First step of the low-carbon water-source heat network at Welborne Garden Village delivered
July 30, 2025
Rendesco have delivered the design and build for the first ambient heat network of its kind utilising water from an operational reservoir owned by Portsmouth Water. The system will be owned and operated by joint venture partner, Last Mile.
The first of 700 homes are already receiving low-carbon heat, cooling and hot water.
80% lower emissions than traditional gas heating and 50% less CO2 than air source heat pump alternatives
The first phase of the multi-stage project, led by Buckland Development, will include the construction of up to 700 homes. A primary school and a village centre featuring shops, pubs, and cafés, all connected to an ambient heat network, will follow. This network is designed to produce 50% less CO₂ emissions compared to a typical air source heat pump system.
The heat network uses a unique, first-of-its-kind approach in the UK, installed by Rendesco. It draws stable temperature water from the Portsmouth Water’s nearby underground Hoads Hill Reservoir and feeds into an energy centre where a heat exchanger transfers energy from the water into an ambient heat network. Individual heat pumps at each property then convert that energy into space heating and hot water. The heat network serving the properties is a closed loop system, separate from the water network that circulates water from the reservoir to the energy centre. This ensures there is no risk to drinking water quality and supply.
Read also: The benefits of geothermal heat networks
It can also use the reservoir as a heat sink for cooling in warmer months and facilitates building-to-building heat transfer, transforming excess heat produced by cooling in one building into heat and hot water for another building. As a result, the complete network is significantly more efficient than alternative heat solutions, resulting in the potential to save over 272,000 tonnes of carbon in the first 25 years of operation.
As Welborne’s master developer, Buckland has assembled a consortium committed to innovative technologies that encourage low carbon living in connected and energy efficient homes, integrated with extensive publicly accessible green space.
Read also: Future Homes Standard passes another major milestone
The Future Homes Standard is anticipated to require developers to reduce emissions for new homes by 75-80% compared to current standards. While many are focused on meeting this goal, few are comfortable with managing utilities once their developments are completed as this is not their traditional business model. Rendesco has worked to design and build the heat network for Last Mile and will be owned and operated by their joint venture, Last Mile Heat.
Tom Page, Managing Director for Design and Build, Rendesco, commented:
‘In partnership with Last Mile, Rendesco have designed and are currently onsite building one of the world’s largest ambient networks; the first heating and cooling ambient network in the world to use a water reservoir as the heat source/heat sink.
Welborne Garden Village is a unique and innovative sustainable community with low carbon emissions and low energy costs for residents. Our ambient network provides all heating, cooling and hot water to residents and is the cheapest form of low carbon heating and cooling available.
At Rendesco we are proud of the difference our contribution is making toward the shaping of future, low-carbon communities such as Welborne.’
Rendesco are proud to have designed and built the heat network, achieving net-zero, low emission targets beyond the Future Homes Standard. Via a dedicated onsite and in-office team to support the installation of the heat network, sustainable and reliable heating will be delivered to hundreds of new homes.
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