Case Study

isoenergy’s largest heat pump installation at National Trust

A National Trust property is poised to achieve an annual saving of 30,000 litres of oil by transitioning to a groundbreaking ground source heat pump with specialists isoenergy.

Kingston Lacy at the National Trust is making strides in sustainability with a groundbreaking ground source heat pump, set to save 30,000 litres of oil annually. This marks a departure from traditional heating methods, ensuring a steady, gentle heat for the Dorset mansion and standing out as one of the Trust's largest heat pump projects.

Over time, Kingston Lacy, designed to emulate a Venetian palace nestled in the English countryside, has relied on open fires, coal, and oil boilers to maintain its warmth and dryness. 

In a groundbreaking move, a state-of-the-art ground source heat pump has been introduced to safeguard this magnificent Dorset country mansion and its impressive collection of artworks by renowned masters such as Velázquez, Titian, and Rubens. 

The innovative system is anticipated to contribute to the preservation of the art collection by delivering consistent, gentle heat without abrupt temperature fluctuations while achieving a significant annual saving of 30,000 litres of oil. This project stands out as one of the National Trust’s most extensive heat pump endeavours to date and marks the charity’s inaugural installation of a high-temperature ground source system. 

Ambient heat from the ground

The erstwhile oil tank has been replaced by an extensive network of almost 6,000 meters (19,685 feet) of underground pipes. These pipes harness natural ambient heat from the ground and channel it to four high-temperature heat pumps, warming both the 17th-century mansion and its adjacent courtyard buildings. 

The pipework installation involved drilling 32 vertical boreholes in an overflow car park, with each hole 180 metres deep. 

isoenergy is working with various partners on the project, including ADP Drilling, who are now on site and starting to sink the required boreholes in an overflow car park area.

After two years of meticulous work, specialists conducted thorough archaeological and ecological surveys to safeguard the historic parkland. This includes Iron Age hillforts, heathland, and water meadows. 

In addition to the environmental benefits, with an estimated annual carbon saving of approximately 57 tonnes, implementing the new heating system eliminates the risk of oil spills associated with the previous boilers and storage tanks. 

The trust also says the heat pump will improve the conservation of the building and its collection by stabilising the temperature and humidity levels. 

Energy innovations along the way

Owen Griffith, the National Trust’s lead renewable heat project manager, said: “Even in the most historically significant settings like Kingston Lacy, it’s possible to integrate these modern technologies. 

“Not only will the heat pump reduce the property’s dependency on fossil fuels, but it’ll create a safer environment and improve conditions for the collection items here. 

“Magnificent buildings like these have been around for centuries, but their heating systems have evolved – from open fires to coal boilers and then oil boilers, with many energy innovations along the way. This is simply the next step in Kingston Lacy’s history and preservation.” 

Griffith added: “What we’ve found when we’ve moved from fossil fuel conservation heating to heat pump conservation heating is that extending the heating time means that we have a longer duration of lower-grade heat coming into the building, so it’s a lot gentler. We’re able to stabilise the internal environment over a longer period so daytime/night-time fluctuations, for example, are balanced out. 

“You don’t get the spikes in heat from that you get from fossil fuels. It means we have a more stable environment that reduces the likelihood of mould growth and insect infestation.”