As the UK continues to decarbonise its building stock, the methods of delivering heating and hot water are changing. One such innovation growing in popularity is district heating, says Alexandra Leedham, Technical Team Leader of Renewable Energy at REHAU.

Supplied from a centralised heat source through a network of pre-insulated pipework, district heating delivers hot water to multiple properties without the need for individual heat sources. For facilities managers, this means time and money spent on maintenance is reduced to one heat source, while carbon emissions across multiple buildings are reduced.

Since the Government announced its ‘Net Zero’ 2050 targets, there is more pressure than ever on building services professionals to provide low carbon heat and hot water in buildings. Couple this with increasing demand to improve efficiency and lower the cost of energy bills, the latest district heating innovations must be able to deliver lower emissions, great heating efficiency and low heat losses across the network.

Fourth generation heating At present, most European district heat networks are part of the third generation, with water circulating at 70-95°C. However, there is a growing trend towards new fourth generation systems, with flow temperatures of 50-60°C. Because of this generation’s comparatively low-temperature design, heat loss or wastage within the network is reduced, meaning additional cost savings can be realised. Furthermore, this new generation of systems retains the traditional advantages associated with centralised district heating networks, including less time and money spent maintaining individual boilers, and, crucially, reducing carbon emissions.

This generation has also been designed with a focus on low carbon heating sources, as the lower flow temperatures are ideally suited to centralised heat pumps or waste heat sources. Such heat sources can be introduced to a network after initial installation, meaning upkeep and maintenance is as simple as the initial installation.

For new commercial facilities, the launch of the Green Heat Networks Scheme, which replaces the Heat Networks Investment Project (HNIP) from 2022, favours this low carbon solution as a sustainable option going forward. As with the HNIP, this scheme will award grants to projects both domestic and commercial that implement sustainable, low carbon district heating systems – a key consideration for facilities managers involved in the planning of new premises in the future.

In addition, regulations and standards are also starting to favour district heating. The latest version of the Standard Assessment Procedure for building regulations (SAP 10.1) sets standards for a new lower emissions factor for electricity, which advocates heat pumps as a ‘greener’ solution. Compared to the SAP 2012 metric of 0.519 kgCO2

44 | TOMORROW’S FM kWH, SAP 10.1 proposes a value of 0.136 kgCO2 /kWH – a

75% improvement in heat pump derived electricity carbon savings from previous figures.

As grants and legislation continue to be implemented, low carbon and energy efficient heat pumps are proving to be a viable alternative to traditional systems during this process of grid decarbonisation. It is therefore important for facilities managers to understand which innovations are best suited to low-carbon networks, particularly when it comes to material choice.

Low-carbon with polymer Where previously steel has been the main material for use in district heating applications, networks using all-polymer pipework are becoming increasingly commonplace. Using reinforced polypropylene (PP-R) pipe as a main spine, the network can carry higher heat loads and supply more buildings. From this spine, the easy connection to flexible PEXa pre-insulated secondary spines and user connections reduces installation costs as the network is extended.

As fourth generation technology moves to the forefront, polymer district heating networks are also well suited to the lower flow temperatures, achieving lower heat losses across the network and an expected lifespan of over 50 years. With sustainability a key factor for many industries, polymer systems can allow facilities managers to futureproof their means of delivering heating and hot water for years to come.

“There is a growing trend towards

new fourth generation systems, with flow temperatures of 50-60°C.”


By implementing a PP-R pipe as a main spine, facilities managers could also see 19% less pressure loss across their network compared to steel. System failure risk or costly repairs that can occur through corrosion or clogging from corrosion build up in traditional steel systems are therefore markedly reduced, while lower pumping costs are achieved to further drive down cost. Additionally, PP-R also follows the trend of more sustainable heating, with the piping being 100% recyclable. As PP-R is 37% lighter than steel, less emission-inducing freight miles are required to transport it to the installation site.

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