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building study

The Charter School in Southwark is a new educational institution housed in old buildings that have been refurbished by Penoyre & Prasad Architects to new standards and as a beacon of renewal

The Charter School in the London Borough of Southwark was - whisper it - once a failed secondary school. Then known as Dulwich High School for Boys, its roll sank to 400 and it was completely closed down. But soon after this closure there were calls for a new local school. In 1999 the campaign had built to more than 1,000 parents. Southwark looked at its spread of secondary-school provision, accepted the need, and by May 1999 the secretary of state had approved the creation of what was to become The Charter School.

Starting from scratch as an institution, it was to have its first-year intake of 180 pupils in September 2000 and continue to build the school roll by 180 year-on-year, eventually to include a sixth form.

While the institution got a clean start, not so the buildings. All are being reused, with different degrees of refurbishment, some radical. Budget, timescale and environmental considerations all argued against new-build.

Penoyre & Prasad won the competition for the job in July 1999, leaving just 14 months before the first students were to arrive.

The design challenge was both to upgrade the late 1950s buildings functionally and to communicate the message of a renewed school. The first phase made it for 2000, the second phase was recently completed, except for some landscaping still in progress.

The original school has some architectural distinction, designed by Sir Leslie Martin's team at the London County Council as a campus of separate buildings. The architect is perhaps a bit hard in describing the buildings as 'austere' and the spaces between as 'harsh and unforgiving', but it has a point. Certainly the scheme is typical of its time in terms of open movement between buildings, lack of security across the site, the poorly controlled thermal and daylight performance; typical too is the limited maintenance since the school's construction.

The layout of the original school entrance had something of the country house about it - a long (ramped) loop of road provided a drop-off point at the lower courtyard in front of the main entrance at the school hall block (block D). There were, of course, in practice other points where pedestrians could slip into the buildings. Penoyre & Prasad focused in the first phase on the entrance sequence. There is now only one staff/student entry road (the rest of the road loop just service access) so that pedestrians will come first to block B, a square building around an open square courtyard.

Dealing with the fall in ground level in front of this building, hard landscaping incorporates a descending staircase interlinked with zig-zag ramps providing a fittingly significant approach. You arrive at the building's corner but here the architect has responded by taking a bite out of the building, leading you in with a canted, rendered wall painted purple. Two bands of glazed doors, set back, provide a draught lobby before you enter the courtyard. It is now covered and has underfloor heating. The reception desk opens onto this, now a large multi-purpose space.

Covering the courtyard is the architect's main Phase 1 flourish - much of the tight budget has gone on mending buildings. A tree of five curved steels is set off-centre, rising toward the corner opposite the entrance, the highest roof plane glazed. This ascent is partly for legibility, leading you towards the doors below, which lead on to the rest of the school. Its geometry is also geared to the planned installation of photovoltaic cells (see Environmental Strategy, page 33). And the rainwater recycling from the roof is brought home by the use of transparent lengths in the downpipes against the tree.

Even on a sunny morning after an overnight frost the flow of meltwater was clear to see.

Environmental concerns have been important in the design's generation. The buildings are also intended to have a role in the school's environmental education.

Renewing the site entry and the courtyard building - plus some repairs and maintenance to block C and the gym - were enough to get the school started while the recent phase got under way. Secondary schools are buildings of mass movement after each teaching period. They are also domains where, today, security of students and staff, and thus control of visitors, is high on the agenda. The renewed courtyard building is the gateway for arriving at and leaving the school. Beyond that, where once the school was separate pavilions, the architect has introduced a mix of new enclosed corridors and covered walkways to link them. Only the gym is still detached. Students and staff have swipe cards that deal with security, meal payments and class registration (so the system should know where people are if there is a fire).

As with the entrance ramps, so with the lifts to each block, a virtue has been made of the necessity of providing accessibility. For blocks A, B and C the lift shafts are attached externally, clad in brightly coloured vitreous enamel with glazed tops, another set of beacons of renewal as well as orientation points.

The most dramatic change is a teaching building, block A. You might read it as new, as it almost is. The discovery of asbestos led to it being stripped back to its frame. Unfortunately, the original structures of the school were designed to very tight margins so new partitioning largely follows the original strict cellular, spine-corridor layout. New blockwork is used for its thermal mass.Areas of corridor wall are glazed, providing some openness, borrowed light and the opportunity for visual supervision. Crossventilation and night-time cooling are encouraged by providing classroom doors onto the corridor with electro-magnetic holdbacks.

If the newness of the interior mainly comes from the use of modern materials, mostly plaster and timber, the exterior is a bravura performance. A simple, highly standardised cladding panel system has been transformed by the use of colour, a randomised arrangement of purple/blue panels lightening as they rise up the four-storey building, an abstract evocation of dappled light. The block faces east and west. The extent of new glazing (plus insulation, ventilation and blinds) aims to address overheating risk, rather than using external shading with its penalty of loss of daylight.

To its west, facing the rest of the school, there remains a large projecting bay that now marks the sixth-form common room and is clad bright orange. At four storeys to the other blocks' two or three, the new cladding provides a dramatic backdrop from several points within the site. And in the opposite direction, the roof of the dining/music block (block C) is covered in sedum, improving the prospect from block A's upper floors.

Much of the other work has been smallscale, often caring for distinctive features of the original design, notably timber-tread steel stairs. Some furniture has been made from former lab bench-tops. Generally the muted colour palette has respected the architecture of the original, rather than go for big colour (as, say, AHMM did with its new primary Jubilee School, AJ 1.5.03).

Some staircases and the interior of the nearly new block A are more adventurous with colour.

The other major recent intervention has been in block D, the school hall block. The original school entrance, at the front of this block, can still be used, say where the hall is let separately for performance use. The architect has created a theatrical entry by setting coloured lights along the receding sequence of steps in the ceiling marking the raked floor above.

Inside the hall greater flexibility has been created. The overall layout is level seating, a flat stage area then a raked rear stage, potentially used, say, by a choir or orchestra.

Changing stage level and a lift provided accessibility - there are 12 wheelchair users in the school.An openable acoustic partition allows the rear stage rake to be laid out with chairs as a lecture theatre. When I was there and the remaining theatre was being used for teaching, at conversational rather than full performance loudness, the acoustic screening worked well. (Maybe double acoustic partitioning would have been advisable, as ADP did in its divisible lecture theatre at Roffey Park, AJ 31.7.03. But the budget was very tight here. ) There remains unfinished business. Some ambitions were not met such as additional changing space for the gym (surprisingly, the gym itself is large enough by today's standards). While parapets and fascias have been renewed widely, most cladding is little changed (except of course for block A).

There is a mixture of concrete cladding panels and timber with W20 steel single glazed windows. It is hoped that the other blocks will be reclad over the next few years, though all are aware that other schools in the borough also need money.

The refreshed '60s detailing won't communicate renewal to everyone. But, overall, there is no doubt that Penoyre & Prasad has successfully breathed new life into these buildings, helping create an educational environment which says that students and staff deserved better. And parents think so too. Where once there were protests, exam results exceed the education authorities' (OFSTED) targets and the school is oversubscribed.

ENVIRONMENTAL STRATEGY

At competition stage, it was clear that the programme and budget made it necessary to work with the existing buildings rather than pursue a complete new build.Built in 1956-57 in concrete frame clad in precast concrete, or in steel frame with composite concrete floors and W20 cladding (with substantial areas of single glazing), the existing buildings'environmental performance was very poor.No heed was paid to orientation, with north-facing facades identical to those facing south.However, their sound structure and relatively generous scale made them suitable for improvement. With an awareness that there are many school buildings from this period throughout the UK that are in need of attention, we set out to transform the existing fabric to create a national example of an environmentally responsible school refurbishment and an exemplar learning establishment for the 21st century.

A broad environmental study of the potential/opportunities offered by the site was carried out with Max Fordham & Partners.The strategy that emerged addressed microclimate, rainwater harvesting and slowing of run-off, ways of maximising the solar potential, building fabric upgrade, environmental impact of materials on pupils, use of daylighting to reduce energy consumption from artificial lighting, heating and ventilation. For both refurbished and new-build elements we set high environmental performance targets.Where proposals could not be implemented within the timescale/scope of the works, we ensured that any work we did anticipated future planned upgrades (eg recladding to blocks B, C & D).

Photovoltaics and rainwater collection The large flat roofs of schools from this period are ideal for locating photovoltaic arrays (PVs). A calculation based on the actual useable area of the roofs of the school for positioning PVs (ie areas not overshadowed) gave a total supply of approximately 230,000kWh/y, greater than the electrical energy consumption of the whole school.With increases in the cost efficiency of PVs in the coming years, it may be possible for The Charter School to generate all of its electricity by 2020.

With grant funding the partially glazed section of the new foyer roof may soon be colonised by PVs. The geometry of this roof has been generated by setting a glazed element to face due south and at an angle of 32infinity, the optimum angle of elevation for photovoltaic performance. The remaining three planes are set at a maximum of 15infinity, based on the angle of the sun at midday on the winter solstice, to avoid overshadowing the PVs. The introduction of this new solar geometry acts to re-orientate the school to natural forces.

The use of the roof as a collector, both of solar energy and of rainwater for recycling - the downpipes are transparent - are visible manifestations of the school's commitment to a sustainable future and act as excellent pedagogical devices for increasing environmental awareness.

Summer and winter ventilation

For block A the existing facade was replaced with a highperformance flat skin with greatly increased energy efficiency.Existing school buildings like these typically have problems with summer overheating and a lack of fresh air in winter.Thermal modelling informed the natural ventilation strategy.Permanent shading on the outside can increase the need for artificial lighting. Instead, here solar gain is controlled by high-performance low-E double glazing, and minimising the glazing areas to suit internal functions.For the summer, the exposed thermal mass of the building, and the classroom doors with hold-open stops, facilitate crossventilation and night-time cooling.

For the winter we designed, with SBDS, a system to automatically bring in fresh air without cold draughts.

Behind the radiators are external louvres activated by CO2 sensors.

Ian Goodfellow and Simon Dove, Penoyre & Prasad Architects

CREDITS

COMPETITION WIN July 1999

START ON SITE DATE - PHASE 1 January 2000

LAST PHASE COMPLETION DATE January 2003 GROSS

INTERNAL FLOOR AREA 11,200m2

FORM OF CONTRACT GC/Works 1 TOTAL COST Approx £17 million

CLIENT London Borough of Southwark

ARCHITECT Penoyre and Prasad Architects: David Cole, Liz Crawford, Simon Dove, Ian Goodfellow, Wayne Head, Gillian Horn, Jane Howson, Indy Johar, Simon Jones, Ashish Kumar, Tonja Lauener, Mark Lemanski, Phyllida Mills, Jean Murphy, Sophie Noble, Caroline Osewe, Greg Penoyre, Sunand Prasad, Noam Raz, Sally Rendell, Barry Smythe, Peru Tsen

PROJECT MANAGER Osprey Project Management

STRUCTURAL ENGINEER The Babtie Group

M&E ENGINEER, PLANNING SUPERVISOR Southwark Building Design Services

ENVIRONMENTAL CONSULTANT Max Fordham

QUANTITY SURVEYOR Franklin and Andrews

LANDSCAPE ARCHITECT Watkins: Dally

MAIN CONTRACTOR Mansell Construction Services

SUBCONTRACTORS AND SUPPLIERS Curtainwalling Structura (Heuk), M-Price (Schuco); fascia cladding Dales Fabrications; glazed panels at head of lift shaft Reglit; structural steelwork Hailsham Structures; sedum roof Erisco Bauder; roofing membrane to atrium Carlisle UK; EPDM membrane Firestone; reinforced plasterboard Fermacell; refurbishment paint Keim; acoustic ceiling British Gypsum, Knauf; goat hair carpet Tretford; linoleum Forbo Nairn; rubber flooring Dalsouple; slate Alfred McAlpine Slate; stainless steel rainwater pipes in atrium BM Stainless; drains, couplings Taylor Kerr; ironmongery James Gibbon (Format); furniture, fittings ESA Macintosh; reception desk John Russell Architectural; fixed seating Byproduct; light fittings iGuzzini, Concord; CO2 sensors Smyth & Byford; aggregate external surfaces Sureset UK; hall AV installation Ampekko; access control system Radon

WEBLINKS

London Borough of Southwark www. southwark. gov. uk

Penoyre & Prasad Architects www. penoyre-prasad. net

Osprey Project Management www. ospreymottmac. com

The Babtie Group www. babtie. com

Max Fordham www. maxfordham. com

Franklin and Andrews www. franklinandrews. com

Watkins: Dally http: //wd. noppa-la. co. uk

Mansell Construction Services www. mansell. plc. uk

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