Associated Architects’ boathouse for The King’s School, Worcesterm

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From the sustainability editor

Supported by the AJ, Open-City’s third annual Green Sky Thinking week will take place 15-19 April. This event stands out because it builds on what Open-City does best:

connecting the professionals who are driving innovation with those who can influence change.

Some 50 events will offer opportunities for focused interaction with industry leaders who are pioneering ways to make London a greener and more livable city.

Gardiner & Theobald’s Richard Francis, who hosted last year’s launch event, said: ‘Green Sky Thinking […] brought industry and government leaders to our door and opened up new discussions and opportunities for our business across the board.’ The Green Sky Thinking seminars are equally useful to anyone working at the forefront of sustainability as well as those in early stages of developing greener ways of working.

The AJ will host its own Green Sky session together with Feilden Clegg Bradley Studios. We will brainstorm ways to address the building performance gap. Though much discussed, the disconnect between how buildings are designed and how they perform remains poorly understood and is often perceived as someone else’s affair (AJ 28.02.13). But change is afoot. The combination of the Technology Strategy Board funding, the adoption of the Government Soft Landings (a commissioning and building aftercare protocol which will be mandatory from 2016) and the upcoming relaunch of the CarbonBuzz platform mean that an increasing pool of industry professionals – architects included – are gaining expertise in this area. This is no longer simply the domain of the Usable Buildings Trust and BSRIA who have pioneered work in this area for many years. We all have a duty of care.

This month’s Footprint feature – Associated Architects’ boathouse for an independent day school in Worcester – may at first glance be surprising. Beautiful and fit for purpose, this is an exemplary project with a thoroughly considered environmental agenda. Read closely and study the working detail.

Green Sky Thinking Week will take place in various venues across the capital from 15-19 April. For details go to: greenskythinking.org.uk

Open-City’s Green Sky Thinking week (April 15-19) will target both experts and novices, says Hattie Hartman

Diameter of smoke rings to be released from BIG’s Amagerforbraending waste-to-energy plant each time a quarter ton of CO2 is emitted

25m

Green Deal assessments since the 28 January launch

Annual CO2 emissions from Associated Architects’ boathouse (above) at King’s School, Worcester

Raised on Kickstarter to build an aquaponic farm on a London car park

1,803

9.01 kg/m2

£15,000+People without access to clean water(March 22 was World Water Day)

783 million

Associated Architects’ boathouse at The King’s School, Worcester, does not flout its robust environmental credentials, says Hattie Hartman Photography by Martine Hamilton Knight

Out onto the water

Footprint feature

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1. Creighton Memorial Gardens

2. Diglis Hotel3. Kings St Alban’s

Junior School

he fi rst boathouse at � e King’s School, Worcester was a barge purchased in 1914 for £18.

� ree boathouses later, an elegant prow-shaped building by Associated Architects has replaced a 1950s structure on the same site designed by the then master in charge of rowing. Every aspect of the new Michael Baker Boathouse (after an alumni donor) – from its careful siting to the fl ood-resistant design of the boat store to the meticulous selection of materials – has been lavished with attention to magnifi cent eff ect with a vigilant eye to sustainability throughout.

� e King’s School, Worcester occupies an organic accretion of buildings which front the southern fl ank of Worcester Cathedral. � e boathouse is Associated Architects’ eighth major intervention at the school over 14 years. Projects include: two 10-year masterplans, a library, and a new sports and performing arts centre, currently on site and due to complete in 2014. � e architects’ intimate knowledge of the school and its heritage context is made manifest in the boathouse.

� e site is exceptional. Approached through a 2.6m-wide lane which defi nes the school’s southern boundary, the boathouse sits roughly perpendicular to the Severn River. � e cantilevering fi rst fl oor forms a prow over the embankment, with its parade of handsome horse chestnuts and views of Worcester’s twin landmarks: the cathedral tower and Glover’s Needle, a reminder of the city’s glove-making past.

� e brief for the building was simple: a boat store with a multipurpose room above which could accommodate training for rowers as well as school and community receptions. � e goal was to create a facility where every King’s pupil would have an opportunity to learn the rudiments of the sport.

Project architect John Christophers brought a strong environmental agenda to the project, having Site plan

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Left An airtight sweet chestnut-clad training and reception area protrudes over the fl ood-proof brick boat store

completed Code Level 6/Passivhaus EcoVicarages for the diocese of Worcester (AJ Specifi cation 02.13) and Cobton House, also on the banks of the River Severn, which won an RIBA sustainability award in 2005.

� is modest building of just 772m2 does what all good buildings should – it makes sense of its surroundings.

By locating an entrance to the upper fl oor on the axis of Glover’s Needle in the adjacent Creighton Memorial Gardens, the practice has created an approach route through this previously under-utilised part of the school grounds and simultaneously provided wheelchair-friendly access to the building. Its cantilevered prow serves as a landmark on the embankment, anchoring the south-west corner of the campus. � e planners were receptive to what Christophers calls ‘a jewel-like modern incident along the embankment.’

� e jewel reference is accurate. On the sunny day I visited, the diagonal-laid sweet chestnut cladding shimmered. � e 32mm by 25mm chestnut laths of the rainscreen cladding are laid on a 15° angle, ‘like a bias cut dress,’ explains Christophers. � e timber prow of the upper fl oor sits over a brick base which houses the boat store, with a fl awlessly crafted ‘belly’ over the door fronting the river. � e building’s gentle curve echoes the site boundary which is also Worcester’s Bronze Age fortifi cation line. A rustic brick, chosen to marry >>

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Michael Baker Boathouse, The King’s School, WorcesterAssociated Architects

1. Ramp 2. Boat store 3. Mezzanine level

storage with dinghys underneath

4. Lobby 5. Workshop/office 6. Boiler, water tank,

solar store, wood pellets

7. Store 8. Severn Street 9. Riverside walk10. Glass prow11. Weights room12. Servery13. Kitchen14. WC15. Changing room16. Cleaner’s store17. Garden

maintenance area18. Terrace19. Creighton

Memorial Gardens

with existing Victorian bricks and the local sandstone, is laid in English garden wall bond – three courses of double length stretchers and one course of headers - providing just enough texture to compliment the diagonal siding above.

A handsome timber door from the narrow lane opens onto a dramatic top-lit ice birch-lined stair. On the right, an interior window offers a glimpse into the boat store – which has double the capacity of the old building and is the building’s raison d’être. Christophers refers to the store as ‘sacrificial’: it’s uninsulated, outside the airtightness line and designed to flood. Since the boathouse was occupied last April, the Severn has flooded four times, bringing more than a foot of water into the boathouse without damage.

The immaculate detailing and sensitive choice of materials continues inside. A welcoming maple stair, with 450mm going and 150mm risers, is a marvel, each step carefully aligned with the brick coursing and the beech panelling on either side. Above, a bespoke run of flush rooflights follows the line of the curved wall in an alternating A BB A rhythm, creating a play of shadows on the wall. Motorised for ease of operation, the rooflights open to enable natural ventilation during training, while deep coffers eliminate glare. Triple-glazed windows

Lower ground floor plan Upper ground floor plan

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and sliding doors open to the north overlooking the gardens and cathedral.

The boathouse’s exemplary environmental agenda is simultaneously robust and imperceptible, an approach more practices should adopt. Because the programme required a multipurpose space for training, teaching and receptions, a lightweight responsive building was needed.

Paramount attention was paid to insulation and airtightness with all electrics located in the floor to eliminate penetrations of the airtightness barrier. The project

team opted to monitor the building and share data on the CarbonBuzz platform (even though there was no fee to cover this work), a move more practices should consider.

‘An overlooked aspect of sustainability is the need to inspire and delight,’ Christophers told me as we departed. Each summer term, The King’s School, Worcester celebrates its rowers with a black tie dinner and awards evening. It’s hard to imagine a more magical spot for such a festivity than the prow of the boathouse with all doors thrown open overlooking the gardens’ herbaceous borders. n

Bottom left Diagonal sweet chestnut cladding makes a rich contrast with the English bond brickwork of the boat storeBelow Deep-set rooflights flood the ice birch-lined south wall, while north-facing sliding doors create a light-filled space

project data

start on site January 2011completion April 2012gross internal floor area 772m2form of contract Traditional JCTconstruction cost £1,859,000construction cost per m2 £1,772 structural engineer Shire Consultingm&e consultant Ledaqs Gwillam Darby Carrmain contractor Speller Metcalfeannual co2 emissions 9.01kg/m2 (measured)airtightness at 50pa 1.9m3/h.m2 (measured)on-site energy generation 20 per cent on-site: wood pellet and solar thermal (measured)annual mains water consumption 0.283m3/occupantannual heating and hot water load 13kWh/m2 (measured)overall area-weighted u-value0.19W/m2K

selected suppliers:bricks and prefabricated brick lintels ibstock warmcel 500; panelvent sheathing boards Excel Industriestriple-glazed and sliding doors Schücoenersign windows Green Building Storerooflights The Rooflight Companypavatherm plus woodfibre insulation boards Pavatex UK airtight membranes, gaskets, tapes Intello Plusframewrap breather membranes Dupont Tyvekironmongery Williams Ironmongery

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The boathouse occupies an ancient fortification line at the edge of Worcester’s historic centre. The detail shows the curved prow structure, cantilevered 5m over Riverside Walk.

Above the unheated 215mm-high brick base, the upper wall construction consists of timber I-beams with cellulose insulation injected under pressure to fill voids. Sweet chestnut laths of 32mm by 22mm, set at a 15° angle, are flexible enough to follow the curve. They wrap the prow and soffit while a curved ‘keel’ accommodates tapering steelwork. Ice birch-veneered ply panelling lines the internal walls, with acoustic slots tuning the teaching space.

Electrics run in a perimeter floor trunking with a removable timber lid. This allows future IT/rewiring to avoid conflict with the airtightness line. The screed floor provides a little thermal mass and is finished with 2mm self-smoothing resin, which reflects light from the windows and rooflights.John Christophers, associate, Associated Architects

Michael Baker Boathouse, The King’s School

Working detail

1. Terne-coated stainless steel standing seam roof finish, gutter and upstands

2. 100mm wood fibre breathable insulation board

3. 18mm WBP plywood decking

4. 300mm timber I-beams fully filled with blown cellulose insulation

5. Acoustic plasterboard ceiling

6. PPC aluminium capping

7. 32x22mm sweet chestnut laths with 4mm open joints fixed at 15° to horizontal with s/s pins

8. 50x50 sweet chestnut vertical battens at 600 centres

9. 400mm timber I-beams at max 600mm c/c fully filled with cellulose insulation

10. Breather membrane

11. 9mm high performance sheathing board manufactured from wood waste

12. Steel strap at 450mm centres supporting structural glazing on thermal isolating pads

13. EPDM membrane14. 12mm ice birch-

veneered ply panel

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15. Air-tightness and vapour control membrane

16. 150mm curved steel channel

17. Recessed roller blinds

18. 64mm triple-glazed frameless glass unit, bedded into channel taped to airtight membrane

19. 3mm satin stainless steel sill

20. 22mm maple window shelf, removable for access to trunking

21. Floor trunking for electrical/IT servicing

22. 100mm screed23. 200mm high

performance insulation

24. 150mm pre-cast concrete floor planks

25. 75mm steel supports at 450mm centres

26. 150mm perimeter curved steel channel spanning cantilevered stub beams

27. SW timber profiles at 450mm centres

28. Sweet chestnut soffit with joints mitred to line through with walls

29. 215mm English bond facing brick wall with 440mm stretchers

Associated Architects

Prow section detail