Trelissick House, Cornwall ground source heat pumps energy

Trelissick, an 18th-century mansion with sprawling gardens in Feock, near Truro, upgraded its old-fashioned oil boilers to more efficient, ground source heat pumps last autumn. Ever since, the 165kW system has heated the draughty Grade II* listed building, as well as the estate’s bookshop and cafe.

A ground source heat pump system provides all of the estate_s heat (Image: Supplied)

The National Trust used a mix of grants and government funding for the retrofit, taking the charity one step closer to its goal of becoming carbon net zero by 2030.

The system was designed by Chacewater-based company, Kensa Heat Pumps. Kensa is one of the leading manufacturers of heat pumps in the South West, installing more than half of the UK’s ground source heat pumps each year.

Trelissick became a National Trust property in 1955 (Image: Supplied)

The 165kW ground source heat pump system harnesses natural heat from underground – saving the property tonnes of carbon a year.

In conjunction with last month's Great Big Green Week – a nationwide celebration of action on climate change – visitors were able to tour Trelissick’s basement, where the heat pump system is housed.

A Trelissick tour guide explained: “The reason it requires so much power is that the house itself has got to be kept at a certain temperature to preserve the fabric of the house. There is no double glazing, no central insulation in the walls, doors, windows, roof, any heat really goes straight out.”

After the retrofit, Trelissick’s carbon footprint was reduced by 64 tonnes, while bills have stayed relatively stable in a volatile energy market.

Improving the energy efficiency of historical properties – those built before 1919 – could reduce carbon emissions from the UK’s buildings by 5% each year, according to a recent report from the National Trust, Historic England and leading property organisations. Retrofitting the UK’s old buildings could also generate an extra £35bn in new money, the report adds.

Dan Roberts, Technical Director at Kensa Heat Pumps, said: "Installing ground source heat pumps in Trelissick, a Grade II* listed 18th-century mansion and parkland is a fantastic example of how historic buildings can benefit from low carbon heating.

"The property was retrofitted with a 165kW ground source heat pump system to replace the old oil boilers, providing the property with 100% of its heating and hot water year-round and reducing the estate's carbon emissions by around 64 tonnes a year.

Trelissick opened up its basement in celebration of Big Green Week (Image: Supplied)

"Now the installation has taken place, there is very little to see as all the infrastructure is underground so the outside of the property itself is completely unaffected.

"It was a privilege for Kensa to assist the property in their reduction of carbon emissions and switch to a more energy-efficient system in a historically important building only five miles from our factory and help work towards the National Trusts' commitment to be a Net Zero organisation by 2030."

Gareth Lay, General Manager for National Trust Heart of Cornwall portfolio, said: “This was a fantastic project that has allowed Trelissick to move away from its reliance on fossil fuels for heating and takes us in the right direction to reach our organisational strategic aim of becoming net zero carbon by 2030”.