Decarbonisation of the UK’s building stock is a priority that has taken centre stage in

discussions around suitability. Given its effect on choice of heating solutions, low carbon solutions like district heating are becoming a more attractive proposition. Alexandra Leedham, technical leader – Renewable Energy at REHAU, explores the latest developments


istrict heating networks supply heating and hot water to numerous properties via

an underground pre-insulated pipe network, eliminating the need for individual heat sources. It is becoming a popular solution among developers and operators, as much of the maintenance is centralised to a single energy centre. Similarly, it allows emissions reductions in line with sustainability-minded legislation – most prominently, the Government’s target to reduce carbon emissions to ‘net zero’ by 2050. These targets, along with the latest 10-point

Plan for a Green Industrial Revolution, have made sourcing low-carbon heating and hot water systems a priority for building professionals. This, combined with continued onus on lowering energy bills and driving up efficiencies, means that district heating systems could be the key to lowering emissions and improving heating efficiency.

EVOLVING HEAT NETWORKS Most heat networks across the UK and Europe are classed as third-generation, with water circulating at 70-95˚C. However, more fourth-generation systems with a comparatively lower 50-60˚C flow temperature are being implemented, due to less heat loss across the network making them more efficient and cost-effective. Alongside these benefits, fourth-generation

systems, due to their centralised design, reap the same benefits as their predecessors. For building services professionals, this includes reduced carbon emissions and easier, more cost-effective, maintenance due to eliminating individual boilers. Fourth-generation systems were also

developed with low-carbon heating sources in mind, with lower flow temperatures suiting centralised heat pumps and waste heat sources, leaving them well-placed to help contribute to net zero goals. With district heating, heat sources can be changed or added over time, increasingly the flexibility for the heat network operator.

HELPING LEGISLATION The Government’s 10-point plan has signalled the beginning of low-carbon heating development and, as such, there will be pressure

on building services professionals to fulfil this. Funding initiatives such as the Green Heat Networks Scheme (GHNS) will help in this transition, and favour these low-carbon schemes in both residential and commercial applications. Due for launch in 2022, the GHNS will replace the existing Heat Networks Investment Project, and will similarly award grants to domestic and commercial projects implementing sustainable, low-carbon district heating systems. Shifting standards and regulations are also

creating an environment more amenable to district heating systems. For instance, the latest Standard Assessment Procedure for building regulations (SAP 10.1) consultation sets standards for a new lower emissions factor for electricity, which advocates heat pumps as a more sustainable solution. Compared to the SAP 2012 metric of 0.519 kgCO2 proposes a value of 0.136 kgCO2

/kWH, SAP 10.1 /kWH – a 75%

improvement in heat pump derived electricity carbon savings from previous figures. Green progress and carbon-neutral

legislation will continue to promote low- carbon, heat pumps and waste heat compared with traditional fossil fuel systems. As such, building professionals must understand what innovations best combine with low-carbon networks, and the impact of material choice has on the resulting solution.

AN ALTERNATIVE TO STEEL Traditionally, steel has been the material of choice for district heating systems, however, recently polymer networks are growing in prominence. With reinforced polypropylene (PP-R) pipe now available as the main spine, polymer networks are now able to provide heat


loads up to 16MW. Flexible PE-Xa pre- insulated pipework in coils can then be easily connected to this main spine, ensuring more cost-effective installation for heat network developers as they extend networks. The growth of fourth-generation district

heating technology has further increased the implementation of all-polymer networks, as lower flow temperatures allow for less heat losses. Taking into account the material’s expected 50-plus year lifespan, polymer systems are being considered a sustainable means of futureproofing a building’s heating and hot water requirements.

By implementing a PP-R pipe main spine,

building and energy managers can provide properties with reduced pressure losses of up to 19% when compared to a steel solution. Minimised corrosion risks also minimise possibility of system failure risk and expensive repairs thereafter, with costs further reduced due to lower pumping costs. As PP-R is up to 37% lighter than steel, it is not only easier to handle on site, but also lowers emissions during transportation. This sustainability is improved further by the fact that the PP-R material is 100 per cent recyclable. While pressure on building services

professionals to decarbonise their operations and select low-carbon solutions grows, considerations around reducing materials used and installation times continue to endure. Because they eliminate expansion bends present in steel networks, polymer pipework helps reduce installation times, with less materials and welding also required across the scheme. PP-R pipe’s lighter weight and the PE-Xa pipe’s flexibility also allows contractors a quicker and more flexible installation. The increasing need to decarbonise heating

and hot solutions, combined with traditional challenges around quicker, more cost-effective installations without compromising quality, means building professionals are under more pressure than ever before. Polymer district heating systems, specifically of the fourth generation, provides a practical, low-cost option for these amenities, delivering easy installation and maintenance.



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