Safe, efficient hot water in healthcare
Andy Green, Technical Director at Baxi Commercial Solutions, looks at the challenges and opportunities to drive down emissions associated with hot water generation for hospitals and healthcare premises while prioritising a safe and reliable supply
With healthcare buildings contributing 15% of the total NHS carbon footprint[1], reducing emissions in this sector is essential if the health service is to reach its world-first net zero goal.
The NHS has the ambition to be the first ever net-zero national health service and has formally adopted two targets, set as the earliest possible credible dates to achieve net zero emissions. The first, for the NHS Carbon Footprint (emissions under NHS direct control), 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, (which includes its wider supply chain), which sets a target for net zero by 2045, with an ambition for an interim 80% reduction by 2036-2039.
The high demand for hot water provision that is frequently associated with healthcare premises makes it a clear target for emissions reduction. But it’s one that comes with certain challenges for facilities and estates managers.
Hygiene-critical environments have a number of specific requirements. Ensuring an adequate, reliable hot water supply is key to creating comfortable conditions for patients and staff. Associated with this is the need to avoid the risk of scalding and burns, particularly for the protection of vulnerable patients.
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 60ºC and distributed so that it reaches 55ºC in healthcare premises to reduce the risk of legionella.[2] Temperature control will need to be provided at hot water outlets used by persons at risk of being scalded.
Ongoing maintenance of the hot water system is therefore vital to ensure that all the above criteria are continuously met.
The vast variety of buildings and heating systems within the NHS estate adds to the complexity of the challenge. In short, while there may be numerous options, not all will be suitable for each project. With this in mind, let’s explore some of the potential solutions to achieving more sustainable hot water generation in healthcare premises.
Electrification and heat pumps
The drive towards decarbonisation and electrification of heat (including hot water) means that the favoured approach today will likely be to install heat pumps.
There are two types of heat pumps. Some are able to deliver the high flow temperature required to meet the design hot water temperature. The benefit of using high temperature heat pumps is that it avoids the need for an alternative form of technology to store the domestic hot water (DHW) above legionella temperatures (60ºC or higher).
However, while this option offers greater design flexibility, it should be noted that the coefficiency of performance of heat pumps falls off at higher temperatures. Another solution, therefore, might be to use lower temperature air source heat pumps with direct-fired electric water heaters. This solution would involve much higher volumes of stored domestic hot water – certainly compared with high energy, low storage direct gas fired water heaters which the building may previously have relied on. Therefore, it’s important to consider potential issues relating to available space and weight for the larger cylinders – particularly when dealing with roof top or non-basement plant rooms. Controlling legionella within the larger volumes of stored water will also need to be managed.
Multivalent approach
While the low carbon credentials of heat pumps are well established, capital expenditure and operating costs may influence the design strategy decision. Given the year-round requirement for hot water in healthcare, a balancing act between carbon reduction and operating costs could be required.
On projects where an all-electric solution is not considered suitable, a multivalent approach to hot water generation should not be overlooked. With refurbishment, for example, where the natural gas supply might be maintained, there is the opportunity to use air source heat pumps to preheat direct gas-fired water heaters (DGFWH).
There are many advantages of using high efficiency DGFWH – especially those like the Andrews MAXXflo EVO and SUPAflo EVO which come with anti-legionella functions as standard – over indirect DHW systems (boiler calorifiers) and also often compared to direct electric systems. DGFWHs have considerably reduced storage compared with other systems, meaning less weight and fewer issues with roof top plant rooms. Control of legionella is more straightforward and recovery times reduced. It is also generally accepted that where a design includes renewable technology, such as heat pumps, solar PV or CHP for example, project costs are higher.
Water treatment
Implementing a robust water treatment strategy should also be a key part of the maintenance programme to ensure the efficient operation of equipment and 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 a conditioner 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. For an entire overview of legionella control, refer to HTM 04-01, part B,4.
This is a specialism in its own right, and we would advise consulting with specialist water treatment companies.
Industry support
Transitioning huge hospital premises from gas-powered steam or high temperature water heating systems to a low-carbon solution can be a hugely complex and daunting task for estates managers for the reasons outlined above.
As each project and building type will have its own particular challenges, estates and facilities managers will look to the building services industry for advice and support to enable them to plan their own roadmap to the energy transition. The route they chose will depend on many factors, including costs, space requirements, available electrical power and reliability.
Your manufacturer of choice should be able to offer the variety of equipment and solutions required to meet all individual project requirements. They should also be able to provide guidance as to the most suitable technologies to use and how they will integrate with the building design as a whole. Accurate sizing is one example, to ensure sufficient DHW without oversizing the system and wasting precious energy. Look for manufacturers who offer electronic sizing tools, like Andrews’s Size-it, that make it easier to manage, match and measure up the different parts of the building type and hot water requirements.
At Baxi we have decades of experience through our technical sales teams of working with consultants and contractors to identify the various options and the most appropriate solutions. Where expert help is required, we can work together as an industry to help hospitals plan and achieve their net-zero pathway while avoiding the risks associated with hot water provision.
Infection prevention with POU water heaters and boiling water units
A further consideration in hospitals and healthcare premises is the inclusion of point-of-use water heaters, which could be fed by solar PV, for the immediate production of safe hot water.
Installing a point-of-use water heater that incorporates anti-legionella functionality will ensure that water is adequately stored, cycled and distributed.
An added concern in hygiene-critical environments is the need to prevent bacterial build up and cross-contamination. One solution might be to use electrically powered boiling water units like Heatrae Sadia’s Supreme that incorporate Polygiene Biomaster®, an antibacterial silver ion agent, to prevent the growth of bacteria. This helps keep the surfaces clean and hygienic and reduces the risk of cross-contamination, aiding HTM 04-01 compliance.
Choosing robust products that are designed for easy upkeep and built to last will also help avoid unnecessary time and expense related to maintenance.
Sources
1 www.england.nhs.uk/greenernhs/2022/10/blog-drive-for-energy-efficient-healthcare-is-delivering-for-patients-and-planet/
2 www.hse.gov.uk/legionnaires/hot-and-cold.htm
