Sheffield's future vision

Will the Winter Garden and Millennium Galleries promote regeneration? asks Neil Jackson, professor of architectural engineering at Leeds University.

For all its bawdy humour and pathos, the film The Full Monty pictured a Sheffield which many of its citizens would have preferred to forget. Like its cutlers and grinders, that city has largely gone and what is now emerging through Sheffield’s regenerative Heart of the City project is a vital, sensitive and vibrant living place.

This is being achieved through a slow process of regeneration dependent on the careful reintegration of the city’s fabric. Central to this are the £17.5m Millennium Galleries and Winter Garden designed by Pringle Richards Sharratt. Won in competition in 1996 and completed, respectively, in April 2001 and December last, the Millennium Galleries and Winter Garden stitch together a series of cultural and civic monuments and turn a sometimes wet and windswept incline, rising from the old inner ring road to the town hall, into a sequence of welcoming public spaces which now hum with life. ‘It has met our expectations and exceeded them’, says the city council’s head of leisure services, Keith Crawshaw. Gordon Rintoul, former chief executive of the Sheffield Galleries & Museums Trust, is equally impressed: ‘in a very short time the galleries have become part of the fabric of the city and an element of the lives of the local people’. Even before the Winter Garden opened, annual visitor numbers to the galleries exceeded by two and a half times the original estimate of 160,000 and now the City Centre Ambassadors, Sheffield’s uniformed public guardians, congregate in the winter garden rather than monitor the streets.

If there is something slightly familiar about this architecture it must be because, between them, John Pringle and Ian Sharratt worked for almost 40 years for Michael Hopkins & Partners, while Penny Richards came through Rick Mather’s office. Thus there is a sense of care and craft about these buildings, plus an uncompromising attitude to modernism and sustainability. But the solutions are their own and specific to the situation.

Together the Millennium Galleries and Winter Garden form a T-shaped plan. The galleries, which form the leg of the ‘T’, rise up the hill from the much-contained thoroughfare of Arundel Gate, parallel to Surrey Street with the central library and Graves art gallery, towards Edward Mountford’s 1890s town hall at the top. The Winter Garden occupies the former site of the ‘Egg Box’, the 1970s precast concrete town hall extension by city architect Bernard Warren, forming a cross axis which links Tudor Square and Renton Howard Wood’s 1972 Crucible Theatre to the revitalised Peace Gardens and the circular registry office. The new buildings are predominantly inward-looking and the experience they offer is primarily internalised, making good use of borrowed light and reflective surfaces.

Approached from Arundel Gate by escalator and a glass lift, the galleries are arranged as a series of parallel, concrete cross vaults, recalling Kahn’s Kimbell art museum in Fort Worth, Texas. Whereas Kahn famously brought the light in through a reflective trough at the centre of the vault, here the light is bounced off the polished valley gutters that run between the vaults – a solution that works just as well. As at the Kimbell, the separating walls are removable and the space inherently flexible.

The first six bays are given over to temporary exhibition space, whereas the rear six comprise the metalwork gallery, the craft and design gallery, and the Ruskin gallery. Each gallery opens informally, like a shop front, onto the Avenue, a 75 metre long internal foyer. Here glass blocks and fritted glazing reduce light levels to 50 per cent in preparation for the 10 per cent required within the galleries, while hypocaust floors and cavity ducts circulate air from the plantroom below. With more than a memory of Hopkins’ Inland Revenue headquarters at Nottingham (AT56), the heavy concrete vaults provide a stabilising thermal mass overhead. But unlike the Inland Revenue, these vaults are precast in two quadrant sections, which together span 14.4 metres, and post-tensioned. Much of the structure and envelope was fabricated in mainland Europe. The precast concrete, made from light-reflective crushed marble and micaceous sand, is Dutch; the glazing is Belgian; and the terne-coated stainless steel roof is French; with sterling strong against the euro, apparently no Sheffield steel firm could do the roof for less.

It was, similarly, a German timber firm that supplied the great parabolic arches for the Winter Garden. The architects had previously used this supplier, Merk, at Shrewsbury music school (AT120). Made from laminated larch, and reaching to 22 metres at the centre, the parabolas frame a grand and dignified space 67.5 metres long and 22 metres wide. The rectangular-section arches spring in pairs from great galvanised steel shoes, a memory perhaps of Peter Behrens’ AEG turbine factory in Berlin, before splaying out, with one arch accommodating the higher vault and the other the adjacent, lower vault, thus allowing the roof to rise up to the centre before stepping down again. Circular-section laminated timber struts also run diagonally up to the gutter, a broad, horizontal plate girder at the level of a side-aisle roof, to provide lateral bracing, while secondary parabolic arches rise from their point of juncture. All around, the roof is a simple 600mm single-skin patent glazing system with opening lights.

As at Paxton’s Crystal Palace, the laminated timber arches enclose trees, but here in a didactic rather than expedient arrangement. Exotic trees and bushes populate the raised beds: Japanese sago palm is one of the ‘plants the dinosaurs ate’, whereas Norfolk Island pine and New Zealand flax explain how Captain Cook hoped to refit his ships in the south Pacific in 1779. The fact that the building stands on what was the Duke of Norfolk’s estate (witness the adjacent Norfolk Street) adds another layer to this history lesson.

Although currently the laminated timber arches form a fine backdrop to the Peace Gardens, they will eventually be hemmed in by a new hotel. This, and the extension of the public plaza to the south-west, are the outcome of the various masterplans to which the architects have had to respond. It must have been difficult to design for such an ill-defined context. Unlike another of Sheffield’s Lottery-funded projects, Branson Coates’ ill-fated Centre for Popular Music (AT97), Pringle Richards Sharratt’s solution is anything but an object building. Nonetheless it may well become a signature for the city: for the regeneration of city centres is achieved by a gentler understanding of how cities, and their people, really work.

Chronology:
1994-95 Allies & Morrison masterplan for the city council forms first bid to Millennium Commission.

1995-98 Terry Farrell & Partners prepare masterplan for Taylor Woodrow, the council’s PFI partner for its new offices and the commercial parts of the £120m Heart of the City project. Definitive bid to Millennium Commission on basis of Farrell masterplan, with the site for Millennium Galleries/Winter Garden identified.

1996 Pringle Richards Sharratt appointed architect for MG/WG.

1998 Peace Gardens, by Sheffield City Council architects, open.

1998-99 HLM design new council offices to replace 'egg box'.

2000 Koetter Kim’s masterplan for Sheffield One (including MG/WG site).

2001 Millennium Galleries open. Aukett prepares new masterplan for London & Regional, who took over PFI element from Taylor Woodrow. Hammerson with lead architects BDP appointed as preferred partner for £350m retail quarter.

2002 Winter Garden opens in December. Allies & Morrison prepare new masterplan for CTP/St James Securities, new developer of the commercial element of the project. Planning application for Macdonald hotel adjoining WG by Weintraub Assocs.

Pringle Richards Sharratt write:

The project is conceived not as an object in an open city square but as a series of streets and spaces ‘mined’ out of a dense bit of urban fabric – an arcade running through the middle of a city block surrounded by other buildings. The building is thus seen as part of larger urban configuration and its interior is intended to be a seamless part of the urban landscape, providing a cultural route through to the city centre. The key elements are the covered arcades – the Winter Garden and the Avenue – which run through the site surrounded by a variety of interesting spaces. The arcades connect inside and out and also provide links between three of Sheffield’s main public squares.

The Winter Garden is a spectacular glazed public space in the heart of the city centre. Extensively landscaped with exotic trees and plants, it is an indoor park providing an important amenity for the public and a counterpoint to the open-air Peace Gardens nearby.

The building, 67.5 metres long and 22 metres wide, rises from either end in a series of steps to a lofty 22 metres over the three central bays. Here, in a central court, the Millennium Galleries seamlessly connect into the building and the tallest growing plants are located.

Along the length of the building three garden areas have been formed, two of which have paths which wind their way through the trees and plants and past small water features. The building is paved throughout with local gritstone, which also provides the supports for the benches distributed throughout the space.

The Winter Garden steps down at either end to relate to the height of existing buildings. It rises toward the centre to provide height for the taller plants, a sense of drama to the interior and to define and express a central court or gathering space opposite the Millennium Galleries.

The structure of the Winter Garden is clear and legible and the forms and materials are both natural and familiar. The scale is spectacular, providing a memorable experience for all visitors, young and old alike.

The beds rise by up to 600m above finished floor level with a further 500mm provided by a 12m wide downstand ‘trough’ which extends along the length of the Winter Garden. This produces a maximum bed depth of 1100mm, large enough for the rootballs of the taller trees. The building is supported on a concrete structure over the parking and delivery facilities for the Millennium Galleries.

In the Millennium Galleries there is no hierarchy of galleries, but rather a great variety of spaces set in a strong permanent framework provided by the exposed structure. The exhibition spaces are designed to be responsive and flexible, so that their character can change according to the exhibition. In contrast the structure is unchanging and substantial. The heavy, thermally-massive vaults are engineered to ‘hover’ overhead, barely supported above clerestory glazing that admits reflected light into the galleries. Air is circulated through cavities in the structure, cooling the hypocaust floors, rising under its buoyancy to reservoirs in the vaults and returning down through shafts to the air handling plant below.

All the public gallery spaces are at the upper level (the same level as the Winter Garden). The Avenue, a 75m long public foyer, runs the full length of the building, serving both as an orientation space for the galleries and a link between the two ends of the building. Escalators and a lift provide easy access to gallery level bridging the 5m level difference between one end of the site and the other.

The 1,500m2 of exhibition spaces are highly flexible, capable of subdivision into smaller spaces with movable partitions. Offices and education spaces are housed in Leader House, a listed building, linked to the mid-point of the main route through the gallery. All support spaces are one level below the galleries, serviced from the underground service road below the Winter Garden. The cafe occupies most of the Hallam Square frontage and is reached from the lower foyer; seating can extend onto the terrace in front of the gallery, facing Hallam Square.

Structure, services, lighting systems and architectural finishes in the Millennium Galleries are highly integrated. The thermal mass of ventilated internal walls and hypocaust floors acts as a thermal ‘sponge’, slowing down heat gains; their radiant effect also improves comfort conditions and reduces air conditioning loads. Ventilation is a floor-supplied displacement system.

The roof consists of white, ribbed precast concrete barrel vaults spanning 15m across the gallery. A clerestory band runs around the perimeter of each vault, admitting natural light into the gallery, which is bounced off reflectors in the gutter and roof verge and the white surface of the concrete vaults. Natural light is controlled automatically by motorised venetian blinds in the windows. The external envelope (particularly the roof) is highly insulated and provides shading against solar gains, whilst admitting north light to reduce lighting costs and heat gains. The building’s structure was manufactured in precisely made precast concrete units (in Holland) and ‘stitched’ together with only a few litres of in situ concrete on site. The main roof vaults are post-tensioned folded plate structures spanning 14.4m, prefabricated in two halves.

Structure and services

The Winter Garden structure is formed by a series of timber arches formed from glue laminated (glulam) 50mm strips of European larch, writes Buro Happold. The largest component brought to site was 24m long and 900mm deep, far larger than any larch tree. While the material is not new, in some cases the design was beyond the scope of UK design guidance, resulting in the use of European and German technical guides.

The requirement to maximise the internal space without internal supports led to the development of glued laminated timber parabolic arches at 3.75m centres. This is not only a very efficient structural form but also provides a large enclosed volume allowing flexibility in the planting height and layout. The concept of inverted catenery profile arches was developed to achieve predominantly axial forces with low bending moments. This gives an extremely efficient structural form, reduces the material used and results in a structure ideally suited to engineered wood.

The larch, derived from sustainable forests, requires no preservatives or coatings. This reduces the use of solvents and also avoids the use of chemicals that could kill the plants.

A study of the environmental impact of constructing the building showed that timber had an eco-rating less than five per cent of that for steel or concrete alternatives – ie offering a 95 per cent reduction in energy used in construction. In addition, savings could be made in the foundations, as the weight of glulam is significantly less than steel or concrete alternatives – about 65 per cent of the weight of a steel, and 15 per cent of a concrete, alternative. The building is single-glazed with over 1,400 framed roof panels, of which 128 open for ventilation. The ventilation panels are all the same size, as are over 80 per cent of the fixed panels.

The environmental strategy has been linked closely to the diverse species of plants and the need to maintain frost-free conditions. These results helped to inform the envelope design including glazing specification, shading devices and ventilation openings. The Winter Garden is a frost-protected temperate environment. In winter it provides protection against rain and wind and conserves heat gains from the surrounding buildings and the sun. High-level fans prevent stratification and induce air movement within the building, helping to equalise the temperature and minimise the risk of fungal growth, which would adversely affect the plants. For cold winter nights, underfloor heating prevents frost within the gardens, allowing a wider variety of vegetation. The primary heating is provided from the city’s district heating main.

In summer, surrounding buildings provide solar shading while the high-level operable windows, together with opening glass louvres at either end, maximise the natural stack-effect ventilation and induce evaporative cooling from the plants. Small water features help modify local humidity levels. The louvres also provide smoke ventilation in the event of fire.

The design solutions would not have been possible without the use of fire engineering. Smoke control systems enable the Millennium Galleries and Winter Garden to be open spaces without the need for compartmentation. A natural ventilation system was used for smoke clearance in the Winter Garden, taking advantage of the natural system provided for the environmental strategy and accounting for adverse wind effects. A risk assessment showed that fire-resisting glazing to the Winter Garden was unnecessary and that toughened glazing achieved the required compartmentation performance.

Project team

Architect: Pringle Richards Sharratt; Winter Garden design team: John Pringle, Penny Richards, Ian Sharratt, Douglas Oyugi, Basil Kalaitzis, Adam Blacker; Millennium Galleries design team: John Pringle, Penny Richards, Ian Sharratt, Douglas Oyugi, Basil Kalaitzis, Adam Blacker, Joanne Metcalf, Valerie von Truchsess, Therese Degermark, Tim Gledstone; qs, project manager, planning supervisor: Sheffield Design & Property; structural/services engineer: Buro Happold; fire/access: Buro Happold/FEDRA; acoustics: Arup Acoustics; lighting: Bartenbach LichtLabor/Lichttechnik Martin Klingler; exhibition design: Jasper Jacob Assocs, Ralph Appelbaum Assocs; glass artist (Ruskin Gallery): Keiko Mukaide; Winter Garden landscape: Weddle Landscape Design; management contractors: Interserve Project Services; Leader House refurbishment: Graham Stuart Construction; client: Sheffield City Council, Sheffield Galleries & Museums Trust.

Selected subcontractors and suppliers

Winter Garden: substructure: Hewlett; laminated timber structure: Merk Holzbau; Vitral glazing supply/installation: J&W Haran; roof access system: Clow Group; paving: Graham Stuart Construction; paving adhesives: Ardex; benches: Corin Mellor; plants/water feature: Rentokil; roof glazing actuators: SE Controls; louvred glazing: PHP Glastec Systeme; underfloor heating: Velta; roller blinds: Maple Sunscreening; sealants: Dow Corning; automatic doors: Geze; ironmongery: Dorma Door Controls; locks: Assa; m&e: Powerminster; temporary hoarding: Panelock System; signage: Widd Group; balustrades: Beeley Fabrications; stone: Johnsons Wellfield Quarries; lighting: iGuzzini, Holophane.

Millennium Galleries: pc structure: Hibex BV, Klomp BV (erection); structural steel: JP Fabrications; roofing, rooflights: Kelsey Roofing Industries; terned stainless steel roof: Eurocom Enterprise; roof membrane: Flag UK; roof glazing: Coxdome; external glazing, lift shaft enclosure: Soliver Waregem; aluminium-framed glazing: RC Systems; bolted glazing: Structawall, Glas & Metaal Engineering; automatic sliding doors: Geze UK; glass blocks, terrace: GBW; glass blocks: Solaris; glazed blockwork: Forticrete; external louvres: Western Avery; m&e: NG Bailey; passenger/goods lift, dumb waiters: Independent Lifts; scissor lift: RS Stokvis; escalators: Schindler; internal glazed screens: In House Design; raised access floors: Atlas Access Floors; raised floor tile: Alumasc Interior Building Products; ventilation louvres: Glidefield; joinery: Sheffield Direct Services; architectural metalwork: Beeley Fabrications; spiral staircase: Albion Design; glass balustrade: Sovereign Stainless Fabrications; security grilles: Troax (UK); sliding/folding partitions: Panelock, Alco Beldan; drylining partitions, washrooms: JDM Contracts; plasterboard: British Gypsum; floor finishes: Q Flooring Systems; Quarella floor tiles: Concept Tiling; wc wall tiles: Shackerley Holdings; shower tiles: Buchtal; sanitary fittings, wc accessories: GroheDal, Armitage Shanks, Keramag, Hewi, Laufen, Duravit, Ideal Standard, Warner Howard, Amwell Laminates; FSB Allgood ironmongery: Lloyd Worrall; locks: Assa; decorations: Foyle & Kirk; floor paint: Hesselberg Barrikade; window cleaning equipment: HCL Safety; clerestory blinds: Screenline (UK); internal blinds: Levolux AT; external works: Sheffield Direct Services; gallery fitout: Graeme Ash Shopfitters; plaster, render: Horbury Building Systems; sealants: PJ Sealants; lighting: Concord-Marlin, iGuzzini, Artemide, Erco, Thorn.

Link: Architecture Today

© Architecture Today 2003