The UK Net Zero Carbon Buildings Standard Guide: Part 8: District heating and cooling networks

This section outlines the requirements for buildings connected to district heating or cooling networks under the UK Net Zero Carbon Buildings Standard. This part of the standard aims to ensure that district heating and cooling networks contribute to net zero carbon buildings by reducing reliance on fossil fuels and improving energy efficiency.

Key Points

• Scope: All building types connected to a district heating or cooling network must assess and report operational energy use, carbon emissions, and the carbon content of heat/coolth supplied by the district heating network
• Metrics: Carbon content (kgCO₂e/kWh) of the heating/cooling network is a pass/fail metric, while energy use (kWh/m²/yr) and carbon emissions (kgCO₂e/kWh) of the building associated with heat/coolth supplied are reporting metrics.
• Measurement: Heat/coolth supply must be measured with heat meters. Carbon emissions factors specific to the heating or cooling network must be calculated. Emissions factors for fuels used must be the conversion factors published by UK Government at the time of the assessment. 
• Recovered Heat/Cooling: Recovered heat or cooling is attributed zero emissions, but energy associated with extraction and distribution is included.
• Submission Requirements: Verifiers require operational energy data, carbon emission factor calculations, details on the district network, and decarbonization plans for fossil fuel-based networks.
• Limits and Pass/Fail Criteria: 
  • Existing Networks: Must have a plan to transition to non-fossil fuel heat/coolth by 2040 and meet specific carbon content limits. 
    • The carbon content limit for heat is equivalent to a heat network with an air source heat pump with a seasonal efficiency (SCOP) of 2.8, and network losses of 20% and parasitic energy use of 2%.
    • The carbon content limit for coolth is equivalent to an on-site chiller with seasonal efficiency (SEER) of 3.0.
  • New Networks: Must not use fossil fuels and meet stricter carbon content limits. 
    • The carbon content limit for heat is equivalent to using an on-site air source heat pump with a seasonal efficiency (SCOP) of 2.8, with zero losses and parasitic energy use. Meaning in reality it would be equivalent to a system with a higher SCOP to account for losses which are inevitable.
    • The carbon content limit for coolth is unchanged from the existing network limits and equivalent to an on-site chiller with seasonal efficiency (SEER) of 3.0.

It’s good to see that the targets for heat networks in particular are ambitious. Based on current technology and network design standards it is unlikely new networks will meet the requirements without being connected to waste energy sources. In addition, the availability of eligible heat networks locally available to the building may deem it impossible for the building to meet the requirements of the standard, particularly considering the connection to heat networks often prioritised by planners.

Aspects we think work well

• The standard sets ambitious targets for new and existing heat networks which the building is connected to
• Networks which recover heat/coolth are incentivised
• It is based on measured data, and encourages monitoring of energy use and carbon emissions associated with district heating and cooling networks
• The assessment is based on carbon conversion factors which are current at the time of the assessment.

Aspects recommended be considered for further development

• Planning requirements generally prioritise the connection to heat networks, in particular in heat network priority areas, but there is a good chance that the locally available heat networks (whether existing or new) will not meet the standard’s targets. This could mean there is no way for the building to achieve these requirements for net zero
• Reporting against kWh/m²/yr favours larger lower density housing, while higher density affordable housing will generally perform less well against this metric
• While recovered heat/coolth is attributed zero emissions, should consideration of the environmental impact of the source of the heat be considered (e.g energy from waste incinerators)
• District heat networks often use gas boilers to meet peak loads during very cold spells, which contribute to a very small portion of the annual heat supply and carbon emissions. This can significantly reduce the required amount of low carbon technology required, making the district heat network financially feasible. This standard will not accept new networks adopting this approach as eligible. An alternative is electric boilers, however this may not be feasible in some areas due to constraints on the local electricity grid. 
• The definition of an existing network could be clearer.

Dagenham Green

Max Fordham provided the design of a large energy centre serving 4000 dwellings in Dagenham Green. The network is fossil fuel free, with the vast majority of heat delivered with air source heat pumps, with back-up electric boilers meeting the infrequently expected peak loads. Max Fordham also provided the design for the site wide heat network, designed to meet or exceed CP1 best practices.

Church Street is a net zero carbon regeneration scheme comprising approximately 1200 homes over three adjacent sites. The Max Fordham design comprises an ambient loop heat network providing heating and cooling, with 100% of the heat supplied by energy-efficient heat pumps. The whole project was designed to robust passive house principles.