Heat networks and ambient loops (5th generation district heating)
How ambient-loop (fifth-generation) heat networks work, how they differ from a central heat pump, what funding status looks like and who they are really for.
What an ambient loop is
A traditional district heating network sends hot water, often at high temperature, from a central boiler or energy centre to the buildings it serves. An ambient loop, sometimes called a fifth-generation or 5GDHC network, works differently. A pipe circuit carries water at a low temperature close to the surroundings. Each connected building has its own heat pump, which takes heat from the loop and raises it to the temperature that building needs. A building that needs cooling can do the reverse, putting heat back into the loop.
The loop is also a place to share heat between buildings. If an office is rejecting heat while a nearby block needs it, the loop can pass heat from one to the other, and a ground-source borehole field, a river or waste-heat source can top up whatever the buildings do not balance between themselves. Because the loop runs near ambient temperature, heat losses from the pipework are small and the pipe can be uninsulated plastic in some designs. That is a general description; the actual design depends on the site, and ground-source engineering is covered in the ground-source guide.
Central heat pump or per-building heat pumps
The key design decision is where the heat pumps sit.
| Question | Central energy centre | Ambient loop with per-building heat pumps |
|---|---|---|
| Network temperature | Hotter, so more pipe insulation and heat loss | Near ambient, so little heat loss |
| Where the heat pumps are | In one plant room, operated as one asset | In each building, each with its own electricity connection |
| Metering and billing | Heat is metered and sold to each user | Each building pays for its own electricity; the loop operator charges for loop use |
| Existing buildings | Easier to connect where radiators are already at high temperature | Needs each building to be able to run on a heat pump |
| Cooling | Not built in | Can be built in by design |
Neither is better in every case. A central plant concentrates operation and maintenance in one place and can connect older buildings with high-temperature systems. A loop spreads electrical load across several connections and suits new buildings with low-temperature heating. Some schemes combine both. A network of either type may need a distribution network operator to reinforce the local electricity supply, and that is a question for the early design stage.
Whether your building could one day sit inside a designated zone is a separate question from whether an ambient loop suits it; the heat network zoning guide sets out what has been decided in England and what is still proposed.
Funding: the Green Heat Network Fund
The Green Heat Network Fund (GHNF) is government funding for heat networks, as opposed to heating in individual buildings. According to its GOV.UK page it is open to public, private and third-sector organisations in England and Wales, sole traders cannot apply, and funding is drawn down to 2029-30. It is delivered by Triple Point Heat Networks Investment Management. The page showed Round 12 open until 11.59pm on Friday 25 September 2026, so that round has now closed, and it listed no later round. Check GOV.UK for the next round before you plan around it.
The Public Sector Decarbonisation Scheme, which funded some council and public building heat projects, has closed; Phase 4 closed in November 2024 and was the final phase. Individual buildings that need 45 kW thermal or less for a single heat pump (70 kW thermal for a multi-unit system) can look at the Boiler Upgrade Scheme instead; see grants and funding.
Heat network zoning
The Energy Act 2023 created the legal framework for heat network zoning in England. In general terms, zoning means identifying areas where a heat network is likely to be the lowest-cost way to decarbonise heat, and using the powers that follow to require certain buildings in those areas to connect or to consider connecting. Local authorities are expected to take a central role in identifying zones. The details, timings and exemptions are set out in legislation and guidance that this guide does not summarise; read the current position on GOV.UK and talk to your local authority if a scheme is proposed near your site. If you are a building owner in a proposed zone, the practical question is whether to connect to a network or to install your own heat pump.
Who this is for, and the scale limits
Heat networks and ambient loops serve groups of buildings. They fit:
- Developers of mixed-use or multi-building sites, where the network can be designed in from the start.
- Campuses such as universities, hospitals and business parks with one owner or a close group of owners and heat demand across several buildings.
- Councils and housing providers with a cluster of public buildings and an interest in zoning.
The honest limits are real. Pipework, boreholes or energy centres, metering, billing, governance and a long-term operator all add cost and complexity, and the buildings must be close enough to share infrastructure. A single shop, small office or factory unit has no use for a network and is better served by its own air-source heat pump or a costed alternative. Even for suitable groups, feasibility work by independent engineers and legal and funding advisers comes before any commitment; this guide is a starting map, not a design.