The $80m plan to future-proof Kew Gardens' 175-year-old Palm House

By the River Thames in southwest London lies the Royal Botanic Gardens in Kew. Founded in 1759, it has become a haven for plants and people – from all over the world. 

At its heart is an enormous glass structure called the Palm House. It's home to more than 1,300 tropical plants, usually found in rainforests far away from Britain.

Built in 1848, this Victorian glasshouse now needs renovation – a task that frightens even the architect that won the contract to complete the work.

"I have to say, first of all, I got pretty nervous about it," Hugh Broughton tells CGTN. "The idea of being responsible for at least the architectural design of renovating the Palm House seemed fairly terrifying.

"It's one of the most iconic glass houses in the world. In London itself, it's probably considered one of the top 10 sites in the capital. So a big responsibility."

It's a typically complicated restoration and renovation project for a building officially listed as Grade I – the most protected category in England and Wales. Broughton and his team have to maintain the iron structure, more than 175 years old, but replace the 16,500 panes of glass it contains. 

With sustainability also crucial in modern building projects, the architects must also transform the energy source that heats the glasshouse to between 18 and 22 degrees Celsius, to a more sustainable way.

As Kew's Botanic Gardens are listed as an UNESCO site, advice has been sought from the World Monuments Fund (WMF). 

"It's an icon of its time," says Magnus von Wistinghausen, executive director for WMF Britain, who describes the project as "a very interesting challenge. 

"But I think we've seen with other glass houses around the world that you can meet that challenge – you can substantially reduce energy consumption."

Science and sustainability

Protecting the carefully-curated tropical plants is a scientific necessity, but so is sustainability – and the plan is to eventually create the first net-zero glasshouse of its kind anywhere in the world. 

Toward that goal, electric air heat pumps will heat the building when it's completed – which won't be for a while yet. With confirmation of planning permission expected in December, construction could start in 2027, and this striking building will remain closed to visitors for up to five years.

That's the length of the task awaiting Broughton and his architects, and he sums up the size of the job succinctly.

"We have to make it instantly still recognizable as the very Palm House that people have loved generally for all their lives – but at the same time, people have to look at it and go 'Oh, I can see where they've spent their money…'."

For Rachel Purdon, RBG Kew's Head of Sustainability, it's a cost worth paying to bring this Victorian marvel into a greener future. 

"This timing presents an amazing opportunity," she says. "With new sustainable technologies, we are now in a position for the first time to be able to heat the Palm House using low-carbon, renewable sources of heat.

"This is the first opportunity that we've had as part of a major refurbishment, to be able to replace those fossil fuels with electric heat pumps. "

Cost and opportunity 

Currently, gas is used to heat the Palm House, but the renovation will introduce electric air and water heat pumps. The change will save money as well as helping to decarbonize the glasshouse – a fundamental aim of the renovation process, rendering the choice of glass and seal crucial.

"The Victorians who built this building used all sorts of clever systems of industrialization from that age," explains architect Broughton. "But the reality of it is that of the 16,500 panes of glass in that building, not one is the same size. 

"So each piece of glass has to be carefully cut according to its shape before it can be put back into the Palm House. You can imagine it's a labor-intensive process, and that maybe goes a little bit of the way to explaining why the cost is what it is."

The estimated project cost is $80 million. A third of that sum has already been pledged, with hopes of more to come from some of the Gardens' 2.7 million annual visitors. 

Kew's total income in 2024-25 includes $67 million from commercial trading and charitable activities. And as there's an important scientific element to RBG Kew's work, the British Government's grant-in-aid last year was just over $68 million.

All told, RBG Kew is hopeful of securing all of the necessary funds by the end of 2026, before closing the Palm House for renovation work the following year.

Plants and pumps

The purpose of the Palm House is to maintain the biodiverse specimens, outside their tropical origins. Some of the 1,300 plants – a few of which are older than the 175-year-old building – are already being moved to a temporary, modern glasshouse. 

"There's always a danger that we might lose something," says Alex Summers, RGB Kew's Curator of Living Collections.  

"But the skill level of the horticultural teams we have here, the planning that we've put into it, I would say no. I'd say we have done this down to the nth degree."

It's a huge task but Summers acknowledges the current Palm House needs an update. 

"The reality is that it's deteriorated considerably," he says. "If we look around we can see that, on the metal parts of the structure, on the glass. 

"And if we think that we maintain the temperature in here at 18 degrees C with very high humidity, it shouldn't be any surprise that it's a hard life for it."

As the structure has aged, it has become less efficient – as Broughton's team identified.

"We did a lot of testing to work out how much air is currently escaping out of the Palm House – how we could make changes to the glazing to reduce the amount of air that's escaping out of it," he says.

"We then had to work out how we could carefully remove all the glass, and all the framing for the glass without negatively affecting the big structural arches which support it."

It won't be Kew's first 21st Century upgrade. The Temperate House reopened in 2018 after a $55 million revamp. And in 2026 the smaller Waterlily House will be renovated using the same methods that a year later will be scaled up to the Palm House.

It adds up to a huge but crucial and vital project for one of the planet's most pre-eminent botanic sites. 

"This is absolutely one of the biggest renovation jobs that Kew has ever approached," says Summers. "This is truly one of the most iconic structures, not only here at Kew but globally."