In May a distinctive new swingbridge spanning the ManchesterShip Canal will be completed, aspart of the ongoing regenerationof the city’s redundant docklands.

Media City Footbridge willexpand the Media City UK devel-opment — which includes theBBC’s northern headquarters —south to Trafford Quays. The £11million bridge will improve pedes-trian connections around SalfordQuays, forming a circular route viathe existing Lowry Bridge to theLowry Centre and the ImperialWar Museum North.

Beyond its functional role, abridge has symbolic significance asa gateway, a creator of connectionsand as a place in itself. Designedby Wilkinson Eyre and engineeredby Gifford, the footbridge has anelegant silhouette with eight taper-

ing steel masts that rise above aslender, arching deck. Architectureand engineering have been inte-grated in a structure that is expres-sive and contextual. Steelwork is byRowecord Engineering.

The bridge curves in plan in aradius centred on the drum of theLowry Centre, a pattern set out inthe masterplan to give a focus andcoherence to future developments.

“It’s incredibly efficient.Because the whole bridge is on a

curve the centre of gravity is on theedge of the deck, which means youcan support the deck on one sideonly,” says Wilkinson Eyre associ-ate James Marks.

The deck is supported by a seriesof stay cables that transfer the loadover the steel masts and back downto a wider deck behind that acts asa counterweight. The whole struc-ture can rotate about a pivot belowthe masts to allow ships to pass.

When it was completed in 1894the Ship Canal was the largest navigation canal in the world.Although closed to commercialtraffic since 1982, a public right ofnavigation still exists and closingit off with a fixed bridge wouldhave prevented a potentially valu-able asset being used in the future.

In its closed position the clear-ance is the same as that beneath theLowry Bridge. The biggest designchallenge was achieving the nec-essary height without the gradientbecoming too steep or the accessramps too long.

The Highways Agency designcriteria demand a maximum gra-dient of 1:20 for a footbridge butsuch a shallow slope would resultin the approach ramps extendingdeep into the development site onthe north side, impeding pedestri-ans using the canalside walkway. Itwas agreed that the navigationenvelope could be relaxed slightly,and that a 1:15 gradient would beacceptable. At the north abutmentthe ramp is only 1.25m above thecanalside walkway, maintainingvisual continuity.

PROJECT TEAMClient Peel HoldingsArchitect Wilkinson Eyre ArchitectsStructural engineer GiffordMechanical engineer Atkins BennettLighting designer PinnigerPlanning consultant S Wright LtdConstruction management BovisMain contractorBalfour Beatty Civil Engineering LtdSteelwork contractorRowecord Engineering

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Cable technology gets Salford in the swing

A new footbridge designed by Wilkinson Eyre Architects over the Manchester Ship Canal at Salford uses steel to create a structure that is both functional and visually appealing Text by Graham Bizley

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Bridge plan1 Inclined stainless-steel

parapet system at concave western edge of stepped approach to bridge at south abutment.

2 Stainless-steel pedestrian barrier housing.

3 Stainless-steel barrier and control pendant housing.

4 Approach ramp:Cantilevered glass balustrade system system.Stainless-steel guardrail anddemountable framed stain- less-steel wedgewire panel.

5 Stainless-steel and glass parapet system with integral lightbox.

6 Fabricated stainless-steel

and timber bench and anchorage assembly.

7 Plant room access hatch assembly.

8 Framed aluminium decking system to western edge of bridge deck.

9 Stainless-steel and glass parapet system with integral lightbox to eastern edge of bridge deck.

10 Inclined stainless-steel parapet system to convex western edge of bridge deck from gridline 52 to the northern end of the bridge.

11 Stainless-steel pedestrian barrier housing at north abutment.

CABLE-STAYED BRIDGE STEEL DECK STRUCTURE

The deck is an orthotropicsteel box, which means thatthe structural top plateforms the actual surface ofthe bridge, with stiffeningplates beneath to transferthe loads back to theprimary structure.

An orthotropic steel deckis considerably lighter thanan equivalent concrete

OPENING MECHANISM

The steel pivot mechanism rotates on a 4m slew ring.

Concealed beneath thepedestrian deck is the pivotmechanism on which thebridge rotates.

A 13m-diameter reinforcedconcrete caisson foundationrests on bedrock 11m belowwater level. Above thewaterline the visible sectionhas a diameter of 7.3m.

The mechanism itself issteel, consisting of a femaleshoe cast into the concretebase and a cast male pin thatrotates within it.

The pin is welded into thedeck structure and to themast base above. Threehydraulic rams fixedhorizontally beneath thedeck rotate the structure.

The pin rotates on a 4m-diameter slew ring whichconsists of two precision-made steel rings separatedby a captive channel of ballbearings, similar to thoseused in tower cranes.

The slew ring absorbs allaxial and radial forces andthe resulting tiltingmoments.

Initially the design teamtried a different approachbecause the lead-in time ofone year for a slew ring was

too long. When the economicdownturn started, however,lead-in times reduced so thatthe manufacturers were ableto supply the bearings withinprogramme.

Media City Footbridge is anasymmetric cable-stayed swingbridge with a 65m main span. Acable-stayed design minimisesthe thickness of the deck andmaximises clearance beneath.

The bridge was fabricated onland adjacent to the canal, fromsections brought to site by roadon low-loaders.

“Modeling the geometry wasa major challenge and then wehad to break it down intomanageable loads that could betransported and weldedtogether on site,” says GarethSummerhayes, contractmanager at RowecordEngineering.

To avoid the health andsafety risks of working overwater, as much work aspossible was done on landbefore the entire structure wasslid across on rollers anddropped on to its permanentconcrete support in the canal.

At its narrowest the deck is4m wide, flaring out to form a16m-wide public space at thesouth end that counterbalancesthe weight of the main span.

Eight high-tensile spiral strandsteel cables are attached to theconcave eastern edge of thedeck. These are parallel but areset out tangential to the curveso the support plane warps inthe air, forming a dramaticsculptural canopy overhead.

Each cable is tied to its ownsteel compression mast thattransfers the load down throughthe deck to the main supportbeneath the bridge. The mastsare tied together at their tips tokeep them in alignment.

At the bottom, each mastrests on a stainless-steel balland socket joint that expressesthe transfer of point load downinto a welded steel base.

Uplighters are housed in bolt-on stainless-steel sheaths.

At the south abutment,pedestrians pass through agateway formed by the eightcable-stay anchorages. Abench cantilevered from eachanchorage prevents peoplewalking into the cables andencourages gathering in thespace beneath the cables.

The tapered shape of themasts was made by cuttingout a section from a standardCHS steel tube and welding itback together so the resultingsection is eye-shaped ratherthan circular at the ends.

Live loads on the structurewill vary with pedestriannumbers and wind uplift. The bridge therefore has tomaintain an equilibrium toensure the cables alwaysremain in tension.

In its closed position thenose and tail of the bridgeengage with the abutments toprovide support and limitdeflection. The deck is liftedoff these supports by a jackingmechanism when it opens.

structure — an importantfactor for a swing bridge —and it allows the deck to bevery thin, which helps reducethe gradient of the approachramps. The deck surface isfinished with a non-slip epoxyaggregate.

The box is trapezoidal insection, its faces angled toaccentuate the form of theMast bases rest on steel joints.

Eight steel maststransfer the loadfrom the cables tothe main support.

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bridge and reduce its visualweight. Rather than bringingthe plates to a point with anawkward weld, the leadingconcave edge is made from aCHS tube that blurs thetransition from top surface tosoffit.

On top the box has a verticalface that incorporates alightbox to illuminate the

walkway. On the western edgethe deck surface changes toperforated aluminium throughwhich the water can be seenbelow.

The aluminium decking sits on transverse steel beams cantilevered off themain box beam, expressing the relative thinness of thewestern side.

Deck detail

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1 Footbridge2 Media City3 Trafford Wharf

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The deck opening mechanismsits on foundations 11mbelow water level.

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STEEL FOCUS: MEDIA CITY FOOTBRIDGE In association withThe British Constructional Steelwork Association and Tata Steel

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1 Continuous perforated, non-slip aluminium decking system. Nominal width 1.5m

2 High tensile, spiral strand steel stay cable

3 Inclined stainless-steel parapet system to western edge of bridge deck

4 Shaped fabricated box defines deck edge and provides support for parapet system

5 Demountable, framed stainless-steel

wedgewire panel system at floor level to western edge of brick deck

6 Fabricated steel deck box

7 Stainless-steel and glass parapet system with integral lightbox to eastern edge of bridge deck

8 Non-slip epoxy aggregate surface finish in silver-grey

9 Continuous stainless-steel guardrail at low level

Elevation1 Stainless-steel parapet

with integral glass lightbox system to eastern edgeof approach ramp at south abutment

2 Inclined tapering painted mild steel mast arrangement

3 Shaped concrete pier and pile cap

4 High tensile spiral strand

steel stay cable5 Shaped fabricated box

defines deck edge and provides support for parapet system

6 Stainless steel parapet with integral glass lightbox system to eastern edge of bridge deck

7 Existing quayside structure8 Ramp to Media City

The steelconstructionmeans thedeck can bevery thin.

After a three-year constructionprogramme, the Royal Shake-speare Company’s reworked the-atre complex in Stratford-upon-Avon was officially opened lastmonth and stage productions havebegun in the main auditorium.

This was the most complex spacein the entire project, and the last tobe completed. One of the prioritiesof Bennetts Associates’ design wasto create a greater intimacybetween the 1,040-strong audienceand the actors by halving the max-imum distance from seat to stage.This was achieved with a thruststage and also through the use of asteel structure that plays both afunctional and aesthetic role in thedesign of the auditorium.

Steel was a natural choice for theframework because it allowed aslimmer structure than concrete orwood. This assists sightlines andhelps the architects to bring theaudience closer to the stage.

Bennetts was also keen to take adifferent approach in the mainauditorium to the timber structureof the far smaller Swan Theatre atthe RSC. Instead, a “scaffold” ofexposed architectural steelworkcolumns and beams was used to

support faceted balconies of seat-ing around the auditorium. Abovethis are two further steel structuresunseen by the audience: three lev-els of lightweight technical bridgessuspended from giant roof trusseswhich span over the new flytowerand rest on the concrete frame ofthe building.

“Steel achieves a delicacy of con-struction. Every millimetre countsin this space — it really does makea difference. The slimmest con-struction is absolutely essential,”says Bennetts Associates directorSimon Erridge.

The emphasis was on as light-weight a steel construction as pos-sible in order to minimise the loadand piling requirements, especially

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STEEL FOCUS: RST AUDITORIUM

A versatile steel structure was atthe heart of Bennetts Associates’Royal Shakespeare Theatre Text by Pamela Buxton

Taking thelead role inStratford’srevival

Four 24m-long steel trussescriss-cross the top of thespace, resting on the concretewalls that form the sides of theauditorium. Weighing 20tonnes each, these trussessupport both the uppertechnical levels which aresuspended from them plus 30hoists for flying sets weighingup to a total of 25 tonnes.

They have to be stiff enoughto keep deflections to aminimum in order to becapable of lowering scenerytravelling at a rate of 2.5m persecond with the utmostprecision. The trusses are 3.4mdeep, allowing technicians towalk through them as theywork above the auditorium.

By modelling the effect of a

fire on stage, Buro Happoldwas able to show that thetrusses and other technicalsteelwork did not need a fireprotective coating — whichwould have been problematicgiven that they are constantlyhandled and clamped when inuse. In this way the need for asafety curtain between theproscenium and thrust stage

was avoided. Large smokeextract fans are installed in the roof.

The original flytower hasbeen refurbished and the oldconcrete roof replaced with alighter weight steel and timberroof. This allows more of thestructural load capacity to begiven to supporting theatreservices.

The auditorium seating isarranged on three levelsaround a 7.2m-wide, 10.25m-deep thrust stagethat protrudes from theproscenium. The stallsseating rests on a concreteslab supported on a steelsub-frame.

Ten exposed cruciformcolumns support the light-weight steel structure thatholds the circle and uppercircle seating. The ring beamstructure is fixed back toconcrete cores behind thetimber-clad walls of theauditorium.

The slender columnsmeasure 10m high, including1m concealed belowauditorium floor level, andare set approximately 4.5mapart, breaking up the largeaudience into small pocketsof approximately 30 seats. In all, there are 24 types ofseats, including five widthvariants from 450-555cm.The steel structure is leftexposed, including the ribs ofthe underside of the circlebalconies, which have paintedplywood soffits.

To ensure the columnsaren’t too prominent anddon’t interfere with sightlines,they are positioned one rowback from the front of the

balcony and this front row isbolted on to the structure andcantilevered out.

An extra stipulation wasthat the two seating baysclosest to the prosceniumhad to be demountable atcircle, upper circle andtechnical area level to giveproduction designers theflexibility to use large piecesof scenery near theproscenium. These wedge-shaped blocks can beunbolted from the rest of thestructure if required.

In all, more than 500components weremanufactured for theauditorium, according to PaulTierney, associate director ofCMF, the steelworkcontractor responsible for theexposed steelwork in theauditorium, which had a teamof more than 40 working onthe job. All welding was doneoff site, thus limiting the timespent constructing thestructure in the auditoriumwhere it was bolted together.

One of the biggestchallenges was incorporatingall the ventilation, fire, IT andelectrical servicing within theslim auditorium, especiallythe need to bring large amountsof cabling to lighting bars atthe front of the balconies.

Steel beams fan out from the concrete walls.

Cutaway section showing steel construction

Ground floor plan

in a difficult waterside location. Intotal, the auditorium containsapproximately 650 tonnes of steel.

Overall, the theatre complex isexpected to have a 20% smallercarbon footprint than the originaltheatre, assisted by the use of cross-laminated timber floor panelsinstead of precast concrete.

Although the auditorium hasbeen designed as a permanentstructure, the steel structure couldbe dismantled to allow the wholespace to be reconfigured.

“It’s a steel armature that can bechanged, and the expression ofthe steel elements supports that,”says Erridge. “If you really wantedto, you could unbolt it in 30 years’time and redo the auditorium.”

PROJECT TEAMArchitect Bennetts AssociatesEngineer and transport consultant Buro HappoldTheatre consultant Charcoalblue Construction management MaceAcoustic consultant Acoustic DimensionsProject management & strategicplanning Drivers Jonas DeloitteQS and planning supervisorGardiner & TheobaldSteelwork contractors BillingtonStructures (primary steelwork); CMF (auditorium steelwork)

The architect’s initial instinctwas to paint the exposedauditorium steelwork, or toshot-blast it. Eventually, it wasdecided to leave it untreated,except for a clear lacquer topreserve the finish.

CMF similarly left the raisedwelding on the auditoriumstructure intact rather thangrinding it off, as would be moreusual, putting more pressure onthe welders to make sure theirwelds all matched and lined upperfectly.

“Not to clean up the weldsgoes against the grain,” saysCMF’s Paul Tierney. “We had torelay a few welds where theguys had naturally clearedthem up.”

Project architect AlasdairMcKenzie adds: “You get asense of it being handmadeand that’s deliberate. All thecolumns are very different —some are orangey, some blue.”

This ties in with the broaderdesign decision to have rawermaterial finishes in theauditorium — rough sawnoak timber panels are visibleon the rear walls andexposed brick around theproscenium — in contrastwith the more highlyfinished foyer areas.

AUDITORIUM STRUCTURE ROOF TRUSSES

UNTREATED STEELWORK

1 Stage and flytower2 Existing 1930s

flytower basement3 New thrust stage basement4 New lightweight roof to

1930s flytower5 Auditorium balcony

structure6 Suspended technical

lighting level7 Removable auditorium

balcony sections8 Primary roof trusses

9 Auditorium air handling units

10 New foyer canopy roof11 New restaurant hung

from roof12 Concrete stability walls and

auditorium access ramps13 New steel prop to enable

existing basement wall opening to be cut

14 Existing Swan Theatre15 New basement plant rooms16 Existing art deco foyer

1 Royal Shakespeare Theatre2 Swan Theatre3 Stage and wing spaces4 Colonnade5 Foyer void6 Scott foyer

7 Fountain staircase8 Café9 Theatre tower10 Library and

reading room11 Stage door

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Above: Aerial view ofthe theatre’sconstruction.

Right: Theslim steelstructure isbothaestheticallyappealing andallows theaudience tosit closer tothe stage.

Steelwork in the auditorium was left untreated for a raw finish.

Mock-up ofauditoriumsteelworkshowingexposedwelds.

Thelightweightsteelstructurethat holdsthe circleand upperseating issupportedby 10m highcolumns.

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STEEL FOCUS: TARGET ZERO

Rated Breeam Excellent, SheppardRobson’s One Kingdom Streetoffices for Development Securitieswas one of the first UK officeschemes to incorporate carbon foot-printing of the construction processthroughout the supply chain.

Completed in 2008, the24,000sq m building provides typical floor plates of 2,500sq mwith floor-to-ceiling glazing on all facades. Accommodation isarranged over 10 storeys andaround two central atriums. It hasa 12m x 10.5m steel grid compris-ing fabricated cellular steel beamssupporting a lightweight concreteslab on a profiled steel deck. The£65 million building sits on apodium over the route for Cross-rail and steel was the only structureable to span the gaps between thebeams in the substructure.

Carbon reduction was consid-ered from the onset of the project’sdesign, right from the orientationof the building through to thefacade design and the specificationof the building systems.

“The design originally had alarge atrium on the north but wechanged it to the south because itoffered a better buffer to solargain,” says Sheppard Robson part-

ner Mark Kowal.The main vertical escape and

service cores are at the east andwest ends to minimise sun pene-tration. On the south side, themain circulation core and atriumact as a buffer between the exter-nal environment and occupiedfloors. Offices that do engage withthe south facade are protected byexternal horizontal deep louvres.

The building achieved itsBreeam Excellent rating with thehelp of geothermal piles to provideground source cooling and the useof renewable energies such as solarroof panels. An active chilled beam

air-conditioning system was con-sidered but at the time this wasn’twidely accepted by clients andinvestors and so was not used.However, perceptions of this tech-nology are now changing.

“The ethos of One KingdomStreet is about trying to reduce car-bon in the whole delivery process.It’s not just about sticking in clevergizmos,” says Neil Burns, directorof operations in Europe at Aecom.“It has done well to optimise thebalance between lighting levelsand energy consumption.”

Kowal has noticed an increasein emphasis on low-carbon design

since the creation of One KingdomStreet. “It’s genuinely being drivenright through the design process,even by the clients,” he says.

Burns adds that it is importantthe quality of the environmentisn’t neglected. “It’s no use havinga low-carbon solution that no onewants to occupy,” he says.

What the Target Zero reportsays: The Target Zero report ison an amended version of thebuilding stripped back to just satisfy the requirements of2006 Part L. Measures are then re-added and measured for effi-

ciency and cost. A package of the most cost

effective energy efficiency meas-ures costs 0.3% and yields a 42%saving in regulated emissions,which well exceeds 2010 Part Lrequirements. To achieve BreeamOutstanding would require 9.8%more capital cost compared with0.2% and 0.8% respectively forVery Good and Excellent.

Lighting accounted for 27% ofcarbon emissions. The impact ofthe structure on operational emis-sions was small — varying 0.5%between post-tensioned concreteand a steel frame composite.

New research will help architects maximise low-carbon design

ARCHITECTFAIRHURSTS DESIGN GROUPSTRUCTURAL ENGINEERJACOBSBUILDING SERVICES CONSULTANT AECOM

Completed in late 2010 for clientPeel Holdings, the Holiday Innbuilding is attached to the mainstudio building in the Media CityUK complex in Salford. Chosen asthe mixed-use case study in theTarget Zero guidance, this northblock consists of two levels of hotelreception facilities, plus five floorsof studio offices and eight floors ofhotel rooms above that.

The entire building is ratedBreeam Very Good, assisted by theTrigen Combined Heat & Powersystem that provides heating, cool-ing and hot water for the whole ofthe complex.

Architect Fairhursts had to

contend with changing uses — thesouth tower was initially residen-tial before changing to office use,and in the north tower, Fairhurstsis looking at fitting out the officefloors as hotel bedroom floors.

Building services consultantAecom looked initially at passivemethods of reducing energy needssuch as beefing up the thermalperformance of the build-ing fabric and glazingsystems that went intoit. But Aecom concludedthat utilising heat recoveryand CHP systems was farmore effective, especially ona site with diverse uses.

“With building regulationsgetting tighter anyway, extrainvestment in the fabric was-n’t giving the same measure ofreduction as something moreactive,” says Graham Millard,regional director of Aecom.

“If you had a single use build-ing, increasing its thermal fabricrequirements might have beenmore effective. The more diversethe uses, the more advantageousCHP is.”

Energy use in the hotel isreduced by occupation-sensitivelighting and air-conditioning tech-nology. Unlike the other buildingson the site, the mixed-use block didnot achieve Breeam Excellent.

“There’s not a lot you can do with

What is Target Zero?

ONE KINGDOMSTREETPADDINGTONCENTRAL, LONDON

HOLIDAY INN MEDIA CITY UK, SALFORD

Target Zero guidance on achievinglow-carbon buildings has beenlaunched by the BCSA and TataSteel. Here are three steel-framedprojects featured in the research Text by Pamela Buxton

SCHOOLSThis first Target Zeroreport was based onChrist the King Centrefor Learning inKnowsley, Liverpool,built by Balfour Beattyand opened in January2009. Occupied by 900pupils and 50 staff the9,637sq m steel-framedbuilding is based on a9m x 9m structural gridand requiresmechanical ventilation.

WAREHOUSESThis study is based onthe 34,000sq m DC3warehouse at ProLogisPark, Stoke, which wascompleted inDecember 2007. Thereport was writtenbefore the governmentintroduced its feed-intariffs for renewableenergy sources in April2010. A revised reportwill be publishedshortly.

SUPERMARKETSThe supermarketreport is based onAsda’s food store atStockton-on-Tees inCleveland,completed in May2008. The buildinghas a floor area of9,393sq m over twolevels. The retailfloor area, includinga 1,910sq mmezzanine level, is5,731sq m.

Target Zero is a £1 million research programmeset up to provide free guidance on the design and construction of sustainable, low- and zero-

carbon buildings in the UK. It is funded by Tata Steel andthe British ConstructionalSteelwork Association(BCSA) and has been carried

out by a consortium of sustainable constructionorganisations including AECOM and Cyril Sweett.

The guidance analyses five non-domesticbuilding types — a school (Christ the King Centrefor Learning, Knowsley), a distribution warehouse (DC3, Prologis Park, Stoke), a supermarket (ASDA food store, Stockton-on-Tees), a medium-to-high-rise office (One Kingdom Street,Paddington) and a mixed-use building (HolidayInn, Salford Quays).

In each case, the designs are modified to a base level compliant with 2006 Part L beforeintroducing the latest Building Regulationchanges.

The research focuses on how Very Good,Excellent and Outstanding Breeam ratings can beachieved and at what cost; quantification of theembodied carbon in buildings with differentstructural forms; and how operational carbon canbe reduced by incorporating energy-efficiencymeasures and low- and zero-carbon technologies. Want to know more?The first three guidance reports — Schools,Warehouses and Supermarkets — can bedownloaded now from the Target Zero websitewith the final two — Offices and Mixed-Use — to follow soon. www.targetzero.info

One Kingdom Street is designed around two central atriums, which help reduce solar gain.

Long section

Ground floor plan

1 Hotel 2 Production offices3 Studios4 Philharmonic5 Audio studio6 Media Enterprise Centre offices7 Speculative offices

CHRIST THE KING CENTRE FOR LEARNING KNOWSLEY, LIVERPOOLARCHITECT AEDASSTRUCTURAL ENGINEER /M&E ENGINEER AECOM

Balancing educational needs withenvironmental performance was akey challenge for architect Aedas inits design for Christ the King Cen-tre, one of seven BSF schoolsdesigned by the firm in Knowsley.

Completed in 2008, the 9,637sqm building accommodates 900students, although it is now threat-ened with closure owing to fallingpupil numbers. It is based on a 9mx 9m structural grid and has aBreeam Very Good rating.

One of the biggest issues was theclient’s stipulation for 80sq mclassrooms grouped around a cen-tralised learning zone for each keystage. This led to a deep plan for thethree-storey building, with KeyStage 3 accommodated on the topfloor, Key Stage 4 on the middle,and specialist-teaching accommo-dation on the ground floor.

Unfortunately, says Aedas asso-ciate director Rob Hopkins, environment and educational pri-orities were “almost at oppositeends of the spectrum”.

“As soon as you have a schoolwhere classes are deeper than7.5m, being able to use natural ven-tilation and daylight becomes chal-lenging,” he says. “So we developeda ‘Swiss cheese’ concept where we

carved holes into the building thatswept down so you could naturallyventilate.” He adds that M&Eengineers in the end went formechanical ventilation after it wasdecided to use a steel frame ratherthan post-tensioned concrete.

Very low sill levels in class-rooms made the most of the day-light. “Wherever you were, youhad a nice view,” says Hopkins.

Where the school did score wellin carbon reduction was the use of ground source heat pumps and heat-recovery technologiesinstalled by Balfour Beatty acrossall the Knowsley BSF schools.“That really helped us to reduce thecarbon footprint,” he says.

In the years since the KnowsleyBSF, low-carbon has become a

higher priority in Aedas’s schooldesigns, which now gain Excellentor Outstanding Breeam ratings.

“Knowledge is improving veryquickly,” says Hopkins. “In 2007,[low-carbon] conversations rarelytook place unless it was a specifi-cally low-carbon school design.Now, these conversations takeplace on every school we design.”

Hopkins welcomes new guid-ance on designing low-carbonbuildings: “Any information that iseasy to digest is vital, as is beingable to look at a number of differ-ent sources for that information.”

What the Target Zero reportsays: For a version of the schoolstripped back to “typical practice”(e.g. just compliant with 2006Regs etc.), the capital cost upliftneeded to achieve Breeam VeryGood was 0.2% compared with0.7% for Excellent and 5.8% forOutstanding.

Cancelling out regulated carbonemissions with on-site low carbontechnologies would cost 12%more. The guidance found a sig-nificant proportion of embodiedcarbon was in the substructure,and that the best results wereobtained using steel piles. Thestructure had virtually no impacton operational carbon emissions— with less than 1% variationbetween steel and concrete.

Aedas developed a“Swiss cheese” conceptfor this BSF school, bycarving ventilation holesin the structure.

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Plan strategy

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studios — they use a lot of energy.It’s the nature of the beast. It’s noteasy to achieve any more than VeryGood,” adds Fairhursts associatedirector Trevor Cousins.

He says architects and clients arestill learning about how to achievelow-carbon buildings. “Clientswant Breeam Excellent but theydon’t realise what we have to do to

achieve that.”Target Zero guidance

helps bridge this gap bypresenting fully costedguidance on differentmeasures that can beemployed to reduce car-bon and increaseBreeam ratings.

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The three-storey atrium.