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MODELLING CAN ENSURE THE DESIGN IS ON TRACK

TECHNICAL & PRACTICE

Sophisticated modelling techniques demand a good synergy between architect and engineer and between different engineering disciplines, as this case study of a Foster + Partners/Buro Happold collaboration shows.

The Thomas Deacon Academy in Peterborough, the largest of 47 academies completed to date, will amalgamate three existing secondary schools to house 2,200 students when it opens in September. Returning from a recent visit to Thomas Deacon, Ty Goddard, Director of the British Council for School Environments, described the school as spectacular. 'This is not all fiwowfl factor, ' says Goddard. 'It is a very visual environment which oozes respect for young people.' He also notes that the project is 'majorly ambitious, both educationally and technically.'

The academy's website says that 'it is important that the pupils never feel lost in their own Academy'. Foster + Partners, which has five academies under its belt and three more in the pipeline, tackled the size issue by creating six colleges within the school, which are expressed in architectural terms by amoeba-like pods. A triple-height central concourse provides visual orientation, doubling as circulation and breakout space.

The academy's specialisms - science and maths - will be highlighted on plasma screens in the concourse, but sports and performing arts also figure high in the curriculum. Classrooms, orientated north and south, are wrapped around a sinuous building perimeter to maximise natural light and ventilation. IT rooms, the theatre, the gym and the kitchen - spaces which do not require daylight - face east and west where an absence of windows means solar gain is not an issue. Thomas Deacon has received criticism in the broadsheets recently for its lack of playground, but Goddard says this misses the point entirely because there is plenty of recreational space on the site.

Thomas Deacon has proved a design challenge for both architect and engineer. 'The good thing about working for Foster, ' says Andy Nicholson of consultant engineer Buro Happold, 'is that they push their consultants quite hard. The design of the central concourse and its curvy roof required good synergies between [engineering] specialisms, especially people movement, fire, services and acoustics, ' adds Nicholson.

People movement simulation has its origins in fire egress.

At Thomas Deacon, it has been used to understand the ow of students through the school and to identify counterows and blockages - potential hotspots for bullying. Darron Haylock of Foster + Partners says this simulation assisted the client in achieving value for money because the school didn't want to use fire-escape stairs for vertical circulation and needed to optimise the number and configuration of the stairs. Haylock finds people movement simulation an extremely useful tool which the practice has gone on to use in other projects.

As a baseline for the simulation, Buro Happold collected real data on student movement at the existing Thomas Deacon school, rather than working from guidance documents. Peak times proved to be lunch, morning arrival and afternoon departure. The resultant design changes included adding bridges, adjusting the width of stairs, and widening and relocating doors. 'Models are just tools to give you confidence that the design is moving in the right direction, ' says Nicholson. Computer modelling may increase confidence, but one can argue that it has resulted in a deskilling of the architect, who has become increasingly dependent on a wide range of consultants to crunch numbers and interpret results.

Fire engineering was also critical at Thomas Deacon, particularly because arson is a major source of fire in schools.

According to the Arson Prevention Bureau, an average of 20 schools a week have a major fire. Proactive fire prevention measures include: a laser beam which runs the full perimeter of the school and is linked to a remote monitoring system; and locking refuse, a potential fire starter, in stores 15m away from the building.

A good interface between fire and security design, undertaken by Faber Maunsell, avoided the use of redundant fire-safety systems.

The fire strategy was developed by looking at the impact of particular fies on the life safety of the occupants and the building. Potential fire locations were agreed with the client and Building Control, in order to work out worst-case scenarios. These were then analysed with CFD modelling to determine the size and location of roof vents necessary to keep smoke 2m above the oor at secondfloor level to ensure safe evacuation. The people movement modelling was used in emergency mode, rather than using a separate evacuation model. A final aspect of fire prevention is what Buro Happold calls the 'circle of safety' - fire maintenance procedures. A report on fire safety sets out operational management and checklists for use by the academy.

An important engineering overlap between fire and services looked at the natural convective currents in the concourse to understand the stack effect. Environmental engineering also helped establish optimal classroom depth by studying natural ventilation, concluding that a classroom could be a maximum of 2.5 times its height to maintain indoor air quality. Night cooling is achieved by locating high-level windows close to ceilings and all concrete ceiling soffits are exposed to increase thermal mass.

One of the more complex aspects of the design is a 3D roof - rapidly becoming a Foster trademark - which incorporates structure, acoustic attenuation, roof vents and lighting. In a first for Fosters + Partners, mirrors were integrated into the curvature of the roof to illuminate landlocked spaces. Projector lights from below are directed on to the mirrors and reected back into the rooms below.

Buro Happold has also used post-occupancy evaluation of previous academies to inform design at Thomas Deacon. Easy energy savings are being made by ensuring that lights and equipment are switched off out of hours. Lighting controls have been modified so that security lighting, which represents only about 10 per cent of all lighting, is clearly labelled and can be switched on and off separately.

A critical assessment of the Thomas Deacon Academy will only be possible when the school opens its doors in September.

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