Welborne Garden Village – Multi-award-winning reservoir sourced ambient heat network

Welborne Garden Village is set to be one of the UK’s largest private mixed-use developments, delivering 6,000 homes, commercial premises and community buildings – including schools and healthcare facilities – within 180 hectares of green space. When complete, the developer, Buckland Development, will have created a newgeneration sustainable village that significantly reduces emissions while meeting growing housing demand.

Meeting the Future Homes Standard without operational burden

The development required a Future Homes Standard compliant heating solution in the form of an ambient heat network: the lowest-carbon form of heating, reducing emissions by 80% compared to gas. However, these networks have a higher CapEx and many developers lack the appetite or in-house expertise to manage them long term. Success would therefore require commercial and technical innovation.

Capitalising on unique local geography

The underground Hoads Hill Reservoir nearby enabled a first-of-its-kind heat network, harnessing ambient heat from the water mass. However, this complex feat required innovative engineering and extensive coordination with Portsmouth Water.

First-of-its-kind water-source heat network

Last Mile partnered with Rendesco to design and build the heat network, which extracts heat energy from the reservoir and transfers it to a decentralised ambient system where individual heat pumps provide heating and hot water to each home. The closed loop uses a tiny fraction of the reservoir’s capacity without impacting the water supply. In warmer months, the system can use the reservoir as a heat sink for cooling. It also facilitates building-to-building heat transfer – waste heat from cooling one building heats others – creating a more efficient and resilient solution adaptable to future climate conditions.

Integrated multi-utility provision

Last Mile was also appointed as the water and sewerage provider for Welborne under a New Appointments and Variations (NAV) licence. The scope of these works included the design, inspection and technical approval of:

• Water distribution networks and a pumping station
• Foul and rainwater sewerage
• Sustainable drainage systems, including surface water networks, basins and ponds, filter strips and soakaways

Full lifecycle approach removes developer burden

Last Mile’s unique offer includes adopting and operating networks on behalf of developers. Once the first phase was completed, Last Mile adopted the heat, water, wastewater and SuDS networks. An up-front asset valuation payment, seamless adoption, and efficient ongoing management reduced the CapEx and eliminated operational costs for Buckland Development.