Making Buildings: Lambeth Palace gets a sustainable retrofit

Heritage buildings pose a particular challenge in meeting national net zero commitments. England has around 400,000 listed buildings, where retrofit options are limited, so it is essential to develop workable, high-performance solutions. In that context, the low-energy renovation of Lambeth Palace by Wright & Wright has particular significance: few buildings are as sensitive as the 800-year-old, grade I-listed home of the Archbishop of Canterbury. 

‘Historic England has tracked the project carefully,’ says Wright & Wright partner Stephen Smith as we tour the Thameside complex. ‘They want good examples showing how sustainable retrofit can actually work in practice, and we don’t believe any building of this size and age has been tackled in such a holistic way.’ 

This is the first major overhaul of the palace since it was bombed in the Blitz, and follows Wright & Wright’s 2020 addition of a library tower within its walled gardens. The current project was won in a separate masterplanning competition and had three principal aims: first, general repair of the eclectic collection of buildings (‘everything was falling apart’); second, to repurpose spaces liberated by the new library; and third, to improve energy efficiency. That grew in importance as the brief evolved. In 2020, the General Synod announced that the whole of the Church of England should be net zero carbon by 2030, and the palace is a ‘test-bed’ for strategies that might be applied across its portfolio.

Working with Arup, Wright & Wright adopted a fabric-first approach and developed a plan that could be implemented in stages. The newly complete first phase is concentrated on the 17th-century Great Hall and the 1833 Blore Building. Later phases will cover the Tudor gatehouse, along with older towers overlooking the river, and Victorian cottages housing 130 people on site. The £40 million first phase also prepared the way for future upgrades.  

The most significant example is the site-wide installation of air-source heat pumps (ASHPs), replacing gas boilers that had been housed under the palace’s 13th-century chapel. A new energy centre occupies a service yard tucked away on the edge of the complex, where three giant ASHPs sit hidden behind metal screens. 

One ASHP is sufficient to supply buildings renovated in the first phase, and the second will cover the remainder. The third is a back-up. From the energy centre, a 2km network of pipes radiates out across the site. Where they lead to unrenovated buildings, plate heat exchangers allow compatibility with existing plumbing. 

Routing the pipes was a delicate operation. Wright & Wright mapped the history of the site to anticipate the location of archaeological remains, which were duly uncovered in the excavation of the shallow trenches. Most pipes are below courtyards, but pass through one historic building to keep an adjacent archway open during construction.

Extensive research also informed the renovation of buildings. The Great Hall, now an events space, had been a repository for the palace archive since the 1830s. Referring to its more distant past helped to make the case for conversion, but Wright & Wright was nonetheless determined to retain existing fabric, and bookcases installed in the 1940s have been recomposed as panelling, complete with original caps and trims – ‘Part of our circular economy,’ says Smith. 

New trench heaters in existing floor voids run off the ASHPs, and the temperature now rises above Conservation Heating standards. Overhead, the twisting timbers of the gothic hammer-beam roof have been painstakingly checked and stabilised – an unexpected task necessitated when a cornice fell from height shortly before construction work began.

The newly accommodating hall reflects a desire to open more of the palace to the public, also supported by the relocation of kitchens from a stygian basement to rooms nearby. The high-spec, industrial-scale electric facility gives another big carbon saving, says Smith, and can feed up to 2,000 people. 

The most significant alterations were made to Blore Building – the palace’s administrative hub. On the raised ground floor, the Archbishop’s offices are flanked by grand state rooms. Below are shared offices, while the top two levels provide guest bedrooms. ‘It is the biggest and most intensively used building, and also the youngest and most easily changed,’ says Smith. 

Outwardly, the only visible alterations are modest additions to improve accessibility. Curved stone ramps now allow all visitors to use the front door, and a lift overrun has been accommodated by rebuilding a 1960s ‘infill’ structure nestled against the Great Hall. Faced in stone and with a lead roof, it blends comfortably. 

Another significant change goes unnoticed: replacement of all 160 windows accounts for much of a 40 per cent reduction in energy demand. Here, the architects were lucky. Following wartime bomb damage, original windows had been replaced with inauthentic leaded lights. ‘We were able to tell Historic England that reinstating sash windows is a benefit rather than harm,’ says Smith, ‘and could double-glaze with airtightness seals while restoring the building to its original appearance.’ 

As windows were critical to the larger strategy, Wright & Wright had detailed discussions with suppliers at an early stage, and included details of several potential types in the planning application. The chosen profile is used for all windows – mostly in wood, but with a steel version for the main stair. Considerable variation in size was addressed by laser-scanning the whole building. Though the box sashes are relatively thick, they sit neatly in existing reveals. 

The job was given to to SB Joinery, which Wright & Wright knew through previous renovations that also forged useful connections with specialists in plaster and stonework. It was a large order for the firm. ‘With this kind of project, it’s good to have subcontractors who are a bit out of their comfort zone,’ says Smith, ‘but are pushing themselves to prove what can be done.’ 

Inside, the first-time visitor would hardly suspect that the building has been ‘gutted’ (as Smith puts it) and recomposed to meet present needs. Staircases were rebuilt, and timber floors on the lower levels reconstructed to create level access and allow the addition of insulation. More insulation was added in the relaid roof, though not to walls. ‘That’s a no-no for listed buildings unless they are very plain,’ says Smith, ‘because you have to change decorative features.'

Interiors look closer to their original condition than at any time since the war. The architects rediscovered original paint records, and cold blue-grey walls have been repainted in a warmer stone colour. And where existing plumbing was surface-mounted, new larger-bore heating pipes required by ASHPs are discreetly concealed. ‘We were conscious of the fear that sustainability is going to damage listed buildings, so hiding it became like a mantra,’ says Smith. 

Existing pipework rose from the boiler to the roof then dropped down through a series of risers before snaking back through asbestos-lined channels on the ground floor. ‘Completely bizarre,’ says Smith, ‘but useful as we could reuse the risers in a more logical way, as flow-and-return loops from the ground floor. And because the building is so chunky there was room to super-insulate the pipes.’  

Other technologies tested here include greywater recycling and some rooftop photovoltaics, but the cost-benefit analysis showed limited energy savings in this setting, says Smith. 

This mix of pragmatism and ambition has seen annual CO₂ emissions drop from 647,000kg to 233,000kg following the first phase, set to fall to 81,000kg when all proposed works are complete. The final stretch to net zero will be covered by offsetting, but it’s a destination the church says it is determined to reach – both for the immediate practical benefits and to demonstrate responsibility in the creation of a more just world.