Kew's Temperate House now heated by heat pump energy centre funded through PSDS

The Temperate House at Kew Gardens is now heated by an air and water source heat pump system housed in a new energy centre, Salix Finance said after attending the ceremonial opening of the facility.

The energy centre occupies what was previously known as "stable yard boiler house 15" and supplies heat to the nearby glasshouse, according to Salix. Funding came through the Public Sector Decarbonisation Scheme (PSDS), which Salix delivers.

Alternative Heat, which acted as principal contractor and principal designer, said it had completed the decarbonisation of the Temperate House. It said the project was part-funded through the PSDS and also covered the neighbouring Evolution House.

Owain Davies, client relationship adviser at Salix, said: "It's incredibly rewarding to see the project at the transformed energy centre come to a conclusion and to have achieved such a notable milestone."

The building

Salix describes the Temperate House as a Grade 1 listed Victorian glasshouse and the largest surviving Victorian glasshouse in the world. The plants inside are tender species that need to be kept at a minimum of 10 degrees through the winter, Salix said.

Kew Gardens is a UNESCO World Heritage site covering 320 acres in the London Borough of Richmond upon Thames, managed by the Royal Botanic Gardens, Kew (RBG Kew).

Heating a glasshouse efficiently is not straightforward. Matthew Vella, senior project manager at Kew, said in an earlier Salix article: "Glasshouses were never designed to be airtight, which makes energy efficiency a huge challenge."

The works

Salix said the project involved drilling an 800m tunnel from the energy centre to the Temperate House. Alternative Heat said it used horizontal directional drilling and was also tasked with delivering new high-voltage infrastructure.

The works were carried out on an open site, and Salix said a forthcoming case study would set out how the team completed upgrades during high footfall periods such as "Christmas at Kew". The project also added ecological measures, including a bird box, a bat box and a hedgehog highway, Salix said.

The opening ceremony brought together representatives from Kew Gardens, Salix, the project design team and Alternative Heat, according to the contractor.

The funding

Salix said in October 2025 that Kew had been awarded funding under Phase 3c and Phase 4 of the PSDS. According to the Department for Energy Security and Net Zero, 209 public sector organisations were awarded grants for 244 heat decarbonisation and energy efficiency projects in Phase 3c.

Alternative Heat lists the project value at £5.3m. Salix's own announcement gives no figures.

The Temperate House is the latest in a series of PSDS-backed projects at Kew. Salix said in October 2025 that under Phase 3b Kew replaced old oil boilers with heat pumps and made fabric upgrades to historic buildings. An earlier project at the Nash Conservatory cost £447,348, with £183,371 of grant funding, and was expected to cut emissions by 30 to 32 tonnes a year after replacing two end-of-life fossil fuel boilers.

Carl Dodd, senior project manager at Kew, said in the October 2025 article that the Temperate House decarbonisation represented a step change in Kew's decarbonisation plan.

What happens next

RBG Kew is working towards a target of going beyond net zero to become climate positive by 2030, Salix said. Kew generated £66m in self-funded income in 2023-24 through admissions, memberships, retail and events, according to Salix.

Kew also holds a Phase 4 PSDS award, which Salix said is introducing air source heat pumps at the Lower Nursery, where rare and tropical plants are grown. Phase 4 awarded grants to 207 public sector organisations for 245 projects, according to the department.

Salix said the Kew team was now planning its next works to stay on track for the 2030 target, and that a detailed case study on the Temperate House delivery would follow.