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Design for learning

Feilden Clegg's Berrill Building for the Open University in Milton Keynes is an elegant and efficient landmark building. It is also an exemplar of low-energy design, achieved within tight budget and programme constraints

Client's account

RICHARD BAILY Director of estates, OU Since its inception in 1969, the success of the Open University has led to the regular construction of additional buildings on the main campus at Walton Hall, Milton Keynes. The Estates Strategic Plan identified a potential major shortfall of space by 1998 and a decision was made in 1995 to construct 5000m 2of additional, mainly office, space.

Based on an outline brief, competitive bids were sought for project management services, and bidders asked to recommend a method of procurement. Mace was the successful bidder, having identified a design team that included Feilden Clegg. The practice impressed the university with its innovative design ideas and experience in low-energy buildings. Mace recommended a construction management approach, for which it was also appointed.

The Berrill Building houses the university's knowledge media institute, Open University Worldwide, students' services and public relations, together with visitors' reception, and has fulfilled the objective of providing a landmark entrance and showcase for the university.

Architect's account

PETER CLEGG Feilden Clegg Architects Universities are dynamic organisations. Their development can be either frustrated or facilitated by the buildings they occupy. The brief we were given for the OU's entrance building highlighted the need for a new type of building to encourage changes within the organisation. The OU is a 'virtual' university, founded by Harold Wilson and Michael Young long before the word took on its current meaning. It is the biggest university in the world with 450,000 students, but it has no campus. Its administrative HQ, with hardly any students, was set out in the 1960s as a loose grid of courtyard buildings, typically three storeys high and 9m deep, providing cellular office accommodation across quite a large site.

We were asked by the OU masterplanning architect, John Thacker, to address a different brief, one requiring almost entirely open-plan accommodation and therefore demanding wider floorplates, and one which brought together the main administrative functions of the university into one substantial building on a small part of the site.

This building was also to provide a new entrance to the campus, enhance its public image, and, by converting a redundant BBC studio in an adjacent building, provide high-quality conference facilities that are lacking on the campus.

All these changes in organisation and function suggested a change in scale. The small-town campus architecture needed to take on a more urban scale, and we became convinced that a five-storey building - and five tall storeys at that - would be an appropriate response to the site and brief, and would generate a building that clearly announced itself above the tree belt surrounding the site to provide a landmark in Milton Keynes.

The main office building, on a north/south axis along the eastern boundary, is linked to the existing studio building by a glazed concourse. This accommodates a ground-floor cafe opening on to adjoining courtyard spaces, and a conference reception area on the mezzanine above, connecting to the main entrance at first-floor level. The entrance is accessed by a ramped bridge from the car park into a five-storey atrium entrance hall from which the main vertical circulation and principal office meeting rooms are organised.

The demand for a wider floorplate necessitated careful consideration of the potential for overheating. The client wanted as green a building as possible - air-conditioning was not an option.

Our experience working on the New Environmental Office for the BRE was very valuable. Avoidance of overheating requires a high degree of exposed thermal mass, primarily by avoiding suspended ceilings, increasing floor-to-ceiling heights to ensure adequate cross-ventilation paths, and using external blinds to reduce solar gain. Internal gains from lights were reduced by photo-cell controls, and provision for cross-ventilation was maintained even when cellular offices were installed by ensuring that cellular spaces had a lower ceiling to enable the ventilation paths to the main office to pass over it.

The building depth is 14m and the floor-to-ceiling height 3.2m (2.6 to the underside of beams).

These dimensions came from our own experience as well as that of Buro Happold and analysis of recent good-practice guides such as that produced by the BRE. The top floor, which offers more opportunity for both introduction of daylight and ventilation through clerestories in the roof, means floor depth can be increased to 18m and allows for a row of cellular offices down each side while maintaining cross-ventilation through clerestory windows above. The aerofoil section of the roof maximises indirect light into internal spaces, and gives a simple unifying character to the largest floorplate of the building.

To achieve this within a restricted budget, we selected a simple planning system, with large-scale opening lights (2.4 x 0.8m top-hung projecting vents). The basic curtain-walling system with standard white spandrel panels is partially concealed, and enriched by a layer of external solar shading. On the east elevation this consists of permanent vertical 'blinkers' which are suspended offset towards the windows from the line of the structural columns at 3m centres along the facade.

On the western elevation we used photo-cellcontrolled external roller blinds suspended on the outside face of the access walkway system. Although the external blinds reduce solar gain, we did have to use the budget that the client had set aside for internal blinds to supplement glare control on both elevations.

The OU put its trust in the construction management process. Designed to provide the best value for money from the design team and specialist subcontractors, CM is based on a co-operative approach suggested by Latham. The client's confidence was vindicated when the project was completed satisfactorily on time and on budget.

The university is adapting to the building, and the cultural change it implies. There is a need for evaluation of the environmental performance of what we hope will be a precedent for low-cost/energ y office buildings.

Structural engineer's account

TIM MANDER Buro Happold The main office floorplates are 14m in width and downstand beams or ribs at 3m centres clear span the floor. The ribs act compositely with the slab, resulting in 'T' beams. The main floorplates are naturally vented across the building and the ribs run parallel to the direction of ventilation. To assist cross-ventilation and maximise light penetration, the columns are at beam centres, giving a clear free edge to the building.

The building is aligned in a north-south direction and to shade the offices from the low-angle sun, the columns are sculpted forming 'blade' columns. The exposed in-situ concrete slabs, beams and columns generate the thermal mass. Precast concrete was proposed but the frame contractor offered savings by incorporating in-situ concrete throughout.

At fourth-floor level the beams project beyond the building line and shading systems hang from the projecting beams. Steel bowstring trusses span the fourth floor.

Environmental engineer's account

TONY MCLAUGHLIN The text-book answer to 'low-energy' planning is rarely achievable - something usually has to be compromised, and so it was with this building. The orientation is not ideal, with main facades facing east and west, as a result of site dimensions and its relation to the existing BBC building which connects to it. Also, the building's size overshadows existing buildings, although a BREEAM rating of 'very good' has been achieved.

There is high IT usage, so thermal mass, external shading (secondary internal shades were added post-contract), controlling lighting-load outputs, and generous floor-to-ceiling dimensions were critical in controlling summer temperatures.

The scheme is predominantly naturally ventilated.

Window opening is a mix of low-level manual and automatic high-level control, which can be overridden by occupants. A night-cooling strategy controls the high-level ventilation. If these elements are operated, summer temperatures can be controlled as illustrated in the diagram.

The lighting strategy is a reduced version of the tendered scheme - but is still responsive and efficient, responding to occupancy patterns and natural light penetration. Lights are switched on by occupancy sensors, and react to measured light levels within the rooms. At present the control regime is set to maintain uniform luminance of 350 lux; as daylight intensities increase the fittings are automatically dimmed down to maintain a pre-set level. Dimming can go down to 10 per cent of the fitting's power. This does mean that artificial light will always be on during the day where there is movement, albeit at a very reduced level. The light fittings have an upward lighting component illuminating the exposed concrete, so the fact that a reduced lighting element can be maintained at all times provides visual uniformity to the spaces.

The building uses the campus district heating scheme, eliminating the need for boiler plant and chimneys. Heat is distributed around the building system, being zoned east, west and per floor. Only the refurbished lecture theatre in the existing BBC building and the two small computer rooms are mechanically cooled.

Appraisal

PROFESSOR DEAN HAWKES Welsh School of Architecture From the very earliest days, the work of Feilden Clegg has engaged with the specific issues of each project - the fundamentals of brief, budget and place. This has been consistently conditioned by environmental consciousness. It is a rational, undogmatic approach in which the ephemera of fashion have little place but which, when executed with judgement and invention, produces buildings of substance. The Berrill Building eloquently demonstrates the potential of the formula.

Talk of university buildings usually calls to mind the collegiate splendours of Oxbridge, the expression of Victorian civic pride in the 'red-brick' colleges or the social-democratic vision of the 'new' universities of the 1960s. In all of these the institution is given its most concrete expression and identity through the architecture of its religious, cultural, teaching or residential buildings. It is no accident that most university prospectuses contain images of significant buildings as essential icons.

The Open University is different. Its basis in what is now called 'distance learning' means that there is no need for the physical infrastructure of the conventional university. Hence the familiar association of institution and architecture does not exist. Within the grid structure of the New Town the site is analogous to the industrial areas, or more particularly, to the business 'parks' of the city and, as is the way at 'MK', it is entered off University Roundabout. Although there are a number of specialist buildings on the site, most of the accommodation takes the form of office space, and the Berrill Building is the latest addition. It is in many ways a corporate headquarters building and, as such, is far removed from the conventional history and tradition of university building.

In the post-war years the British office has passed through a complex process of architectural evolution. In the 1950s the curtain wall replaced the brick facade. The shallow-plan, daylit, naturally ventilated designs suddenly produced a range of environmental problems. Buildings with little thermal mass and minimal insulation suffered from summertime overheating, enormous winter heat loss and thermal discomfort. Office workers complained of glare and of the acoustic problems which followed from the need to have windows fully open on to city streets in the summer months. In response, the office environment was progressively mechanised as air-conditioning became the norm and new relationships between building fabric and mechanical systems were explored. By the late 1970s it was almost inevitable that an office building would be deep-plan with full air-conditioning and, in most cases, permanent artificial lighting.

The growing concern with energy costs then propelled thinking towards other solutions. A key factor was the revival of daylighting as a means of making significant savings. As first conceived, the atrium office, in such designs as Arup Associates' Gateway Two (AJ 3.83) was an elegant solution, but, sadly, many of its progeny have proved more concerned with image than substance. The other approach to the low-energy office is to return to the daylit slab. This provides the basis for the OU's n ew building.

At first sight the building might seem unremarkable. But its apparent simplicity conceals a deep understanding of the issues. What we have is the shallow-plan, daylit, naturally ventilated office building of the late 1950s, revisited and completely transformed by the understanding of the potential of natural environmental processes which we have gained in the last four decades. There are two main dimensions to this transformation: the design of the building envelope and of the plant and its controls.

The simple in-situ concrete structure provides column-free space. The slender and deep perimeter columns act as a transition in brightness from exterior to interior, very much as the splayed reveals of a Georgian window do. The concrete soffit supplies thermal mass and the raised floor allows service distribution. The elegantly detailed curtain wall is double-glazed with well insulated spandrels. Each facade has a layering of shading devices and maintenance access, subtly different between east and west in response to the different thermal loads at each orientation.

To achieve proper environmental control a building must be understood as a system of interconnected elements and processes. At the OU this is achieved in a number of ways. The natural and artificial lighting are integrated through both light-level and occupancy sensors on the luminaires and, on the thermal side, the high-level opening lights are temperature-activated for summer ventilation, but are inoperable when the heating system is active to avoid excessive ventilation heat loss. Low-level vents, however, are user-operated to allow an element of individual control.

The outcome is a building which, through clear and systematic thought, makes an important statement about environmental design. It should be seen as an exemplar for many of the office projects in which tight constraints of programme, context and budget might be assumed to mitigate against efficient and elegant design. This is, however, not just a matter of technical expertise. The building pulls off the difficult trick of making eloquent the necessary. The overhang of the zinc-clad top storey gives positive termination to the facades and the sweeping entrance bridge engaging with the angle flank of the stair and lift tower are nicely juxtaposed with the orthogonal repetitions of the gridded facade. In its composition, proportion, materiality and detail, the building is an elegant statement of its own nature and, standing prominently at the gateway to the campus, an appropriate icon of the Open University and its status as one of the great events in the history of higher education in this country.

Cost comment

ALAN ROBINSON Mace The cost plan was approved by the client in August 1995 and prices fixed at second-quarter 1995 rates. The project was originally intended to be let under a traditional JCT form, but it was demonstrated that there were significant advantages to be gained by following a construction management route which incorporated full financial control. This would not only reduce on-costs but also, by using the procurement methods of construction management, would ensure that 75 per cent cost certainty of construction was achieved before starting on site. Mace was appointed construction manager in October 1995. The tender returns for major elements of work were over the cost-plan allowance. The team decided to postpone the start on site to ensure cost certainty was achieved.

Value-engineering workshops with all parties were held, and by testing market trends significant savings were achieved without compromising the required quality and design intent. Although construction start was delayed to April 1996, the original completion date of June 1997 was achieved, and within budget. The costs are based on the original cost-plan allowance for construction and exclude design and projectmanagement fees, building-control costs and client's own furniture installation.

Specification notes (main building, link and lecture theatre)

SUBSTRUCTURE FOUNDATIONS/SLABS 450mm-diameter bored piles to main office structure. Pile caps and ground beams linking piles to superstructure.

Ground-floor slab cast on permanent formwork

SUPERSTRUCTURE FRAME Reinforced in-situ concrete frame, five storeys, incorporating fairfaced exposed finishes to walls, ceilings and columns UPPER FLOORS Wide-span reinforced-concrete flat slabs supported by integral beams. Reinforced-concrete shear walls formed the cores and entrance atrium, all with exposed fairfaced finish. The top floor used a structural-steel framework of columns, roof trusses, associated framework and bracing, prepared to receive a decorative finish

ROOF Incorporates profiled aluminium standing-seam sheet-mill finish, concealed reformed aluminium gutters to PVC-U syphonic rainwater system mounted on a structural-steel decking with mineral-fibre mat insulation. The flat-roof areas use a butyl-rubber polymer membrane upside-down construction finished with precast slabs and stone ballast

STAIRCASES Two reinforced in-situ concrete escape stairs, one concourse stairs and one atrium stairs, with powder-coated steel balustrades and handrails. Vinyl-covered treads to the escape stairs and preformed terrazzo treads to the atrium and concourse stairs. Two access and escape stairs are provided for the lecture theatre, all in reinforced in-situ concrete finished to accept directly applied vinyl treads.

EXTERNAL WALLS, WINDOWS, EXTERNAL DOORS Consists of extruded aluminium curtainwalling system with silver anodised and polyester finish. Low-E double-glazed units for fixed and opening lights, with white ceramic-backed glass for the fixed opaque spandrel panels. A zinc rainscreen system is used on the top floor supported by a secondary support system. The assemblies are pressure-equalised, drained and ventilated pressure plate framing systems fixed to and supported from the main concrete fame (restraint only from steelwork). Electronically controlled solar shading is used toge ther w ith a pass ive system a l l fixed to the ex terna l walkways. Aluminium anodised double-glazed windows electronically and manually operated on main elevation and clerestories. Aluminium anodised double-glazed doors on balconies, cores and concourses. Electrically powered sliding door to main entrance. Aluminium louvred doors to lift plant rooms

INTERNAL WALLS AND PARTITIONS Plasterboard drylining to office cubicles, meeting rooms and cores, hardwood glazed framing to entrance areas, shaftwall to lecture theatre lift, plasterboard and acoustic finish to lecture theatre, decorated fairfaced concrete to other areas

INTERNAL DOORS Ash-veneered flush doors to main entrance lecture theatre, atrium and service risers; flush glazed softwood doors to cellular offices to floors

INTERNAL FINISHES WALL FINISHES Emulsion to walls and concrete areas

FLOOR FINISHES Carpeted raised-access floor to office areas, carpeted solid floor to concourse/main entrance, lecture theatre, terrazzo tiling to cafeteria, Junckers flooring to stage, vinyl covering to WCs, kitchens and escape areas

CEILING FINISHES MFsuspended curved ceiling to top floor, MF suspended ceilings to cellular offices, concourse, cafeteria, lecture theatre stage, suspended tiled ceilings to kitchens and core areas, existing metal mesh ceiling to lecture theatre, painted soffits to remaining areas including main office

FITTINGS AND FURNISHINGS FURNITURE Hardwood veneered reception desk, proprietary office desks, chairs, screens, cabinets, cafeteria tables and chairs, folding fixed seating with writing tablets to lecture theatre

SERVICES SANITARY APPLIANCES Inset wash basins, ceramic WCs, urinals, cleaners' sinks, stainless-steel drainers

KITCHEN EQUIPMENT Stainless-steel dishwashers, fridges, sinks, trays, servery, freezers, coffee and tea makers, cookers

DISPOSAL INSTALLATIONS Cast-iron soil and vent gravity systems. Syphonic rainwater system

WATER INSTALLATIONS Extension of existing services within the campus

SPACE HEATING/AIR TREATMENT Natural ventilation via opening windows operated by BMS together with the existing MTHW pipework for heating.

Separate ventilation plant for the kitchens and use of modified existing plant for the lecture theatre ELECTRICAL SERVICES Mains and distribution switchgear, small power, automatic adjustable general lighting, proprietary luminaires to cores, lecture theatre and stage areas

LIFT AND CONVEYOR INSTALLATIONS Three hydraulic lifts

PROTECTIVE INSTALLATIONS Lightning-protection system

COMMUNICATION INSTALLATIONS Voice and data, fire alarm, security and building management system to control and monitor the various engineering systems

BUILDER'S WORK IN CONNECTION EXTERNAL WORKS LANDSCAPING, ANCILLARY BUILDINGS £223,330

Cost summary (main building and link only Cost per m Per cent (£) of total

SUBSTRUCTURE 54.99 6.27

SUPERSTRUCTURE Frame 65.52 7.47 Upper floors 58.09 6.63 Roof 62.47 7.13 Staircases 6.77 0.77 External walls, windows, 224.30 25.58 external doors Internal walls and partitions 26.13 2.98 Internal doors 17.52 2.00 Group element total 460.80 52.56

INTERNAL FINISHES Wall finishes 19.23 2.19 Floor finishes 51.87 5.92 Ceiling finishes 12.39 1.41 Group element total 83.49 9.52

FITTINGS AND FURNITURE 5.21 0.59

SERVICES Sanitary appliances 4.17 0.48 Disposal installations 2.80 0.32 Water installations 5.78 0.66 Space heating/air treatment 61.60 7.03 Electrical services 87.13 9.93 Lift & conveyor installations 13.26 1.51 Protective installations 1.49 0.17 Communication installations 46.55 5.31 Builder's work in connection 3.99 0.46 Group element total 226.77 25.87

PRELIMINARIES & INSURANCE 45.49 5.19 Total 876.75 100.00 Total construction cost analysis

MAIN BUILDING INCLUDING LINK £4,848,773

LECTURE THEATRE £500,741

EXTERNAL WORKS AND DRAINAGE £223,330 Total £5,572,844

CREDITS

CLIENT The Open University

ARCHITECT Feilden Clegg Architects: Peter Clegg, Keith Bradley, Andy Theobald, Tim Hall, Alan Wainer, Anne Claxton, Rob Gregory, Darren Cater

QUANTITY SURVEYOR AND CONSTRUCTION MANAGER Mace

STRUCTURAL ENGINEER Buro Happold: Tim Mander

SERVICES ENGINEER Buro Happold: Tony McLaughlin

CLADDING CONSULTANT Montresor Partnership: Harry Montresor

CONTRACTOR Mace LANDSCAPE Grant Associates

CONTRACT TYPE Construction Management

START DATE February 1996

COMPLETION DATE June 1997

TOTAL COST £5,572,844

TOTAL FLOOR AREA 6900m2

SUBCONTRACTORS AND SUPPLIERS piling Stent Foundations, sub and superstructure P C Harrington, curtainwalling installer MBM Fabri-Clad, hard floors Quilligotti, drylining West London Plastering , combined services T Clarke (Midlands), window cleaning equipment HCL, lifts Otis, WC fit-out H S Dev, render Renocon, roof finishes Allan Roofing, raised floors System Floor, office light fittings Trilux, WCcubicles Amwell, lecture theatre seating Cazzaro, temporary accommodation Alandale Construction, soft floor finishes Gordon Rose Associates, kitchen equipment Garners Catering Equipment, furniture & fixed seating SKS International, temporary electrics Wysepower, canteen HardHat Cafe, general metalwork Littlehampton Welding, roof structure SGI, roof finish Sika, curtain walling Schuco, render Sto, controls/BMS E Squared

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