Retrofit and renewal report part two

Image: Norton Folgate, courtesy of British Land

The second part of the report from our 'Retrofit and renewal' forum asked questions around the re-use of building materials for sustainability, how to preserve heritage buildings while updating for office and retail use and the challenges faced by religious institutions over new energy solutions.

This part of the discussion involved British Land on its re-development of Victorian warehouses for new offices in Spitalfields, Pilbrow & Partners speaking about the retrofitting of The Kensington Building and Sheppard Robson describing its work on office re-design at Calton Square in the city centre UNESCO site of Edinburgh. Salisbury Cathedral's Cannon Treasurer, the Rev. Kenneth Padley was invited to discuss the cathedral's journey to net zero and BDP's architect, Christopher Burton commented on both church and Palace of Westminster estate energy solutions.

The recently completed Norton Folgate, developed by British Land, is a mix of Georgian and Victorian buildings, set around historic cobbled courtyards and quiet streets, sits at the meeting point of Spitalfields, Shoreditch and the City. The 330,000 sq ft mixed use scheme is made up of six buildings ranging in size from 10,000 to 120,000 sq ft. Occupiers include Reed Smith, ON, Kolamba, Blank Street Coffee and Xi Home.

Four architects have worked together on the project: AHMM, Stanton Williams, Morris + Company and DSDHA, with the aim of making sure the character and variety of the place is captured in the architecture of the new buildings.

British Land's approach was to carefully restore and preserve the existing Victorian warehouses and facades, showcasing and preserving the industrial features, whilst also delivering new buildings that are sympathetic to their environment and add to the texture of this part of London.

Project director, Lynn Summerfield explained the development approach at our discussion::

'The scale was important. We deliberately chose to have five architects working on individual buildings across the site, so that all the buildings felt different. We had a landscape architect as well. We also used brick across all buildings apart from one and celebrated any interventions.

'We were really clear about the value of the existing buildings with some of the warehouses dating from 1886 through to 1927. We kept the frontages and behind we built new. Although the buildings are in the conservation area, not all the streets are listed but we treated them the same. Some buildings were not kept if they did not have historic elements.

'There was exposed brick work and we had to re-build some existing features, but we kept all the original floorboards. Over the centuries, you can see the pattern of sustainability from the medieval times to the Victorians re-using materials, such as bricks in the division walls that no one would see. Our archaeological dig across the site revealed that in sustainability terms it was the best in thirty years that had been evidenced.'

From Tower Hamlets Council planner, Gareth Gwynne's view, there needs to be credit given to the project:

'Credit needs to be given because none of those buildings are listed and planning could only protect the outside fronts not the spaces behind. The development wouldn't have been anything like it is without the enlightened view that was taken.

'There can be a push these days for modern materials because it is cheaper and quicker and brick carries embodied carbon, so it is horses for courses. However, adaptability is key. Despite whole sets of teams used on projects, the result will work for what we want it to work for, but if the developers or occupants change, that expertise may crumble apart if the building cannot adapt to different uses over time.'

Architect Christopher Burton from BDP commented:

'Policy has a lot to play here. We should value things that already exist in the evolution of place. There should be learning on what is already there to create a more equitable city and a people-focussed city, rather than necessarily always creating something new.

Image: The Kensington Building, courtesy of Pilbrow & Partners

The discussion moved on to debate how architects can remodel tired buildings from the 1970s to create exemplars of modern sustainability for commercial workspace and retail?

Fred Pilbrow, Founder of Pilbrow & Partners, discussed the Kensington Building, a project that involved an upgrading and remodelling a former department store site in London W8.

The practice's completed project for Ashby Capital, remodelled the bleak 1970s building on the corner of Wrights Lane and Kensington High Street, in order to transform the quality of its architecture, public realm and internal working environment. The re-modelling was carried out while the Boots store at street level continued to trade.

The practice described the challenge:

'The project improved connectivity to Kensington High Street Underground station through the creation of a new retail arcade, linking to Wrights Lane.

'The existing building was a purpose-built department store built in the 1970s but occupied principally with offices. The retail was poorly configured and routes to the adjacent Kensington High Street Underground Station were informal through the ground floor Boots unit.

'It was recognised as being of low architectural quality and its large, blank ground floor frontages detracting from the public realm along Wrights Lane. The orthogonal planning of the existing building broke the alignment of the historic street wall, leaving awkward residual spaces on this frontage.

'The proposals restored the definition of the urban block with new facades of Roman brick and Portland Stone. The building scale along this frontage is now modulated as a series of bays – a remediation of the relentless mass of the existing building and a restoration of its civic nature.'

Fred commented:

'It was a pretty ugly department store, Pontings, on Ken High Street, the poor sister to Derry and Toms and Barkers, but nonetheless had good bones. It had really tall floor to ceiling heights and it had really robust regular structural grid. The cladding wasn't great but it could be renewed. We stripped it back to the frame, and built back to the historic street line on Wright's Lane and built up.

'An important part of the conversation has been about how you optimise the use of land well. This is a well connected site next to the tube station, and we doubled the amount of office space (which is sustainable), and made the building more thermally efficient. We introduced a new galleria connection into the Tube public realm, and we are now working with TfL on an over-station development that will deliver step-free access to the underground station.

'The lovely legacy of older buildings can be the generosity of space on the ground floor, so we were able to create a very attractive lobby. We built a new core against the boundary with the Tube, with visible stairs. We encourage people to use the stairs, it's only five storeys. ISG, the contractors, cleaned off all the black paint on the concrete which was a labour of love.

'We set the building back on the upper levels., with landscaped terraces. Manchester United became an unexpected client for taking the space on the these upper floors.

'We are also working on what I think will be the most energy efficient multi-tenanted office building in London, EDGE at London Bridge, It can deliver 57 kilowatt hours per square metre - even with tenant loads - which is better than the BCO's guidance of 55. The Dutch developer has been very open to community access. The ground lobby of timber has a raked theatre space which will be opened up to the local primary school for their Christmas panto /nativity plays. The tenant companies which include law firms have been perfectly happy with this. Everyone has been enthusiastic about this social-community element.'

Image: atrium of Calton Square, Edinburgh, courtesy of Sheppard Robson

Mark Kowal, Partner at Sheppard Robson was asked whether it was concerning that so many buildings in recent decades are now needing to be retrofitted? He agreed:

'It is worrying when you look at some of the age of these buildings. We are doing a lot with 'distressed assets' all over UK. We get a lot of approaches from investment advisers, on how to sort out their buildings, and there is no singular answer. Often it is about the EPC rating that is an 'e' or ''f and needs to get to' b'. but it is also about how office buildings are used, and not just about carbon. These days its also about wellbeing and amenity, and how the building is knitted into a local community and not just about accommodating 'suits'.

'A lot is driven by lease events. We are working with HSBC on the old BT building. They want to be back in the City for talent attraction but the younger generations also love the whole carbon narrative. They love a bit of history but also the embodied carbon piece with all the compromises that come with it. There is a lot of more to come of this type of work.

Sheppard Robson has received planning for the retrofit of a 1990's building in the middle of Edinburgh's UNESCO site. Calton Square is a landmark building in the city centre.

Development manager Ardstone Capital Ltd (UK), acting on behalf of the owners advisor Macquarie Asset Management, has coordinated the project to extend the building from 150,000sqft to 200,000sqft with a series of significant design changes which will align the building to the demands of the modern occupier and provide a significant uplift in the environmental performance of the building.

Mark explained:

'We have taken one floor off the top and added four other floors. We are keeping 82 per cent of the original structure, but demolishing the ground floor slab for level access creating a range of co-working, spaces, lounge and cafe for a dynamic arrival to the building.

'The important thing here is that we are blurring the private and public lines. There is an under-used courtyard and the intention is to bring people into that during the Edinburgh Festival for performance.

'If you were to look down from the top of the building across the city, the impressive element is all the green roofs and terraces that you can see. The yellow stone is being re-used in the building and we are reducing the glazing accents. We are making space for more interesting areas inside.'

CGI mage below of Calton Square with green roof terraces, Edinburgh -: courtesy of Sheppard Robson

The forum also discussed the support given to heritage buildings from parliament offices to cathedrals and involved BDP architect Christopher Burton and Canon Treasurer, the Rev. Kenneth Padley of Salisbury Cathedral.

Ecclesiastical architecture has an important role in providing space for civic and cultural activities as it does for worship, while playing a part in the tourism economy of cities. The forum discussion followed a day after Notre Dame in Paris was opened for inspection following the devastating fire which destroyed the roof and required extensive restoration and cleaning inside.

It costs Salisbury Cathedral some £17,000 a day to run the building and it has taken 30 years to complete the restoration of the roof. There is now a new campaign to restore the North Cloisters that are crumbling away, and a net zero target to meet by 2030. Salisbury cathedral faces retrofitting its heating systems, if it is to reach its net zero goals and has just completed a new lighting system that takes away a large fire risk. The Rev Kenneth Padley said:

'Each church or cathedral is different and will need a bespoke solution. We have the largest close in the country and control most of the properties. We do charge an entry fee and that helps to manage our long term sustainability, but we also have projects such as housing our version of the Magna Carter better for display and our conservation of the roof has been a generation to sort. We do want to be carbon neutral by 2030 and I think we have to be realist about our proposed ground source heat pump scheme. We also need solar panels and insulation. We are not rushing building solutions until the energy system is sorted and there is learning to do. It may involved a combined energy system using gas as well as heat pumps. Some churches will have problems installing ground source heat pumps because they will not be able to bring it through graveyards.'

Kenneth was asked whether the Notre Dame fire raised fears for Salisbury too?

'Well we have just commissioned new LED systems for our lighting, the original system being very consuming and so that has removed a huge risk for us. If I am honest, we need to fire wall the entire roof but that is not realistic. We save money from having our own stone masons. We have reduced the number but those who are with us really know the building and that helps.'

Architect Christopher Burton who worked on a major project for St Martin-in-the-Fields, next to Trafalgar Square, twenty years ago, says there are always challenges with leaking roofs in old churches:

'.These buildings need to evolve. The social responsibility at St Martins-in-the-Fields was huge as was the consideration of its public setting. People forget what it was like. The offering of more public space was very important. It's about engaging with the public and we needed to define the space. As always, it was about recognising the connection back to music. There were leaking rehearsal rooms and it was not attracting the best people to celebrate its legacy. The burial vaults were not suitable for the dead or the living. and the decision was to put something below ground. It's a legacy that sits and plays out and it will evolve.'

Image below: Salisbury Cathedral at dusk, November 2024

Nancy Wood, Director in the sustainability team at Buro Happold commented on the work that her firm had carried out at Bath Abbey on restoring the heating system:

'There was a heating system that was more than 100 years old, and we realised that we could solve some of the problems using hot water from Roman springs. There were concerns over using the grade of water for the heating. However a solution had to be found because the social impact on people is massive and their comfort in the space. was important.'

Buro Happold describes the project:

'The Abbey’s floor has over 8,500 burials beneath it, many of which have started to collapse, making the floor structurally unstable. The building’s 100-year-old heating system was also starting to fail. Our engineers needed to stabilise the floor, install new heating and refurbish the vaults below ground floor level to expand the Abbey’s facilities.

'The Abbey had the unique opportunity to make use of the Bath hot spring water, which rises naturally to a number of sprints and boreholes in the centre of the city. The Roman Great Drain carries nearly 1,000,000 litres of natural hot water from the Roman Baths, which is located adjacent to the Abbey, to the River Avon every day. While this presented an ideal opportunity to provide the Abbey with a sustainable heating system, the water is technically difficult to use in practice due to high mineral and silt content, dissolved oxygen and risk of corrosion, and health risks from pathogenic amoeba. The team needed to propose solutions that would allow the water to be safe and usable.

'To allow the Abbey to use water from the hot springs for the heating system, the team proposed a closed-loop heat exchange system, which can extract 160kW of energy from the water. The heat exchangers provide water at 20-25°C to the Abbey’s electric heat pumps. The pumps in turn raise the temperature to 50-55°C, suitable for under floor heating and trench heating during milder weather.

'It carried out numerous trials and analysis within the Great Drain, including a month-long weir investigation to determine what raised water level was required within the drain to submerge the heat exchangers without flooding the Roman Baths. Work involving the drain was challenging, not only due to the confined space and difficult access, but also gaining the correct approvals. The whole site is an ancient monument area, so a number of different consents needed to be obtained and a new licence agreement was created between the Local Authority and the Abbey.'

Image below: Bath Abbey, courtesy of Buro Happold

BDP has been working on the historic buildings of the Houses of Parliament and the Northern Estate Programme which

comprises the refurbishment and development of multiple Grade I, II and II* listed buildings in Whitehall, providing office space for the House of Commons. Key buildings include Norman Shaw North and South, 1 Derby Gate, 1 Parliament Street and 1 Canon Row.

The programme of refurbishment is necessary to ensure continued security and flexibility of accommodation for the government and addresses poor environmental performance, improves fire safety requirements in order to abide by regulations, enhanced access and circulation, integrated technology and upgraded building fabrics, mechanical and electrical services, workspace, amenities and conference facilities.

Christopher Burton said:

'When I am looking at this project, I am aware that I am looking at a series of buildings and I am asking myself whether I should be concerned with infrastructure or heritage? The best way to decide what to do with these buildings, is to take time to understand them. Take the risk of fire - a lot of challenges are to do with previous ill-conceived adaptations. We need to understand the fabric of the building properly and work with the fabric that is there. We are really engineering the scheme. Once we have the knowledge, we can work from that. The need to make change is in understanding the building.

'As a society we are catching up around the need to conserve these buildings and adapt energy needs, but reducing them and is that a social benefit? Historic England started have a conversation about all this with the General Synod about ten years ago and now that is a new generation working there who are also proactively talking about it. All this discussion will lead to creating sustainability. But it is not just really historic buildings that need the help. There are commercial buildings dating from 2002 that need retrofitting and we have have to value what is there. Clients will have a particular ambition and people will have different opinions. You have to engage with them and listen. It takes time.'

Image below: Northern Estate of the Palace of Westminster and Whitehall, courtesy of BDP

Shravan Joshi, Chair of the Planning and Transportation Committee at the City of London Corporation added:

'We sometimes struggle with heritage and there is no point in preserving it for its own sake. You have to ask how these buildings are used. They have to be viable for modern day use. We have only one net zero church in the City of London for instance. It has a ground source heat pump. But it cost two to three times more than it should have because the heritage bodies were against it. These new energy measures make sense but they cost more from all the resistance along the way.

'We are also looking about how the circular economy works and have our project called 'Romulus'. We know that a steel beam used in the construction of an office building could last two hundred years and could be re-used in several buildings over time and that brings forward a carbon calculation. So the value is not just for today but over the next two hundred years. So we are saying, give us the data as a neutral partner and we will ensure you will get what you need out of that depository.'

British Land's Lynn Summerfield questioned the cost:

'I have been able recently to take floors from one building to another, but now I am realising that the market is catching up and it is alright if you have control of your own supply, but if not, you are paying just the same for heritage materials as you are for new ones. There needs to be some work done to make sure that the maths adds up.'

Future Cities Forum was very grateful to all its contributors who engaged in this worthwhile and productive conversation.

Below: image courtesy of British Land, showing aspects of its Norton Folgate development in Spitalfields