Paul Marsden, Public Health Technical Specification manager at Baxi, and Chair of the Society of Public Health Engineers (SoPHE) Industry Working Group, discusses the challenges and opportunities for NHS Estates and Facilities managers surrounding the decarbonisation of domestic hot water. He argues that the high hot water demand frequently associated with healthcare premises makes it a clear focus for reduction in associated energy use and emissions
One of the largest health systems in the world, with a vast estate, including hospitals, clinics, and other healthcare facilities, the NHS is a significant energy consumer, estimated to account for 4-5% of the UK’s total carbon footprint.1 The impacts of climate change represent one of the biggest public health challenges of this century, requiring health services to adapt to respond to new and increased health risks. As part of its commitment to tackling climate change, the NHS has set ambitious targets for reaching Net Zero from its directly controlled emissions by 2040, and the emissions it can influence by 2045. In so doing, it aims to become the world’s first Net Zero national health service. Reducing carbon emissions from hot water generation is one of the areas identified for achieving this target
The high hot water demand frequently associated with healthcare premises makes it a clear focus for reduction in associated energy use and emissions. However, it is one that comes with certain challenges – from the scale of the estate, to the huge variety of building types and hot water systems, to the specific considerations relating to domestic hot water (DHW) provision in these hygiene-critical environments.
In this article, we will discuss the particular requirements for hot water in hospitals and healthcare buildings, the challenges for estates and facilities managers in delivering reliable, sanitary hot water with reduced emissions, and the opportunities for improving the energy efficiency of hot water systems across the NHS estate to drive down its carbon footprint.
Halting climate change
In March this year, the United Nations Intergovernmental Panel on Climate Change (IPCC) published its latest report on climate change, and what must be done to solve it. The message from the scientists was unequivocal – the pace and scale of action must speed up if we are to halt climate change, and requires ‘rapid and deep and, in most cases, immediate greenhouse gas emissions reductions in all sectors this decade’.2 This sentiment was echoed in a new report3 by the Climate Change Committee on the pace of the nation’s adaptation progress to climate change
The UK government set a target of achieving Net Zero emissions by 2050 (2045 in Scotland). The NHS has a more ambitious goal, committing to achieving carbon neutrality by 2040, a target that requires significant action to reduce energy consumption and carbon emissions. Reducing hot water generation is an essential part of this effort, as hot water is one of the most energy-intensive processes in healthcare facilities.
The Health and Care Act
On 1 July 2022, the NHS became the first ever health system to embed Net Zero into legislation through the Health and Care Act 2022.4 This places duties on NHS England, and all NHS Trusts, Foundation Trusts, and Integrated Care Boards, to contribute towards statutory emissions and environmental targets. Why the earlier target? The health service accounts for 4-5% of the UK’s total carbon footprint, and the NHS in England is responsible for 40% of the public sector’s emissions.5 As such, it has an important role to play in reducing carbon emissions, and the impact from taking immediate action to cut emissions and improve the sustainability of its operations will be significant.
The NHS is also driven by its mission to improve the nation’s wellbeing, and become more resilient to manage the accelerating effects of climate change on public health. Nine out of the 10 hottest years on record happened in the last decade, with almost 900 extra deaths6 caused by the summer heatwaves of 2019, according to Public Health England. The NHS believes that taking action to reduce carbon emissions would bring direct benefits to public health. Following a Net Zero pathway, it estimates, will see 5,770 lives saved per year from reductions in air pollution alone.
World’s first Net Zero national health service
The NHS has formally adopted two targets to achieve its ambition to become the world’s first Net Zero national health service, set as the earliest possible credible dates to achieve Net Zero emissions. The first, for the NHS Carbon Footprint (emissions under direct control of the NHS), is to achieve Net Zero by 2040, with an ambition for an interim 80% reduction by 2028-2032. The second is for the NHS Carbon Footprint Plus, (including the NHS’s wider supply chain), which sets a target for Net Zero by 2045, with an ambition for an interim 80% reduction by 2036-2039.
The NHS has reduced its carbon footprint considerably in the last 10 years, with an estimated 62% reduction in emissions from 1990 to 2020, and an approximate reduction of 26% in the wider Carbon Footprint Plus.1 However, clearly, considerably more work remains to be done.
Significant opportunities have been identified to reduce emissions from energy use in buildings, waste, and water, and to transition to new sources of heat generation. Given the high demand for hot water that is frequently associated with healthcare premises – from comfortable conditions and catering to in-house sterilisation and laundry – this service is a clear target for efficiency improvement and emissions reduction. However, it’s one that comes with certain challenges for NHS Estates and Facilities managers.
Unique requirements
In no other environment is access to an efficient and sanitary supply of water more important than in healthcare. Ensuring an adequate, reliable hot water supply is key to the whole operation, creating comfortable conditions for patients and staff, and maintaining clinical standards, as well as being essential for treatment purposes
Hospital hot water distribution systems are highly complex. Their design and function must ensure that water is adequately stored, cycled, and distributed to prevent a build-up of harmful bacteria. Preventing the risk of bacterial build-up (mostly related to the control of Legionella bacteria in water systems) is of particular concern, due to the ability of a large number of different microorganisms, biotoxins, and other contaminants, to cultivate in water
The Health and Safety Executive (HSE) advises that hot water should be stored at least at 60 °C, and distributed so that it reaches 55 °C at point of use in healthcare premises to reduce the risk of Legionella. 7
Associated with this is the need to avoid the risk of scalding and burns, particularly for the protection of vulnerable patients. Temperature control will need to be provided at hot water outlets used by persons at risk of being scalded. The British Health Technical Memoranda HTM 04-018 (SHTM 04-01 in Scotland and WHTM 04-01 in Wales) set out best practice to keep hospital water supplies in a safe, clean, and hygienic condition.
Further statutory guidance to support hospital Trusts in achieving the Net Zero ambition is set out in the Delivering a ‘Net Zero’ National Health Service report. 1 Best practice guidance helps stakeholders – including Estates and Facilities managers, suppliers, and NHS management personnel – to mitigate the risks associated with the large, complex systems found across UK hospitals, clinics, and surgeries.
The scale of the challenge The vast scale of the NHS estate, the diversity of buildings, and the differing heating systems within the NHS estate, add to the complexity of the challenge. Certainly, new hospitals and NHS buildings will be designed to require less heat for operational use, and to be optimised for a decarbonised electricity grid. In buildings like these, a fully electric approach to DHW based around renewable solutions, such as heat pumps and direct-fired electric water heaters, is likely to be the favoured approach.
However, these new hospitals are just the tip of the iceberg, accounting for less than a fifth of the secondary NHS care estate. It’s the older stock that is the real challenge. The reality is that transitioning a huge hospital premises from gas-powered steam or high temperature water heating systems to a low-carbon solution can be a hugely complex task for Estates and Facilities managers.
The same applies to the primary care estate, with its 7,000 GP practices in England, spread across 9,000 buildings, many of which currently rely on high temperature heating systems for heating and hot water provision. Moving to a low carbon system will likely require careful planning and budgeting – as well as support from heat experts.
Identifying the financially and technically feasible
Identifying the financially and technically feasible opportunities to drive down emissions from DHW in these buildings can be daunting. However, while there can be no silver bullet solution, there are numerous opportunities to achieve more sustainable, energy-efficient hot water generation across healthcare premises. The focus should be on reducing operational energy usage and increasing renewable energy supply where possible, all the while prioritising safe water. With this in mind, let’s explore some of the options.
Energy efficiency
The first step should always be to identify and act immediately on any opportunities to reduce energy demand. Energy efficiency is critical, because it lowers energy consumption and associated emissions and costs. The cleanest and cheapest kWh of energy is, after all, the one we don’t use. Where hot water is concerned, quick wins might include switching to low volume shower heads and taps to lower water and energy usage, or adding lagging to pipework to reduce heat losses
In buildings where a central boiler plant and calorifier provide both heating and hot water, separating out the hot water is advisable to avoid unnecessary energy use. Heating is typically only required from autumn through to spring, and is needed constantly while the building is occupied. Hot water is an annual requirement, and required each day that the building is in use. However, there are peaks and troughs in demand for hot water throughout the day
For this reason, it is senseless to generate these two very different requirements from a single source. Having dedicated plant for each means that the chosen technology can be sized more closely, and, therefore, accurately, to meet the specific requirements for each building. This makes more effective use of energy, and opens up the ability to site direct electric or direct gas-fired hot water equipment at – or very close to – point of use. Another option to improve energy efficiency might be to upgrade any non-condensing direct-fired water heaters to more energy-efficient condensing models to drive down energy consumption and emissions
Heat pumps
For the larger task of replacing the heating system, air source heat pumps (ASHPs) are widely viewed as one of the favoured technologies to decarbonise heating and hot water across the NHS estate. Using refrigerant technology to heat domestic hot water is an attractive proposition for reducing associated emissions, as the potential efficiency of air source heat pumps can be up to 400% in many cases. This means that for every 1 kWh of electricity used to run the heat pump, you get up to 4 kWh of heat output. Certainly, in newer buildings, heat pumps will play a key role in achieving low carbon hot water. It can, however, be more challenging to make older hospitals benefit from an ASHP solution. Converting large existing hospitals that use gas-powered steam or high temperature water heating systems to a low-carbon solution, for example, will typically need to be carried out in several stages
Available space, time, and budget will be some of the factors that should be considered at the outset. The electrical capacity of the site will be a further consideration when switching to electrical heat, especially where EV charging points are in place. Putting a clear roadmap in place – identifying the overarching goals, the available time to complete the work, the budget and any funding opportunities – will make it possible to plan out and design the various stages of work. Experienced manufacturers and heat experts will be able to advise on the available options, as well as the latest technologies and designs to help Trusts plot the most appropriate decarbonisation pathway for their individual estates.
High and low temperature heat pumps
When considering DHW generation, there are a number of ways in which ASHPs can be used. Let’s consider possible ASHPs’ design strategies using different types of heat pumps – low temperature and high temperature. Low temperature ASHPs can be used with direct electric or direct gas-fired solutions to raise the DHW to safe temperatures. The direct electric approach is more likely to be the option of choice, but would involve higher volumes of stored DHW – certainly compared with low-storage direct gas-fired water heaters, which the building may previously have relied on (see Figure 1).
If considering this solution, it’s important to consider potential issues relating to available space and weight for the larger cylinders – particularly when dealing with rooftop or non-basement plant rooms. Controlling Legionella within the larger volumes of stored water will also need to be carefully monitored and managed.
High temperature ASHPs are capable of delivering the high flow temperature required to meet the design temperature for sanitary hot water. The advantage of using HT heat pumps is that it avoids the need for an alternative form of technology to store the DHW above Legionella temperatures (60 °C or higher). This makes it a truly low-to-zero carbon solution.
This option also offers greater design flexibility, and requires less space, for a much simpler design, and easier installation. However, it should be noted that the coefficiency of performance of heat pumps falls off at higher temperatures, affecting the real-world efficiency, and subsequently operating costs.
Bivalent approach
The low-carbon credentials of heat pumps are well established in new-build and some existing buildings, but capital expenditure and operating costs may influence the design strategy decision when dealing with older NHS buildings. While the NHS’s aim is to transition to zero carbon technologies, full decarbonisation could take some time to achieve. So, for practical reasons, a balance may need to be struck to meet the year-round requirements for reliable, efficient, sanitary hot water.
On projects where an all-electric solution is not considered suitable, a bivalent approach to hot water generation using two energy sources should not be overlooked as an important step on the Net Zero path. With refurbishment projects, for example, where the natural gas supply might be maintained, there is the opportunity to use ASHPs to preheat direct gas-fired water heaters (DGFWH). (see Figure 2).
Integrating ASHPs and DGFWHs in a bivalent system can provide a practical solution to the project limitations previously described, while meeting hot water demand more sustainably, and making significant progress towards decarbonisation. Further, many DGFWHs are compatible with the projected 20% hydrogen blend into the natural gas network, enhancing the sustainability of the installation. In time, the remaining gas use can be cut by using green hydrogen models. In this way this approach offers a practical opportunity for important immediate efficiency gains and emission reduction in older NHS buildings
Advantages from a design perspective
From a design perspective, there are advantages to be gained from using high-efficiency DGFWHs over indirect DHW systems (boiler calorifiers) and direct electric systems – storage, for one. DGFWHs have greatly reduced storage compared with other systems, which means less weight – and fewer issues if being sited within roof top plant rooms. Importantly, energy usage is also reduced, along with associated emissions, as there is less water to maintain at temperature.
Legionella is another case in point. Some DGFWHs come with in-built antiLegionella functions as standard, which make control of Legionella far more straightforward, reducing maintenance time for Estates and Facilities managers. Those DGFWHs with smart return temperature sensor technology have the ability to provide further energy and emission savings by reducing the time required to complete the pasteurisation process. As a final point, it is generally accepted that where a design includes renewable technology, such as heat pumps, project costs are higher.
Whether planning to install a complete plant room to serve a new-build hospital, or refurbish the hot water heating system in an existing building, it’s worth exploring the use of offsite solutions. Prefabrication makes everything easier – installation is faster and simpler, onsite time and labour are reduced, health and safety are improved, and quality assurance is enhanced.
How can the offsite technique be applied for DHW solutions? The options range from the largest containerised plant rooms to prefabricated modules that are purpose-designed to provide a high-quality plug and play solution. For example, if planning on integrating ASHPs in the next phase of the refurbishment project, now is a good time to consider using a bespoke, offsite prefabricated interface unit between the heat pump and cylinder or DGFWH technologies. This could integrate a specially sized plate heat exchanger (PHE), pumps and control panel, all designed bespoke to meet the specific project requirements. Each prefabricated module is typically designed using BIM tools and 3D computer-aided design (CAD) modelling. This enables revisions to be made collectively, while supporting best practice design, installation, operation, and maintenance.
Quality-controlled factory environment
Once the design has been agreed, production takes place in a quality-controlled factory environment. Thanks to the use of specialist machinery, improved control procedures, and comprehensive end-of-line testing, the highest build quality can be achieved with offsite solutions. An additional benefit is that offsite fabrication has the potential to reduce waste, leading to a lower environmental impact. When production is complete, the compact, wheeled interface unit is delivered to site for rapid connection, saving time, hassle, and space.
Point-of-use electric water heaters
A further opportunity to reduce emissions from hot water in hospitals and GP surgeries is to use point-of-use water heaters to provide safe hot water. Point-of-use electric water heaters can provide an efficient option in areas like washrooms or kitchens, as they only use energy when hot water is required. Installing a point-of-use water heater that incorporates anti-Legionella functionality, water pasteurisation, and anti-tamper design, will ensure that water is adequately stored, cycled, and distributed.
As hygiene-critical environments, it is vital that hospitals prevent bacterial build-up and cross-contamination. The UK Health Security Agency (UKHSA) recently highlighted the work that it is doing to help hospitals prevent the spread of infections.9 Working with hospitals and academic partners, UKHSA is attempting to gain a better understanding of how infections spread in different environments, which is key to reducing their spread, preventing outbreaks, and keeping the public safe Technology is already available to help deal with this. Good hot water heaters, for example, will now incorporate antibacterial silver ion agents to prevent the growth of bacteria. Silver ions work by puncturing holes in bacterial membranes, and binding to essential cell components like DNA, which prevents basic reproductive functions from occurring. However, it should be noted that concentration of silver should not exceed the recommendations set out in HTM 04-01 guidance
Combining this technology with pasteurisation will inhibit cultures from developing. Clinically-focused equipment should also have anti-corrosion fonts to prevent contamination from chemical breakdown of metal parts. This helps keep the surfaces clean and hygienic, and reduces the risk of cross-contamination.
Water quality
Implementing a robust water treatment strategy should be a key part of the maintenance programme to ensure efficient operation of equipment, and help extend the lifetime of products. Water quality can differ across the UK. Selecting products with polycarbonate tanks, for example, will limit the amount of scale that builds up in a unit, while suitable water treatment will raise the quality of water supplied in a hospital. This is especially important for the majority of south, east, and central England, where water is hard to very hard. Water treatment is also identified as another effective method of bacteria control. This is a specialism in its own right, and we would advise consulting with specialist water treatment companies.
Maintenance
Treating water is only one part of the process. Ongoing maintenance of the hot water system is also crucial to ensure that all the above criteria are continuously met. As prolonged disruption to a hospital’s water supply must be avoided, another consideration should be to install products that are designed for easy maintenance. Examples include equipment with built-in inspection hatches, multiple immersion elements, or multiple gas engine modules, that keep maintenance times to a minimum, and can offer inbuilt redundancy. This will free up time and stop unnecessary expense. Choosing robust products that are designed for easy upkeep and built to last will also help avoid unnecessary time and expense related to maintenance.
Technical guidance is available to support NHS Estates and Facilities managers in creating sustainable, energyefficient buildings that meet the needs of patients now and in the future. These documents include: Delivering a Net Zero Health Service, 1 HTM 04-01,8 and the NHS Net Zero Building Standard. 10
Plotting pathways
In conclusion, when it comes to hot water, there are challenges and opportunities associated with improving energy efficiency in hospital and healthcare buildings. Improving the energy efficiency of the hot water system will reduce energy demand and associated emissions and costs, while improving their operational performance for better outcomes for patients and staff. Quick wins to reduce energy demand, such as pipework lagging, should be acted on now. Upgrading any inefficient equipment with more energy-efficient technology might be an appropriate early stage in the decarbonisation journey. Using renewable and low-to-zero carbon technologies will further support the NHS in reducing its carbon footprint, but will likely require thorough planning
As each project and building type will have its own particular requirements, Estates and Facilities managers will benefit from advice and support to enable them to plan their own unique roadmap to the energy transition. The route they chose will depend on many factors, including costs, available space and electrical power, and reliability
Consult with specialists
A number of guidance documents are available, but due to the complexity of the challenge, it’s advisable to consult with specialists. Your manufacturer of choice should be willing to make available their experience and expertise, not just on their specific products, but also with regard to the legislation and guidance around this subject. As hot water experts, they should have an understanding of the unique requirements of each project, and, with an encyclopaedic knowledge of the latest technologies and techniques, be able to recommend the most appropriate solution. If the NHS is to make progress towards its Net Zero goals, the time for action is now. Plotting an achievable pathway is the first critical step
To discuss the topics raised in this article, email the author, Paul Marsden, at paul.marsden@baxi.co.uk
Paul Marsden
Paul Marsden is Specification manager at Baxi, a role he has held for 13 years. His entire career has been centred around commercial hot water generation and public health engineering. He uses his wealth of experience and expertise of hot water systems and renewable/ LZC technologies to help public health and mechanical engineers understand the relationship between the product/s, the application/s, and the system/s, they are designing. He has an ONC in Gas Utilisation, and City and Guilds in Gas Services, and has delivered a variety of training and CPD presentations and seminars.
More recently, he has developed training events and courses targeted at young and graduate engineers. An Affiliate member of both CIBSE and SoPHE, as well as a member of CIPHE, he is currently Chair of the SoPHE Industry Working Group.
References
1 Delivering a ‘Net Zero’ National Health Service. NHS England, October 2020. https://tinyurl.com/2p9xd32t
2 AR6 Synthesis Report: Climate Change 2023, IPCC, 20 March 2023. https://www. ipcc.ch/report/ar6/syr/resources/spmheadline-statements/
3 Press release: Climate change has arrived, yet the country is still strikingly unprepared. Climate Change Committee, 29 March 2023. https://tinyurl.com/ cj5n5fx9
4 Health and Care Act 2022. HM Government, 28 April 2022. https:// www.legislation.gov.uk/ukpga/2022/31/ contents/enacted
5 Press release: More support needed to help the NHS reach net zero. British Medical Association, 16 January 2023. https://tinyurl.com/wvxhzf3x
6 Heatwaves in 2019 led to almost 900 extra deaths in England. The Guardian, 7 January 2020. https://tinyurl. com/576txtzj
7 HSG274 Part 2. Legionnaires’ disease. The control of Legionella bacteria in hot and cold water systems. Health and Safety Executive, 2014. https://www.hse.gov.uk/ legionnaires/hot-and-cold.htm
8 HTM 04-01. Safe water in healthcare premises. Department of Health & Social Care, 21 May 2021. https://tinyurl.com/ mrxumuht
9 Using science to design out healthcare associated infections. UK Health Security Agency blog. 15 March 2023. https:// tinyurl.com/wm8vdbw7
10 NHS Net Zero Building Standard. NHS England. 22 February 2023. https:// tinyurl.com/3p2w8jf2