systems that match modern requirements, rather than replicating outdated gas boiler configurations.
Boiler replacement and the interplay of sustainable technologies The new focus on managing hospital estates as total energy systems brings to the fore the issue of the interoperability of equipment and systems. Heat pumps do not operate in isolation – they must work with and alongside other sustainable technologies, such as heat networks, waste heat recovery, battery storage, and renewable energy generation. What began as just a boiler replacement scheme and
the installation of heat pumps is now much more than that. It’s about a whole-site approach. This requires a much
68 Health Estate Journal October 2025
This multi-technology, whole building/estate approach ensures that heat pumps do not just replace gas boilers, but operate within a fully optimised, future-proofed system. From this it can be seen that, as the NHS works towards achieving Net Zero by 2040, individual building upgrades alone will not be enough. To reach the necessary scale of emission reductions, the NHS must adopt district-wide solutions that provide sustainable heating and cooling across multiple sites. Heat networks – also known as district heating systems – are one of the most promising strategies for achieving this goal. Heat networks supply heat from a central source to multiple buildings via a network of underground pipes carrying hot water. Instead of relying on individual gas boilers distributed across buildings or estates, NHS facilities connected to a heat network can receive heat from a large-scale centralised source, such as a high-efficiency heat pump, waste heat from industry, or renewable energy systems.
Several key advantages For NHS hospitals, where energy demand is high and 24/7 reliability essential, heat networks offer significant advantages: n Increased efficiency – centralising heat production allows for greater efficiency by reducing energy waste and optimising heating loads across multiple buildings.
n Lower carbon emissions – heat networks enable hospitals to transition away from fossil fuels more effectively, integrating heat pumps and renewable energy at scale.
n Cost savings and infrastructure benefits – by sharing heating infrastructure across multiple sites, NHS Trusts can reduce operational and maintenance costs while avoiding the disruption of replacing individual boiler systems in each building.
A heat pump-based heat network takes this concept a step further by using a large-scale heat pump as the primary heat source. Instead of each building relying on its own gas-fired heating system, a central heat pump extracts heat from the air, ground, or water, and distributes it efficiently across a network of connected buildings. A standalone heat pump constantly ejects hot air back
into the atmosphere as part of its process – just like an air-source chiller expels heat. Operating as part of a heat network, however, that waste heat produced can be captured and reused efficiently. Instead of wasting energy, the system balances heating and cooling loads to maximise efficiency. This energy ‘recycling’ approach ensures that waste heat from cooling systems can be repurposed to support heating demands, making the entire network more efficient and sustainable. For NHS estates, heat networks provide a scalable and future-proof way to transition away from fossil fuels. However, the size and design of the network play a crucial role in maximising efficiency. To give an illustration of the principle in relation to residential homes: If you take 100 houses, each with a six kilowatt boiler, that’s 600
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184
