18kW Vaillant Heat Pump Installation, 1910 Farmhouse Retrofit in Sussex
This project was one of last year’s standout installations. A 1910-built farmhouse with separate stables, requiring a properly engineered renewable heating solution capable of delivering comfort across multiple buildings, without compromise.
The Challenge
Older rural properties present unique challenges. This farmhouse, built in 1910, had the thermal characteristics you’d expect from a property of that era, solid construction, varied heat loss across different areas, and a requirement to heat both the main residence and the stables.
The brief was clear:
Deliver consistent, reliable heating throughout
Maintain strong hot water performance
Ensure high seasonal efficiency across both buildings
Future-proof the property with a long-term low-carbon solution
This wasn’t a simple boiler swap. It required proper design, correct emitter sizing, and careful commissioning.
Our Solution
We installed 2x Vaillant air source heat pump with a combined output of 18kW, positioned externally with careful consideration for airflow, service access, and system performance.
The system was designed to independently serve:
The main farmhouse heating circuit from the larger 12kW unit
The stables heating circuit from the smaller 5kW unit
Domestic hot water via a Heat Geek specified cylinder heated by the 12kW unit
Separate performance targets were achieved across each area to reflect their different heat demands. The stables area was better insulated and fitted with UFH which meant that the flow temperature requirement was much lower than the main house. This made the independent installation of 2x heat pumps rather than a cascade linked together the best option, maximising the efficiency of the system.
The hot water system was paired with a high-performance Heat Geek cylinder, designed to maximise coil transfer efficiency and optimise heat pump performance.
Performance Results
The commissioned system delivered impressive seasonal results:
Farmhouse heating SCOP: 4.0
Stables heating SCOP: 3.9
Domestic hot water SCOP: 3.5
For a property of this age and scale, these figures demonstrate the benefit of correct design and commissioning.
Comfort levels throughout the house are stable and consistent, with low flow temperatures delivering steady background warmth rather than high spikes of heat. The stables benefit from controlled, efficient heating without excessive running costs.
Why It Matters
Installing a heat pump into a 1910 farmhouse isn’t about chasing headline efficiency figures, it’s about delivering real-world performance in challenging buildings.
This project shows that with:
Accurate heat loss calculations
Proper system design
Correct cylinder selection
Careful commissioning
Even older rural properties can achieve excellent seasonal performance and dependable comfort.
At Option Energy Solutions, this is the standard we aim for, well-designed, properly commissioned renewable heating that works as intended, year after year.
Installed by Option Energy Solutions, Heat Geek Elite Partner for Sussex region 
Call 01903 814777
💻 Learn more: optionenergysolutions.co.uk/heat-pumps
